Public health management of cases and contacts associated with COVID-19  

Updated December 24, 2021

This guidance is informed by the latest available scientific evidence, epidemiology and expert opinion, and is subject to change as new information becomes available.

Note

This page is continually under review and updated as the COVID-19 pandemic evolves. Updates have been made to the last version (July 5, 2021) in the following sections:

The updates in this version:

Please visit the provincial and territorial resources for COVID-19 page for updated guidance specific to your province or territory

On this page

Introduction

The Public Health Agency of Canada (PHAC), in consultation with Canadian public health experts, has developed this guidance for federal/provincial/territorial (FPT) public health authorities (PHAs) to support the management of individuals infected with or who may have been infected with the SARS-CoV-2 virus (i.e., "cases") and contacts of COVID-19 cases within their jurisdictions. It is recognized that PHAs may adjust case and contact management recommendations based on a risk assessment that would include:

The strategy outlined in this guidance focuses on case and contact management to mitigate the health impacts of COVID-19 on individuals in Canada Footnote1. This guidance is set in the Canadian context and is based on the available scientific evidence and expert opinion. In interpreting and applying this guidance, it is important to recognize that the health, disability, economic, social, or other circumstances faced by some individuals and households may limit their ability to follow the recommended measures. This may necessitate adapted case management and contact responses by PHAs.

Impact of vaccination

Evidence suggests that a single vaccine dose offers some protection against SARS-CoV-2 infection Footnote2, and that two doses of vaccine (including both mRNA and other vaccine types) are moderately to highly effective against asymptomatic and symptomatic SARS-CoV-2 infection in the short-term Footnote2 Footnote3 Footnote4. Vaccines offer very high protection against severe outcomes, such as hospitalization and death Footnote2 Footnote3 Footnote4. Evidence on the effectiveness of COVID-19 vaccines authorized for use in Canada is summarized in the National Advisory Committee on Immunization's (NACI) COVID-19 vaccine statements which are updated as evidence evolves.

While COVID-19 vaccines reduce the risk of infection, vaccinated individuals may still become infected (these are known as breakthrough infections). Emerging evidence suggests that vaccine-induced protection against SARS-CoV-2 infection may decrease over time, which may be due to decreased circulating antibodies Footnote5 Footnote6 Footnote7. However, despite decreased protection against infection over time, the risk of severe disease in vaccinated individuals remains significantly lower compared to unvaccinated individuals Footnote8 Footnote9 Footnote10 Footnote11. This may be due to the fact that while circulating antibodies are reduced, the immune memory responses appear to be retained over time Footnote12. To address decreasing protection against infection over time, some countries, including Canada, have started offering booster doses, with the intent that they will restore protection that may have decreased over time. More research is needed to fully understand long-term vaccine-derived immunity and research regarding booster vaccines and the ideal dosing schedule is ongoing. PHAC will continue to monitor evidence related to vaccine effectiveness and the protection provided by booster doses, and assess how this affects public health measures advice.

Impact of variants of concern

The response to the COVID-19 pandemic has been strengthened by the availability of vaccines, but is further challenged by the emergence of VOCs within Canada and worldwide (e.g., the Delta and Omicron variants) and uncertainties surrounding their characteristics at the time of initial identification.

Mutations in the SARS-CoV-2 virus that result in it being designated as a VOC are those which may cause:

Changes in these characteristics can have implications for public health case and contact management activities.

Adjusting public health measures

Provincial and territorial (PT) PHAs continue to adjust public health measures based on the epidemiology of COVID-19 and vaccination coverage in their jurisdictions, and other important indicators. Some of these indicators include sufficient public health capacity to test, trace, isolate or quarantine a high proportion of cases and contacts, respectively; sufficient health care capacity to respond to surges; and risk reduction measures in place for high-risk populations (i.e., those at risk of more severe disease or outcomes) and settings.

This guidance is subject to change as new information on VOCs, vaccine effectiveness and dynamics of decreased protection against infection over time, transmissibility and epidemiology becomes available. It should be read in conjunction with relevant PT and local legislation, regulations and policies. Coronavirus disease (COVID-19) outbreak updates are available.

Case management

Reporting and notification

The national case definition for COVID-19 provides surveillance case definitions as well as associated surveillance reporting requirements.

It is important for frontline health care providers to notify PHAs of cases of COVID-19 in accordance with jurisdictional reporting requirements. PHAs need to provide overall coordination with health care providers and provincial laboratories for the management and reporting of cases, and to establish communication links with all involved health care providers for the full duration of illness. PHAs may voluntarily report confirmed cases of COVID-19, as well as probable cases where feasible, to PHAC within 24 hours of receipt of their own notification. National surveillance for Coronavirus disease (COVID-19) guidance is available.

In some instances, cases or contacts are identified with epidemiological linkages that span two or more jurisdictions within and/or between provinces/territories. During case investigation, it may also be identified that the case acquired their infection, or was potentially exposed, in another jurisdiction. PHAs should use established inter-jurisdictional processes to enable timely case and contact management. Examples where this may be required include when a case travelled between jurisdictions during their communicable period; or when contacts reside in a different jurisdiction than a case.

Laboratory testing and screening

Laboratory testing strategies have evolved over time. Each PT has modified their approach (e.g., who is being tested and how) based on factors such as emerging evidence, new technology, laboratory capacity and local epidemiological circumstances. Information is available on the important roles that FPT governments play in COVID-19 testing.

At present, a validated reverse transcription polymerase chain reaction (RT-PCR) test on a clinically appropriate sample collected by a trained health care provider is the gold standard for the diagnosis of SARS-CoV-2 infection.

Appropriate laboratory testing for COVID-19 infection should be accessible by health care providers through community-based, hospital or reference laboratory services (e.g., a provincial public health laboratory (PHL) running a validated assay), or the National Microbiology Laboratory (NML). In addition, PTs should have a process for screening and sequencing positive specimens for mutations common to VOCs. The establishment of screening assays looking for mutations specific to VOCs can provide results sooner than sequencing of virus samples and may be useful for informing timely public health action. However, not all VOCs will have common mutations so surveillance using partial or whole genome sequencing must be established by the PT. The NML provides guidance to PHLs on the sample strategies for sequencing of positive specimens, updated based on the shifting risk from variants in an increasingly vaccinated population. A minimum baseline surveillance approach based on randomized selection of specimens, including samples from both vaccinated and unvaccinated individuals, is recommended. Within capacity limit, it is recommended that specimens from travelers, outbreaks and patients admitted to hospital should be prioritized.

Guidance for health professionals related to laboratory testing is available. In addition, the Respiratory Virus Infections Working Group of the Canadian Public Health Laboratory Network has developed laboratory testing best practices for COVID-19 and has updated its protocol on microbiological investigation of emerging respiratory pathogens, including severe acute respiratory infections Footnote13 Footnote14.

Rapid testing for COVID-19 using non-molecular assays has the potential to increase testing capacity; however, current data suggest that these methods are less sensitive than the current RT-PCR assays Footnote15. The quick turn-around times and ease of use by a wide range of users allows rapid testing to be an important tool in a broader testing strategy (e.g., rapid testing of asymptomatic individuals in a cohort in which an outbreak is occurring or as part of a broader community-based testing strategy to help bring community transmission under control) Footnote16. Interim guidance is available for use of the nucleic acid- and antigen-based rapid detection tests.

Re-infection

There is evidence that individuals can become re-infected with SARS-CoV-2 Footnote17 Footnote18. The dynamics, duration, and nature of immunity produced during infection with SARS-CoV-2 are still unclear, but there is good evidence of immunity for at least several months in the majority of individuals previously infected Footnote19 Footnote20 Footnote21. The evidence will be monitored to determine if there is a higher risk of re-infection associated with VOCs, which may impact future guidance on testing. Refer to guidance for laboratory testing for individuals suspected of being re-infected for more information.

Clinical management/treatment

Clinical management of the case, whether in the home or in an acute care setting, is based on the case's condition and at the discretion of the case's health care provider. COVID-19 signs, symptoms and severity of disease: A clinician guide is available to inform clinicians on what is presently known about the clinical features of COVID-19, including signs and symptoms, incubation period, disease severity and risk factors for severe disease, SARS-CoV-2 VOCs and reinfection.

Health care providers involved in home care for a case should follow interim guidance developed for infection prevention and control in home care settings. Guidance for household members providing care for a case in the home, or occupants/staff in a co-living setting, are detailed in Appendix 1.

Case management in the community

Epidemiologic evidence suggests that the majority of people with COVID-19 do not require care in a hospital Footnote22. When care in a hospital is not required, cases should isolate themselves as soon as possible. If they are isolating in the home or co-living setting (e.g., student residence, group home, shelter, etc.), they should isolate away from other household members or occupants, as directed by their PHA.

Those who live alone, or in a home where the members of the household are in isolation or quarantine, should identify community and social supports (e.g., family, friends, social services) where possible to assist with essential needs, including care of pets when required, or consult with their local PHA for information about additional community resources.

Appendices 1 and 2 provide information regarding recommendations for isolation and assessment of a suitable isolation location, respectively.

Seeking medical care

In the event of a medical emergency, the case or their caregiver should contact emergency medical services (911) or the local emergency helpline for medical assistance, including transportation to the hospital or clinic if necessary. If using an ambulance to travel to a hospital or clinic, inform the dispatcher that the person requiring medical care has COVID-19. Public transportation should not be used to seek medical care (if possible).

If using a private vehicle to seek medical care:

Isolating in the community

When advising individuals to isolate in the community-at home or in a co-living setting-it is important that the risk of transmission from the case to other members of the household or occupants in the co-living setting be minimized as much as possible.

Guidance for isolating at home or in other co-living settings, as well as recommendations when strict adherence to isolation requirements may not be possible, are available in Appendix 1.

Assessing suitability for isolation in the community

The PHA, in collaboration with the case and their health care provider, will determine the location where a case of COVID-19 isolates, as appropriate. It is important that cases who do not require hospital-level care convalesce in a suitable environment where effective isolation can be maintained and appropriate monitoring (e.g., for worsening of illness) can be provided.

Considerations for a suitable environment will depend on the individual and their living situation; and may vary depending on the sex, gender, or other socioeconomic or identity factors of the case. The vaccination status of other household members may also be taken into consideration.

The PHA plays an important role in assessing the suitability of the case's isolation setting, and the considerations listed above are detailed in Appendix 2.

Psychosocial considerations

It is recommended that PHAs encourage individuals, families and communities to create a supportive environment for people who are isolating to take care of their mental health, and minimize stress and hardship associated with isolation as the financial, social, and psychological impact can be substantial.

Obtaining and maintaining public trust are key to successful implementation of these measures. Clear messages about isolation, including the criteria, rationale, justifications, and duration, as well as ways in which persons will be supported during the isolation period, will help to generate public trust. Messaging should also be sensitive and tailored to the needs of populations confronting social, economic, cultural or other vulnerabilities. Additional information on the psychological impacts of COVID-19 is available.

For Indigenous Peoples, mandatory isolation away from home due to COVID-19 may trigger re-traumatization issues associated with experiences of forced removals in the past. There is also the potential for new trauma if their ability to be with their community, practice cultural and/or spiritual activities is limited. To avoid relocation of persons with COVID-19 to locations outside of their community, many Indigenous communities have re-purposed facilities or set up temporary structures to use as isolation sites so that community members may safely isolate in situations where their home setting is not suitable.

Public health monitoring of cases

It is recognized that the frequency of monitoring of COVID-19 cases may vary by PHA and the local context, but generally, monitoring should include the following assessments or advice:

PHAs should provide additional information about VOCs as required, such as when VOCs are circulating in the community or when a case has been diagnosed with a variant strain, including heightened vigilance for increased transmissibility if isolating at home or in a co-living setting with other household members or occupants.

Cases of COVID-19 should be monitored until they have met the criteria set by the PHA for discontinuing isolation.

Discontinuation of isolation for cases in the community

The PHA should direct the discontinuation of isolation of cases in the community (i.e., those not hospitalized or residents of long-term care facilities) Footnoteb. Criteria may include:

In general, repeat laboratory testing (e.g., a negative test result) as the basis for discontinuing home isolation is not recommended. In most individuals with competent immune systems and those recovered from mild or moderate illness, prolonged or renewed RNA detection is not believed to reflect infectious virus, but rather non-infectious viral fragments, as viable virus has rarely been reported to persist for longer than 10 days in these populations. Additional information can be found in Guidance for repeated PCR testing in individuals previously positive for COVID-19.

There may be exceptions to these criteria for which PHA and/or clinical care providers may determine a longer isolation period is warranted (e.g., immunocompromised individuals, those hospitalized due to COVID-19). Discontinuation of isolation is not related to clinical management of cases. For some cases, clinical management may continue to be required after discontinuation of isolation.

Contact management

Contact management for community-based cases of COVID-19 is the responsibility of local and provincial PHAs, and has evolved as vaccine coverage in Canada has increased.

It continues to be important to identify and manage the contacts of cases of COVID-19 to reduce ongoing transmission of the virus in the community Footnote24, particularly with the presence of VOCs in Canada (e.g., the Delta and Omicron variants), as well as the implications around decreased protection against infection over time and breakthrough infections among vaccinated populations. Several objectives may be achieved through contact management activities by PHAs, including:

Early identification of contacts, and direction regarding diagnostic testing for COVID-19 based on existing PT testing strategies, is a key component of rapid case identification and management to reduce transmission of SARS-CoV-2. With the many unknowns associated with VOCs, testing of vaccinated individuals will be an important consideration of contact management.

In an outbreak context, contact tracing and management also serves the purpose of active case finding during an investigation. Where an outbreak is suspected, the PHA may adopt a situation-specific definition for those at high risk of exposure (i.e., "close contact") to help efficiently target their contact investigation and case finding efforts. For example, all individuals at an event associated with a high risk of transmission could be evaluated as being at high risk of exposure (e.g., all guests at a wedding, or participants of an indoor fitness class). This approach may be considered when the outbreak setting results in a high risk of exposure for most participants, or where risk assessments for individuals are not feasible.

Outbreaks may have a greater impact on certain groups due to their social, economic, health, or other risk factors, such as older age, having chronic medical conditions, living in a remote and isolated community, or living in poverty or crowded settings.

PHAs should give consideration to engaging in more rigorous outbreak investigation activities when an outbreak involves a VOC. This may include backward contact tracing or mass asymptomatic testing of individuals with known or suspected close contact exposure to a case with a VOC.

Contact tracing

The public health approach to COVID-19 case and contact management has largely focused on interrupting chains of transmission through contact tracing by identifying individuals at risk of exposure to SARS-CoV-2 from an identified case. The primary goal of contact tracing is to identify and to quarantine, or to facilitate self-monitoring of, individuals who are potentially exposed to a case to stop future chains of transmission.

Contacts should be identified and managed as per the recommendations in this document, where feasible based on public health resources. The level and intensity of public health actions may vary among jurisdictions according to the local epidemiology of COVID-19 at a given time and the identification of VOCs. Alternative contact management strategies that PHAs may consider when resources are constrained are detailed below.

The risk assessment conducted by the PHA can help identify each contact's exposure risk level, determine the appropriate intervention for the individual (e.g., quarantine, self-monitoring) and PHA actions for the recommended monitoring period. If the contact has been vaccinated, the PHA risk assessment may consider additional factors that could influence risk categorization and subsequent PHA actions (see Important considerations in Table 1 below). In addition, if there are newly circulating VOCs within the community or there is uncertainty about the risk assessment for a contact of a case infected with a VOC, PHAs may choose to adopt a more cautious approach when managing contacts as either high- or low-risk of exposure (see Table 1 below).

Given that transmission of SARS-CoV-2 can occur from cases who are symptomatic, pre-symptomatic, or asymptomatic, contact tracing should include:

For operational purposes, a minimum period of 48 hours prior to symptom onset (or positive test result) should be considered by jurisdictions for contact tracing. Under certain circumstances (e.g., outbreak management, VOCs, backward contact tracing), jurisdictions may extend contact tracing greater than 48 hours prior to symptom onset (or positive test result) when public health capacity and/or the risk assessment warrants it.

Table 1 provides guidance for classifying contacts as either high or low risk, depending on their exposure, for the purposes of determining recommended actions. The information provided in Table 1 is not intended to replace more personalized public health advice provided to contacts, based on comprehensive risk assessments conducted by PHAs.

Note that fully vaccinated in this context means at least 14 days have passed since the completion of the recommended number of doses of a Health Canada approved COVID-19 vaccine or fully vaccinated as defined in the jurisdiction.

Table 1: Contact management recommendations by exposure risk level

Note: In determining exposure risk level, all potential exposures described below are considered to have occurred when the case was communicable.

Important considerations: The high and low risk exposure categories in Table 1 offer a simple guide for assessing a contact's risk of exposure to COVID-19 during contact tracing. In reality, there is a spectrum of risk, where adherence to public health risk mitigation measures helps to decrease the chance of infection. A risk assessment conducted by the PHA may further inform personalized recommendations.

When assessing risk to fully vaccinated contacts, PHAs may consider:

The risk assessment may also consider individual-level risk mitigation measures, including adherence to individual public health measures (e.g., mask wearing, hand hygiene, physical distancing, etc.) by both the case and the contact.

When determining exposure risk level, setting-specific considerations would include those places where a contact was potentially exposed, including whether the exposure was indoors (higher risk) or outdoors (lower risk), ventilation quality, the size and number of people in the setting, and risk mitigation measures in place in the setting (e.g., requirements for wearing masks, physical distancing, cleaning high-touch surfaces, etc.) Footnote27.

Although outdoor settings are generally considered lower risk, the potential for transmission still exists under certain circumstances, such as close conversations or rigorous exercise when individuals are in close proximity and are not wearing masks and could be taken into account when conducting a risk assessment Footnote27.

Risk Level

Description

Recommendations for the contact

High risk exposure (close contact)

  • HCW who is not fully vaccinated and who provided direct physical care to a case, or a laboratory worker handling COVID-19 specimens, without consistent and appropriate use of recommended PPE and infection prevention and control practices Footnotec.
  • Anyone who is not fully vaccinated and lives with a case, has direct physical contact with a case, or is exposed to their infectious body fluids, including the case's caregiver, intimate partner, child receiving care from the case, etc.
  • Anyone who is not fully vaccinated and has shared an indoor space (e.g., same room) with a case for a prolonged period of time Footnoted, including closed spaces and crowded places, (e.g., social gatherings, workplaces, etc.), without adhering to appropriate individual-level and setting-specific risk mitigation measures (see Important considerations above).
  • Anyone who is not fully vaccinated and has had a close-range conversation with a case or has been in settings where a case engaged in singing, shouting, or heavy breathing (e.g., exercise), without adhering to appropriate individual-level and setting-specific risk mitigation measures (see Important considerations above).
  1. Quarantine at home for 14 days from last exposure or for the recommended period determined by the local PHA (see Appendix 4)
  2. Follow recommended individual public health measures. Contacts should wear a respirator (or if not available, a well-fitted medical mask) Footnotea. If living with the case, avoid further exposure to the case (see Appendix 4).
  3. Follow PHA directions related to testing requirements Footnotee.
  4. Self-monitor for the appearance of symptoms consistent with COVID-19 for 14 days following their last exposure to the case.
  5. Take and record temperature daily and avoid the use of fever-reducing medications (e.g., acetaminophen, ibuprofen) as much as possible. These medications could mask an early symptom of COVID-19; if these medications must be taken, advise the PHA Footnote28.
  6. If symptoms occur, isolate away from others within the home or co-living setting as quickly as possible; put on a respirator (or if not available, a well-fitted medical mask) Footnotea and contact the PHA for further direction, which will include:
    • where to go for care,
    • appropriate mode of transportation to use, and
    • IPC precautions to be followed.
  7. Avoid in-person interactions with others, especially those who are at risk for developing more severe disease or outcomes from COVID-19.
  8. Household members who are at risk for developing more severe disease or outcomes should not provide care for the case and should avoid further exposure.

Low risk exposure

  • HCW (regardless of vaccination status) who provided direct physical care to a case, or a laboratory worker handling COVID-19 specimens, with consistent and appropriate use of recommended PPE and infection prevention and control practices Footnotec.
  • Anyone (regardless of vaccination status) who has shared an indoor space (e.g., same room) with a case, including closed spaces and crowded places (e.g., social gatherings, workplaces, etc.), with adherence to appropriate individual-level and setting-specific risk mitigation measures (see Important Considerations above).
  • Anyone (regardless of vaccination status) who has had a close-range conversation with a case or has been in settings where a case engaged in singing, shouting, or heavy breathing (e.g., exercise), with adherence to appropriate individual-level and setting-specific risk mitigation measures (see Important considerations above).
  • While acknowledging the important considerations listed at the beginning of this section (Table 1), fully vaccinated individuals in the above-mentioned high-risk exposure (close contact) situations would be considered to have a low risk exposure and be managed accordingly.
  1. Self-monitor for symptoms for 14 days following their last exposure.
  2. If symptoms occur, isolate away from others as quickly as possible, put on a respirator (or if not available, a well-fitted medical mask) Footnotea and contact the PHA for further direction, which will include:
    • where to go for care,
    • appropriate mode of transportation to use, and
    • IPC precautions to be followed.
  3. Where possible, avoid interactions with individuals at higher risk for severe illness (this may not apply to HCWs who are using PPE and following IPC practices appropriately in their workplace) Footnotec.
  4. Follow PHA directions related to testing requirements.
  5. Follow recommended individual public health measures.

Acronyms:

  • HCW: health care worker
  • PPE: personal protective equipment
  • IPC: infection prevention and control

Although transmission of SARS-CoV-2, including VOCs, may occur during brief exposures, transient interactions (e.g., walking by a case) have not been identified as high- or low-risk exposures in Table 1 because identifying such contacts is typically not feasible outside of digital contact tracing applications (see Alternative contact management strategies below).

Based on a risk assessment, PHAs may consider more robust approaches to contact management and quarantine specifications, particularly in the context of outbreak investigations involving VOCs. See the Enhanced case and contact management section below for more detail.

PHAs may also need to consider modifications to quarantine recommendations in some circumstances, such as the need for essential workers to maintain critical services. In these circumstances, jurisdictions may consider reducing quarantine with negative test results. At present, there is limited evidence to support this as a widespread approach, as there remains a residual risk of transmission Footnote29.

The duration of contact management for a contact who develops symptoms compatible with COVID-19 within 14 days of last exposure to a case should be based on the following considerations.

Alternative contact management strategies

To complement or accommodate limited local resources, PHAs may consider alternative approaches to traditional contact tracing, particularly when they are experiencing a local surge in cases Footnote30. These may include the following:

During local peaks in COVID-19 activity and declared outbreaks, PHAs may also consider prioritizing contact tracing activities for specific settings where people gather (e.g., schools, events, workplaces, remote communities, etc.), and in particular, when epidemiologic features suggest a change in transmission dynamics (e.g., when a VOC is suspected or confirmed). PHAs may also consider prioritizing follow-up of contacts (e.g., those with vulnerabilities, those who work in high-risk settings, or those who provide care to someone with vulnerabilities, etc.) Footnote30. PHAs may also consider alternative approaches where cases, employers, or event coordinators notify contacts (i.e., simple referral); or notify contacts and provide additional information related to infection prevention and control, quarantine, and symptom monitoring (i.e., enhanced referral) Footnote31.

Backward contact tracing

PHAs may also consider 'backward' contact tracing, which focuses on trying to determine where and when the case likely acquired their infection. Backward contact tracing is routinely done as part of case or outbreak investigations for communicable diseases of public health significance, when PHAs collect information on a case's potential acquisition history (i.e., source investigation). In this guidance, backward contact tracing is proposed as a less intensive activity, and therefore potentially less resource intensive, compared to outbreak investigation.

While COVID-19 has been observed to spread steadily in the community, with one case infecting one or two other individuals on average, clusters have been identified where some individuals disproportionately infect a larger number of individuals. This represents a statistical concept called over-dispersion, where roughly 10% of COVID-19 cases are responsible for up to 80% of secondary infections Footnote32 Footnote33. Clusters associated with these cases have been referred to as super-spreading events (SSEs).

VOCs resulting from mutations in the genetic code of SARS-CoV-2 can cause the virus to act in ways that have significant impacts on case and contact management (e.g., increases in transmissibility or severity; its ability to become undetectable by tests; or the effectiveness of vaccines or treatments).

In these circumstances, 'backward' contact tracing may help to:

If the source case is identified through backward contact tracing, contact tracing to identify individuals who may have been exposed to a case should be employed as detailed above, and contacts managed based on their risk of exposure as described in Table 1. Depending on a given situation, testing requirements and public health interventions may need to be scaled based on local epidemiology.

Backward contact tracing is considered to be most useful when localized outbreaks may be occurring in areas experiencing relatively low levels of transmission. It may also be considered for investigating outbreaks with an epidemiologic feature suggestive of change in transmission dynamics (e.g., where a VOC is implicated).

It is considerably more challenging when there is widespread community transmission, due to the volume of cases and uncertainty created by having multiple potential sources of transmission for any given case. Employing backward contact tracing approaches may have significant resource implications, depending on the specific contact tracing strategies used, approaches to testing, and local epidemiology.

There is growing evidence regarding the effectiveness of backward tracing for COVID-19; however, additional research is still needed on when it would be most useful or how it would be best implemented Footnote34 Footnote35 Footnote36 Footnote37. A limited number of countries have utilized this strategy, and beneficial impact was correlated with low incidence and limited community transmission Footnote38 Footnote39. PTs should consider the utility of backward contact tracing based on their individual circumstances and available resources and, if implemented, consider evaluating the effectiveness in order to contribute to the evidence base for this practice.

Persons possibly exposed during travel

In response to the COVID-19 pandemic, all travellers entering Canada are subject to the rules set out by the emergency orders under the Quarantine Act.

Current information regarding travel, testing, quarantine and borders requirements can be found at COVID-19: Travel, testing, quarantine and borders.

History of travel should be considered by PHAs during a risk assessment during contact tracing.

Contact tracing for airplane passengers and flight crew

Potential exposure to SARS-CoV-2 among passengers and crew during air travel is a topic of concern; however, risk mitigation measures such as vaccination status, mandatory use of masks, physical distancing, ventilation, environmental cleaning, hand hygiene, and reduced occupancy, applied in a layered approach, can significantly reduce the likelihood of transmission Footnote40.

Decisions related to contact tracing individual airplane passengers and flight crew who may have been exposed to a confirmed case of COVID-19 on any flight should be made based on available resources and a risk assessment. Risk assessments should be conducted by the PHA to which the case is notified, considering the following:

If the PT determines that notification to potential contacts is required, the PHA can follow local protocols for publicly communicating when a SARS-CoV-2 case travelled during the period of infectiousness. The information required is the flight number, flight date, departure/arrival locations, and affected rows of the flight.

Enhanced case and contact management considerations

There are some situations when a PHA may implement enhanced case and contact management protocols. For example, when a VOC poses significant risk (i.e., due to increased transmissibility, severity of disease and potential for immune escape), or when a newly circulating VOC has first been identified - either internationally or domestically - and there is limited scientific evidence available on its characteristics.

There may be a period of time between identifying a case and receiving laboratory confirmation of a VOC. In some circumstances, PHAs may not require laboratory confirmation to implement enhanced case and contact management strategies.

Enhanced case and contact management protocols may include:

Over time, if the VOC becomes more widespread and/or new evidence indicates the VOC does not pose a significant risk, PHAs may scale down their case and contact management activities accordingly.

Appendix 1: Recommendations for isolation of COVID-19 cases in the community

When care in a hospital is not required, cases of COVID-19 should isolate themselves as soon as possible. If they are isolating in the home or co-living setting (e.g., shelter, group home, or student residence), they should isolate away from other household members or occupants, as directed by their PHA. It is recommended the case isolate in a separate room for sleeping with access to a separate washroom from other household members or occupants, if possible. When feasible and as directed by the PHA, cases could isolate in an alternate dwelling such a hotel or self-containing unit. They should isolate for a minimum of 10 days from the onset of symptoms for a symptomatic case, or the collection date of a positive specimen for an asymptomatic case.

During isolation, the case should not leave the isolation setting, whether it is their home, co-living setting, or an alternate setting identified by their PHA or health care provider. They should:

Isolating in the community

When advising individuals to isolate at home or in a co-living setting, it is important that the risk of transmission from the case to other members of the household or occupants in the co-living setting be minimized as much as possible. Advice is available for individuals who are required to isolate at home due to COVID-19 .

As much as possible, the following strategies should be used during isolation in the community.

Recommendations when strict isolation is not possible

Cases of COVID-19 who have been directed to isolate may not be able to strictly follow instructions for isolation in the home or co-living setting. This may be due to the isolation setting itself, for instance, there are not enough rooms in the home for the case to have a separate room or a dedicated washroom, or occupants in a shelter who must share space. It may also be difficult to isolate due to other factors; for example, if the case is a child, has child-/elder- care responsibilities, or lives in a multigenerational household.

When it is not possible to relocate the case, or members of the household or co-living setting, the following approaches may be considered:

Appendix 2: Assessment of a suitable isolation location for a case of COVID-19

The location where a COVID-19 case will be isolated should be determined by the PHA, in collaboration with the case and their health care provider, as applicable. It is important that cases who do not require hospital-level care convalesce in a suitable environment where effective isolation and appropriate monitoring (e.g., for worsening of illness) can be provided.

Considerations for a suitable environment will depend on the individual and their living situations, and may vary depending on the sex, gender, or other socioeconomic or identity factors of cases.

Factors to consider when determining the suitability of an isolation location:

Can the case's clinical condition be managed as an outpatient?

For isolation in the community, including the home or a co-living setting (e.g., shelter, group home, student residence, etc.), it must be possible to manage the case as an outpatient, taking into consideration their baseline health status and the presence of risk factors for more severe disease or outcomes. If hospitalization is required (e.g., due to worsening condition, health emergency, direction of health care provider), home isolation will no longer be feasible.

Is the case able to manage their own care?

Cases should be able to monitor themselves for new or worsening symptoms; take appropriate action as advised by the PHA or their health care provider, including self-care; properly wearing a respirator (or if not available, a well-fitted medical mask) Footnotea; maintaining appropriate individual public health measures (e.g., maintaining proper hygiene practices, clean and disinfect high-touch surfaces, etc.), and isolating away from others.

A case's ability to manage their own care may be impacted by various factors, including:

Does the case require care? Is someone available to provide the care?

Some circumstances may require a household member to provide care to the case; for example, when the case is a child, an elderly relative who requires support, or a case who is very ill. When this occurs, the following should be considered:

What are the characteristics of the home or co-living configuration?

Cases may be in various household configurations that may hinder their ability to isolate themselves. For instance, the case may be a single-parent who must provide care to a child, or they may live in a multi-generational home with shared child- and elder-care responsibilities. If the case provides care to a child where childcare is shared between parents in two separate homes, consideration should be given to the most appropriate location for the child while the case is isolating.

If the case is isolating in their home or co-living setting, they should isolate away from others as soon as they are notified they have or may have COVID-19. Special consideration is also needed to support cases living in homes where it is difficult to separate from others (e.g., a one-bedroom apartment), or are living in co-living settings, such as student residence, shelters, and overcrowded housing. The preferred option is to provide the case in these settings with a single room and a private washroom. In some situations, based on a thorough risk assessment, PHAs may advise relocation of either the case or other household members to another location (e.g., hotel, self-containing unit), if feasible. Relocation will be dependent on a variety of factors, including guidance from the jurisdiction's PHA, financial support, and availability of alternate spaces.

If it is not possible to provide the case with a single room and a private washroom in the co-living setting, efforts should be made to cohort confirmed cases together. For example, if two cases reside in a co-living setting and single rooms are not available, they could share a double room.

Are there others with greater risk of more severe disease or outcomes in the home or co-living setting?

Household members, or other occupants in co-living settings, who are at risk for more severe disease or outcomes from COVID-19 should not be in a shared space with or provide care to the case and alternative arrangements may be necessary. This could include temporarily relocating these individuals or the case outside of the home to an alternate location determined by public health, such as a designated hotel.

Is the home or co-living setting suitable for isolation?

The PHA can determine if the home or co-living setting is suitable for isolation of the case. Cases may live in settings where they lack available space to provide a dedicated room and private washroom for the case, such as an overcrowded house, student residence where the case has a roommate, or a homeless shelter. Housing conditions should also be assessed, including access to potable, running water, and the state of repair of the home. Safety of the setting should also be assessed in terms of the potential occurrence of gender-based or family violence or other abuse.

Can the case access adequate supplies and necessities?

Consider whether the case has access to supplies and necessities for the duration of isolation, such as food, running water, drinking water, supplies for infection control (e.g., masks), and cleaning supplies. A list of supplies to have on-hand while isolating is available. Those residing in remote and isolated communities may wish to consider stockpiling the needed supplies, as well as food and medications, if it is likely that the supply chain may be interrupted or unreliable.

A case who does not have access to adequate food or necessary supplies could contact local leadership, public health or organizations that provide direct support. Guidance is available for hand washing in the absence of running or clean water.

If the home or co-living setting is inadequate for home isolation based on the assessment, it is recommended PHAs collaborate with the case and their health care provider, to determine a more suitable location. This may involve relocating the case to a more suitable community setting, hospitalizing the case, or accessing additional community supports and resources where available.

Appendix 3: Recommended infection prevention and control precautions when caring for a case in the home or co-living setting

Anyone who provides care to a case of COVID-19 should wear a respirator (or if not available, a well-fitted medical mask) Footnotea, as well as use eye protection whenever providing care. Caregivers should also frequently wash their hands, especially when in direct contact with the ill person or their environment, including soiled materials and surfaces.

Advice is available to support those caring for someone with COVID-19 at home:

Eye protection

Eye protection is recommended to protect the mucous membranes of the caregiver's eyes while providing care to a case of COVID-19, or during any activities likely to generate splashes or sprays of bodily fluids, including respiratory secretions.

Gloves

Caregivers do not have to wear disposable single-use gloves when caring for someone in the home setting. Frequent hand washing is preferred.

It is recognized, however, that some caregivers may still choose to wear disposable single use gloves, when in direct contact with the ill person, cleaning contaminated surfaces, and handling items soiled with bodily fluids, including dishes, cutlery, clothing, laundry, and waste for disposal.

Gloves are not a substitute for hand hygiene; caregivers must perform hand hygiene before and after putting on and taking off gloves.

Appendix 4: Recommendations for quarantine in the community

In general, quarantine means that a contact stays in their home and does not go out, and avoids in-person interactions with others, including their household members.

The quarantine period typically aligns with the period of communicability. However, PTs may opt to implement a reduced quarantine period in combination with testing protocols, depending on the risk assessment and local circumstances.

A contact should quarantine away from other household members or occupants, as directed by their PHA. If the contact lives with the case, they should avoid further exposure to the case as well. It is recommended the contact quarantine in a separate room for sleeping with access to a separate washroom from other household members or occupants, if possible. In some situations, based on a thorough risk assessment, the PHA may advise a contact to quarantine in an alternate dwelling such a hotel or self-containing unit, if feasible.

A contact should wear a respirator (or if not available, a well-fitted medical mask) Footnotea, whenever using a living space that may be accessed by others (e.g., a hallway, kitchen, washroom). If the contact requires care during their quarantine period (e.g., a young child or older adult), their caregiver should also wear a respirator (or if not available, a well-fitted medical mask) Footnotea. Any household members living with the contact should wear a respirator Footnotea when sharing a space with them.

This is especially important for household members who are at risk of more severe disease or outcomes, or if they are living in an overcrowded setting.

For contacts in quarantine who are living with a case, the PHA will determine when their quarantine period begins by assessing the characteristics of the setting. If it is determined that there is adequate separation between the case and the contact, the PHA may advise that the contact’s quarantine period begins the day the case goes into isolation. If there is inadequate separation (e.g., shared sleeping quarters, shared washroom, etc.), the PHA may require the contact to quarantine for the duration of the case's isolation period, plus up to an additional 14 days afterwards.

If additional members of a household with a case become ill, the PHA should assess whether other asymptomatic household members need to quarantine based on their last exposure to the new case.

Acknowledgments

This technical guidance was developed in consultation with the Canadian Pandemic Influenza Preparedness (CPIP) Task Group and with federal, provincial and territorial partners via the Technical Advisory Committee (TAC) and/or the Special Advisory Committee (SAC). This guidance was also developed in consultation with other government departments, various multilateral partners, Indigenous stakeholders, and other external stakeholders with an interest in this subject matter.

Footnotes

Footnote a

In situations where respirators or medical masks are recommended but not available, the individual should properly wear a well-constructed and well-fitting non-medical mask.

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Footnote b

For additional information, refer to:

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Footnote c

This guidance is focused on community settings, and does not replace point-of-care risk assessments by health care providers in health care settings, or a risk assessment conducted by PHAs to determine the exposure risk for a health care worker (HCW).

Guidance related to the appropriate use of personal protective equipment (PPE) and infection prevention and control for HCWs and laboratory workers is available. See the following guidance documents:

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Footnote d

There is insufficient evidence available to define risk in terms of the length of exposure time required for transmission. For public health contact identification and management purposes only, a period of 15 cumulative minutes over 24 hours has been selected to distinguish between brief and prolonged exposure. This same period has been used in other countries Footnote30 Footnote45 Footnote46. This parameter should not replace the conclusions derived from a risk assessment, conducted by the public health authority, that addresses a variety of factors (i.e. infectiousness of the case at time of exposure, exposure is to a VOC, likely route of transmission, risk factors, etc.) that will more precisely inform risk.

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Footnote e

Jurisdictional specific testing policies/capacity could have implications on individual quarantine recommendations within that jurisdiction.

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Footnote f

The 2-metre parameter should not replace the conclusions derived from a risk assessment conducted by the PHA that addresses a variety of factors (e.g., infectiousness to the case at time of exposure, exposure is to a VOC, the likely route of transmission, increased risk of more severe disease or outcomes) that will more precisely inform risk.

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Footnote g

For operational purposes, an appropriate physical distance is at least 2 metres. In general, if in-person interactions must take place, individuals should be encouraged to interact from the greatest distance possible, and with other individual public health measures in place for a layered approach.

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References

Footnote 1

Public Health Agency of Canada, "Public health measures: Canadian Pandemic Influenza Preparedness: Planning Guidance for the Health Sector," December 2018. [Online]. Available: https://www.canada.ca/en/public-health/services/flu-influenza/canadian-pandemic-influenza-preparedness-planning-guidance-health-sector/public-health-measures.html#a354. [Accessed 10 December 2021]

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Footnote 2

National Advisory Committee on Immunization, "Recommendations on the use of COVID-19 vaccines," 22 October 2021. [Online]. Available: https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/recommendations-use-covid-19-vaccines.html. [Accessed 10 December 2021].

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Footnote 3

COVID-19 Evidence Network to Support Decision-Making in Canada (COVID-END), "COVID-19 Living Evidence Synthesis #6: What is the efficacy and effectiveness of available COVID-19 vaccines for variants of concern?," 17 November 2021. [Online]. Available: https://www.mcmasterforum.org/docs/default-source/product-documents/living-evidence-syntheses/covid-19-living-evidence-synthesis-6.24---what-is-the-efficacy-and-effectiveness-of-available-covid-19-vaccines-in-general-and-specifically-for-variants-of-concern.pdf?sfvrsn=c055d57a_7. [Accessed 10 December 2021].

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Footnote 4

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Footnote 5

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Footnote 6

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E. Levin et al., "Waning immune humoral response to BNT162b2 COVID-19 vaccine over 6 months," New England Journal of Medicine, vol. 385, no. e84, 2021.

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Footnote 9

A. Richterman, E. Meyerowitz and M. Cevik, "Indirect protection by reducing transmission: Ending the pandemic with SARS-CoV-2 vaccination," Open Forum Infectious diseases, vol. ofab259, 2021.

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Footnote 10

M. Tenforde et al., "Effectiveness of SARS-CoV-2 mRNA vaccines for preventing COVID-19 hospitalizations in the United States," medRxiv, 2021.

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Footnote 11

P. Christensen et al., "Delta variants of SARS-CoV-2 causes significantly increased vaccine breakthrough COVID-19 cases in Houston, Texas," The American Journal of Pathology, 2021.

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Footnote 12

J. Scott, A. Richterman and M. Cevik, "COVID-19 vaccination: Evidence of waning immunity is overstated," BMJ, vol. 374, no. n2330, 2021.

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Footnote 13

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Footnote 14

Respiratory Virus Infections Working Group, "The Canadian Public Health Laboratory Network protocol for microbiological investigations of emerging respiratory pathogens, including severe acute respiratory infections," Can Commun Dis Rep, vol. 46, no. 6, pp. 205-209, 2020.

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Footnote 15

J. Deeks et al., "Diagnosis of SARS‐CoV‐2 infection and COVID‐19: accuracy of signs and symptoms; molecular, antigen, and antibody tests; and routine laboratory markers," Cochrane Database of Systematic Reviews, vol. 4, 2020.

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Footnote 16

COVID-19 Testing and Screening Expert Advisory Panel, "Priority strategies to optimize testing and screening for COVID-19 in Canada: Report," Health Canada, January 2021. [Online]. Available: https://www.canada.ca/en/health-canada/services/drugs-health-products/covid19-industry/medical-devices/testing-screening-advisory-panel/reports-summaries/priority-strategies.html. [Accessed 10 December 2021].

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Footnote 17

Y. J. Kang, "South Korea's COVID-19 Infection Status: From the perspective of re-positive test results after viral clearance evidenced by negative test results," Diaster Medicine and Public Health Preparedness, pp. 1-2, 2020.

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Footnote 18

A. T. Hanrath, B. A. Payne and C. Duncan, "Prior SARS-CoV-2 infection is associated with protection against symptomatic reinfection," Journal of Infection, vol. 82, no. 4, pp. e29-30, 2021.

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Footnote 19

J. Townsend et al., "The durability of immunity against reinfection by SARS-CoV-2: A comparative evolutionary study," The Lancet Microbe, vol. 2, no. 12, pp. e666-e675, 2021.

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Footnote 20

X. Jiang et al., "Lasting antibody and T cell responses to SARS-CoV-2 in COVID-19 parients three months after infection," Nature Communications, vol. 12, no. 1, p. 897, 2021.

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Footnote 21

L. Yao et al., "Persistance of antibody and cellular immune responses in coronavirus disease 2018 patients over nine months after infection," Journal of Infectious Diseases, vol. 224, no. 4, pp. 586-594, 2021.

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Footnote 22

Government of Canada, "COVID-19 daily epidemiology update," 10 December 2021. [Online]. Available: https://health-infobase.canada.ca/covid-19/epidemiological-summary-covid-19-cases.html. [Accessed 10 December 2021].

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Footnote 23

V. Mathai, A. Das, J. A. Bailey and K. Breuer, "Airflows inside passenger cars and implications for airborne disease transmission," Sciences Advances, vol. 7, no. 1, 2021.

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Footnote 24

C. Juneau, A. Briand, T. Pueyo, P. Collazzo and L. Potvin, "Effective contact tracing for COVID-19: A systematic review," PrePrint: medRXiv, 2020.

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Footnote 25

World Health Organization, "Contact tracing in the context of COVID-19," February 2021. [Online]. Available: https://www.who.int/publications/i/item/contact-tracing-in-the-context-of-covid-19. [Accessed 10 December 2021].

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Footnote 26

National Advisory Committee on Immunization, "NACI Rapid Response: Additional dose of COVID-19 vaccine in immunocompromised individuals followin 1- or 2-dose primary series," September 2021. [Online]. Available: https://www.canada.ca/en/public-health/services/immunization/national-advisory-committee-on-immunization-naci/statement-september-10-2021-additional-dose-covid-19-vaccine-immunocompromised-following-1-2-dose-series.html#fn9. [Accessed 10 December 2021].

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Footnote 27

N. Jones, T. R. Qureshi, J. Larwood, T. Greenhalgh and L. Bourouiba, "Two metres or one: What is the evidence for physical distancing in COVID-19?," BMJ, vol. 370, p. m3223, 2020.

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Footnote 28

H. Wahba, "The antipryetic effect of ibuprofen and acetaminophen in children," Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy, vol. 24, no. 2, pp. 280-284, 2004.

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Footnote 29

A. Otten and L. Waddel, "Evidence brief of COVID-19 quarantine length and reduction strategies and effectiveness, Update 1," Public Health Agency of Canada, December 2020. [Online]. Available: https://cancovid.ca/resources/phac-esg/. [Accessed 10 December 2021].

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Footnote 30

European Centre for Disease Prevention and Control, "Contact tracing for COVID-19: Current evidence, options for scale-up and an assessment of resources needed," May 2020. [Online]. Available: https://www.ecdc.europa.eu/en/publications-data/contact-tracing-covid-19-evidence-scale-up-assessment-resources. [Accessed 10 December 2021].

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Footnote 31

A. Ferreira, T. Young, C. Methews, M. Zunza and N. Low, "Strategies for parnter notification for sexually transmitted infections, including HIV," Cochrane Database of Systematic Reviews, vol. 10, p. CD002843, 2013.

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Footnote 32

Q. Bi et al., "Epidemiology and transmission of COVID-19 in 391 cases and 1286 of their close contacts in Shenzhen, China: A retrospective cohort study," The Landect Infectious Diseases, vol. 20, no. 8, pp. 911-919, 2020.

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Footnote 33

A. Endo, S. Abbot, A. Kucharski and S. Funk, "Estimating the overdispersion in COVID-19 transmission using outbreak sizes outside China," Wellcome open research, vol. 6, no. 67, 2020.

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Footnote 34

W. Bradshaw, E. Alley, J. Huggins, A. Lloyd and K. Esvelt, "Bidirectional contact tracing could dramatically improve COVID-19 control," Nature Communications, vol. 12, p. 232, 2021.

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Footnote 35

J. Raymenants, C. Geenen, M. Neilissen, S. Gorissen and E. Andre, "Empirical evidence on the efficiency of bidirectional contact tracing in COVID-19," Research Square [Preprint], vol. 1, 2021.

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Footnote 36

A. Endo et al., "Implication of backward contact tracing in the presence of overdispersed transmission in COVID-19 outbreaks [Version 3]," Wellcome Open Research, vol. 5, p. 239, 2021.

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Footnote 37

S. Kojaku, L. Hebert-Dufresne, E. Mones, S. Lehmann and Y. Ahn, "The effectiveness of backward contact tracing in networks," Nature Physics, vol. 17, pp. 652-658, 2021.

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Footnote 38

H. Choi, W. Cho, M. Kim and J. Hur, "Public health emergency and crisis management: Case study of SARS-CoV-2 outbreak," International Journal of Environmental Research and Public Health, vol. 17, no. 11, p. 3984, 2020.

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Footnote 39

V. Lee, C. Chiew and W. Khong, "Interrupting transmission of COVID-19: Lessons from containment efforts in Singapore," Journal of Travel Medicine, vol. 27, no. 3, p. taaa039, 2020.

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Footnote 40

Harvard T.H. Chan School of Public Health, "Assessment of risks of SARS-CoV-2 transmission during air travel and non-pharmaceutical interventions to reduce risk," 2020. [Online]. Available: https://cdn1.sph.harvard.edu/wp-content/uploads/sites/2443/2020/10/HSPH-APHI-Phase-I-Report.pdf. [Accessed 10 December 2021].

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Footnote 41

Y. Y. Li, J. X. Wang and X. Chen, "Can a toilet promote virus transmission? From a fluid dynamics perspective," Physics of Fluids, vol. 32, no. 6, 2020.

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Footnote 42

N. Leigh-Hunt et al., "An overview of systematic reviews on the public health consequences of social isolation and loneliness," Public Health, vol. 152, pp. 157-171, 2017.

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Footnote 43

J. Tang, N. Galbraith and J. Truong, "Insights on Canadian Society: Living Alone in Canada," Statistics Canada, 6 March 2019. [Online]. Available: https://publications.gc.ca/collections/collection_2019/statcan/75-006-x/75-006-2019-3-eng.pdf. [Accessed 10 December 2021].

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Footnote 44

A. Thompson, Y. Anisimowicz, B. Miedema, W. Hogg, W. Wodchis and K. Aubrey-Bassler, "The influence of gender and other patient characteristics on healthcare-seeking behaviour: a QUALICOPC study," BMC Family Practice, vol. 7, no. 38, 2016.

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Footnote 45

U.S. Centres for Disease Control, "Public Health Guidance for Community-Related Exposure," 1 March 2021. [Online]. Available: https://www.cdc.gov/coronavirus/2019-ncov/php/public-health-recommendations.html. [Accessed 10 December 2021].

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Footnote 46

World Health Organization, "Public health surveillance for COVID-19: Interim guidance," 16 December 2020. [Online]. Available: https://www.who.int/publications/i/item/who-2019-nCoV-surveillanceguidance-2020.7. [Accessed 10 December 2021].

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