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

Updated April 22, 2021

Note

This page is continually under review and will be updated as this situation evolves. Please visit the provincial and territorial resources for COVID-19 page for updated guidance specific to your province or territory.

On this page

• Case management
• Contact management
  • Table 1: Contact management recommendations by exposure risk level
• Appendix 1: Recommendations for isolation of COVID-19 cases in the community
• Appendix 2: Assessment of a suitable isolation location for a case of COVID-19
• Appendix 3: Recommended infection prevention and control precautions when caring for a case in the home or co-living setting
• Acknowledgments
• Footnotes
• References

The Public Health Agency of Canada (PHAC), in collaboration 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 COVID-19 (i.e., "cases") and contacts of COVID-19 cases within their jurisdictions.

The strategy outlined in this guidance focuses on case and contact management to mitigate the health impacts of COVID-19 on individuals in Canada ^{Reference 1}. 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.

The COVID-19 pandemic has evolved in different ways across Canada. Provincial and territorial (PT) PHAs continue to adjust restrictive community-based measures (CBMs) based on the epidemiology of COVID-19 in their jurisdictions, taking into consideration other important indicators, such as the capacity of their health systems. Increases in COVID-19 cases, hospitalizations and deaths can challenge capacity in the public health and health care systems, requiring adjustments to public health measures (PHMs) in the impacted areas.

SARS-CoV-2, the virus that causes COVID-19, will naturally develop mutations, which are changes to the genetic material in the virus over time. When there have been several significant mutations to the virus, it becomes a variant.

A variant of concern (VOC) is identified when it increases disease spread or disease severity; becomes undetectable by tests; or limits the effectiveness of vaccines or treatments. SARS-CoV-2 VOCs have emerged globally and several of these variants have been identified in Canada, including B.1.1.7, which originated in the UK. Studies have shown that currently circulating VOCs, including B.1.1.7, are more easily transmissible; and there is evidence that B.1.1.7 has a higher case fatality rate than earlier variants circulating in Canada^{Reference 2}. These VOCs have resulted in surges in COVID-19 cases in other countries (e.g., the UK, Ireland, Denmark), which underscores the need for increased emphasis and adherence with established PHMs, applied in a layered approach to reduce transmission of the virus.

This guidance is subject to change as new information on 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 co-ordination 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 should 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. At the time of publication, a process for national reporting of VOCs has been approved, and provinces and territories are working closely with PHAC to implement and optimize this process to ensure national surveillance of VOCs.

In some instances, cases or contacts of cases 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) 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. When deemed useful, PTs should be screening for mutations, and at least a subset (if not all) of those that test positive may be further sequenced (with partial or whole genome) to identify the variant. Screening results can be available sooner than sequencing of virus samples, therefore these efforts may be useful for informing timely public health action.

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 ^{Reference 3Reference 4}.

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^{Reference 5}. 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 where an outbreak is occurring)^{Reference 6}. Interim guidance is available for use of the nucleic acid- and antigen-based rapid detection tests.

There is evidence that, although uncommon, individuals can become re-infected with SARS-CoV-2^{Reference 7}. 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^{Reference 8}. 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. Refer to relevant guidance on clinical management of patients with COVID-19.

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 ^{Reference 9}.

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. 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 their PHA, the case could also isolate in an alternate dwelling such as a hotel or self-containing unit (see Appendix 2). They should isolate for a minimum of 10 days from the onset of symptoms for a symptomatic case, or from the collection date of a positive specimen for an asymptomatic case who remained asymptomatic.

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

• Avoid interactions or sharing spaces (e.g., the same room) with others, if possible;
• Not go out unless required or directed to seek medical care;
• Not go to school, work, or other public places; and
• Not take public transportation to seek medical care, if possible.

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.

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:

• Call ahead to inform the hospital or clinic that the individual has COVID-19, and follow any directions provided;
• When traveling in a private vehicle:
  • minimize occupants in the vehicle (e.g., only the driver and case, if possible)
  • maximize distance between all occupants in the vehicle (e.g., case in the back seat, opposite to the driver in the car; or third row in larger vehicles)
  • open all windows if possible and safe to do so^{Reference 10}
  • the case should be wearing a medical mask ^{Footnote a}, if no contraindications to doing so
  • all other occupants in the vehicle should wear medical masks ^{Footnote a}
• The case and those assisting with transport should follow strict adherence to personal preventive practices to help reduce risk of transmission (e.g., frequent hand hygiene, respiratory etiquette).

Isolating in the community

When isolating 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. The case should:

• be isolated in a separate room with a private washroom where possible (cases in co-living settings may be cohorted in a common space);
• remain in the dedicated space as much as possible;
• avoid interactions with other members of the household or co-living setting;
• wear a medical mask ^{Footnote a} when in a shared space, regardless if others are present; and
• follow recommended personal preventive practices that will help reduce the risk of transmission.

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. When feasible and as directed by the PHA, an alternate dwelling (e.g., hotel, self-containing unit) may be used for isolation of a case.

Factors to consider when determining the suitability of an isolation location in the community (i.e., home, co-living setting), include the following:

• Can the case's clinical condition be managed as an outpatient?
• Is the case able to manage their own care?
• Does the case require care? Is someone available to provide the care?
• What are the characteristics of the home or co-living configuration?
• Are there others with greater risk of more severe disease or outcomes in the home or co-living setting?
• Is the home or co-living setting suitable for isolation?
• Can the case access adequate supplies and necessities?

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

PHAs should 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 based on the history of forced removals. There is also the potential for new trauma if their ability to 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

Ideally, PHAs should provide or facilitate active daily monitoring of cases of COVID-19, including those infected with a VOC, as long as feasible based on available resources. If there are insufficient resources available to provide daily monitoring for all cases, PHAs should give consideration to prioritizing daily monitoring for cases infected with a VOC.

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

• Appropriate adherence to isolation measures in the home or co-living setting;
• Appropriate information on infection prevention and control precautions, personal preventive practices, and environmental cleaning;
• Advice for self-monitoring for symptoms, including daily temperature checks;
• Steps to take if symptoms worsen, including instruction on self-care and how/when to access medical care; and
• When and where to access further diagnostic testing for COVID-19, if appropriate based on provincial/territorial testing strategies;
• Monitoring for symptom-onset in household contacts (if relevant) and/or identifying additional contacts.

PHAs should give consideration to providing additional information about VOCs 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)^{Footnote b}. Criteria may include:

• For symptomatic cases:
  • At least 10 days have passed since onset of first symptom.
  • The case is afebrile and has improved clinically.
    • Absence of anosmia or fatigue/tiredness should not be required.
    • Absence of cough should also not be required for those known to have chronic cough or for those who are experiencing reactive airways post infection.
• For asymptomatic cases:
  • At least 10 days have passed since the date their positive specimen was collected and the case remained asymptomatic.

In general, repeat laboratory testing (e.g., a negative test result) as the basis for discontinuing home isolation is not recommended. 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. In some cases, clinical management may continue to be required after discontinuation of isolation.

Contact management

All recommendations for contacts of COVID-19 cases apply regardless of vaccination status or vaccine rollout progress. Recommendations will be updated as needed based on new evidence regarding vaccine effectiveness and coverage in Canada, including whether vaccines are capable of preventing infection and/or transmission among those immunized, as well as new information regarding vaccine effectiveness against VOCs.

It is important to identify and manage the contacts of cases of COVID-19 to reduce ongoing transmission of the virus in the community^{Reference 11}. Several objectives may be achieved through contact management activities by PHAs, including:

• To facilitate rapid identification of secondary cases of COVID-19 (or source cases, in the context of backward contact tracing);
• To facilitate early implementation of public health measures as appropriate, depending on the contacts' exposure risks; and
• To gain a better understanding of the epidemiology of COVID-19.

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 the coronavirus.

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 (i.e., 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 individual risk assessments 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.

Forward (traditional) contact tracing

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

An individual risk assessment conducted by the PHA can help identify each contact's exposure risk level, determine the required parameters of quarantine or self-monitoring, and PHA actions for the 14-day 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. For example, these factors could include whether the contact has been partially or fully vaccinated, if the contact is immune compromised, the time since last dose of vaccine or the potential risk of transmission to others, especially unvaccinated individuals who are at risk of more severe disease or outcomes from COVID-19. In addition, if there is significant spread of VOCs within the community or there is uncertainty about the individual 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:

• Identifying people who were exposed to a symptomatic case in the period starting 48 hours prior to the case developing a symptom consistent with COVID-19, and until the case was no longer considered infectious (e.g., 10 days following symptom onset for a non-hospitalized case).
• Identifying people who were exposed to a laboratory confirmed asymptomatic case in the period starting 48 hours prior to the day their positive specimen was collected, and until the case was no longer considered infectious (e.g., 10 days after specimen collection date) ^{Reference 12}.

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), and given that in some instances the infectious period of a COVID-19 case may be longer than 48 hours, jurisdictions may extend contact tracing greater than 48 hours when public health capacity and/or the individual 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 advice provided to contacts, based on comprehensive individual risk assessments conducted by PHAs.

Table 1: Contact management recommendations by exposure risk level

Note: All potential exposures described below are considered to have occurred when the case was communicable in determining exposure risk level.
Risk Level	Description	Recommendations for the contact
High risk exposure (close contact)	HCW 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.Footnote c Anyone who 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 has shared an indoor space (e.g., same room) with a case for a prolonged period of time,Footnote d including closed spaces and crowded places, (e.g., social gatherings, workplaces, etc.), without adhering to appropriate individual-level and setting-specific risk mitigation measures. Footnote e Anyone 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), without adhering to appropriate individual-level and setting-specific risk mitigation measures.Footnote e	Quarantine at home for 14 days from last exposureFootnote f. Follow recommended personal preventive practices. If living with the case, avoid further exposure to the case and wear medical mask or a well-constructed and well-fitting, non-medical mask Footnote f when in a shared space (e.g., same room) with the case. Follow PHA directions related to testing requirementsFootnote g. Self-monitor for the appearance of symptoms consistent with COVID-19 for 14 days following their last exposure to the case. 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 PHAReference 13. If symptoms occur, isolate away from others within the home or co-living setting as quickly as possible; put on a medical maskFootnote a 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. Avoid in-person interactions with others, especially those who are at risk for developing more severe disease or outcomes from COVID-19. Contacts who are at risk for developing more severe disease or outcomes should not provide care for the case and should stay elsewhere if feasible.
Low risk exposure	HCW 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. Footnote c Anyone 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.Footnote e Anyone 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. Footnote e	Self-monitor for symptoms for 14 days following their last exposure. If symptoms occur, isolate away from others as quickly as possible, put on a medical maskFootnote a, 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. 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)Footnote c. Follow PHA directions related to testing requirements. Follow recommended personal preventive practices.
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 the individual risk assessment, PHAs may consider more robust approaches to contact management and quarantine specifications, particularly in the context of outbreak investigations involving VOCs. PHAs may also need to consider modifications to quarantine recommendations in exceptional 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^{Reference 14}.

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:

• If laboratory testing is conducted and the test result is negative for SARS-CoV-2, consider continuing to manage the individual as a contact for the duration of the possible 14-day incubation period, based on an individual risk assessment. The contact may be considered for re-testing if they have a worsening or progression of symptoms, and management would depend on the results of the second test.
• If laboratory testing is not conducted, the contact who develops symptoms should be managed as a probable/suspect case as applicable, and they should complete at least 10 days of isolation. Since they are still a contact of a case and not a laboratory confirmed case themselves, depending on the timing of symptom onset and last exposure to a case, this individual may need to quarantine after the isolation period, for 14 days from the last known exposure. In this situation, the PHA should complete an individual risk assessment to determine the appropriate quarantine period based on the individual's level of risk (see Table 1).

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 ^{Reference 15}. These may include the following:

• Using well-trained non-public health staff and volunteers for certain contact tracing activities;
• Repurposing existing resources, such as call centres or hotlines;
• Reducing the intensity of follow-up of contacts based on risk assessment, for example, automated calls or text messages to low-risk contacts, or follow-up text messages instead of daily calls; and
• Leveraging available technology, such as contact tracing software, as well as web-based and mobile phone applications (e.g., COVID Alert).

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.)^{Reference 16}.

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)^{Reference 17}.

Backward contact tracing

In addition to traditional (forward) contact tracing, PHAs may 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. 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 there is high individual-level variation in the distribution of the number of secondary transmissions. Clusters associated with these cases have been referred to as super-spreading events (SSEs).

Mutations in the genetic code of SARS-CoV-2 can also cause the virus to act in ways that have significant impacts on case and contact management (e.g., increases in disease spread 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:

• Identify the source case;
• Find additional cases by focusing on the setting where a case's exposure likely took place; and
• Interrupt additional chains of transmission by then employing traditional (forward) contact tracing for the newly identified cases.

If the source case is identified through backward contact tracing, traditional (forward) contact tracing should be employed as detailed above, and contacts managed based on their risk of exposure as described in Table 1. As in the case of forward contact tracing, 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. Backward contact tracing may also be less useful during periods of restrictive public health measures, due to fewer events or localized settings where outbreaks or SSEs might occur ^{Reference 18}. 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 currently limited evidence regarding the effectiveness of backward tracing for COVID-19, so it is not possible to be definitive about when it would be most useful or how it would be best implemented. A limited number of countries have utilized this strategy, and beneficial impact was correlated with low incidence and limited community transmission ^{Reference 19Reference 20}.

Provinces/territories (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

As of March 25, 2020, all travellers entering Canada must follow the rules set out by the emergency orders under the Quarantine Act. There are some exemptions to these border restrictions and mandatory quarantine requirements for which individuals or groups can apply.

Unless exempted, all incoming travellers/citizens are required to quarantine (if they are not experiencing symptoms of COVID-19) or isolate (if experiencing symptoms of COVID-19) as directed, for 14 days following their arrival to Canada. Quarantine and isolation instructions for returning travellers are available on the Mandatory quarantine or isolation web page.

International travellers may have to undergo other types of border measures, such as COVID-19 testing. For further information, refer to the Government of Canada's Travel Webpage.

History of travel should be considered by PHAs during the individual risk assessment during contact tracing. Potential travel-related exposures on specific conveyances (e.g., flights, trains, cruise ships) may be available.

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 mandatory use of masks, physical distancing, reduced occupancy, environmental cleaning, and hand hygiene, applied in a layered approach, can significantly reduce the likelihood of transmission^{Reference 21}.

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:

• Type, severity, and onset date of symptoms for symptomatic cases, or specimen collection date for asymptomatic cases, in relation to the flight date;
• Current messaging to all international travellers, specifically that they must enter into a legally mandated14 day quarantine period starting the day they enter Canada;
• Current legislation, regulations and policies that may be imposed on domestic travellers by a PT upon arrival to that PT (e.g., that a domestic traveller must enter into a legally mandated 14 day quarantine period starting the day they enter a PT);
• Timing of notification and likelihood of getting sufficient passenger contact information (e.g., within 14 days of flight); and
• Incremental benefit of individual communication to those seated within 2 metres (or more)^{Footnote h} of the case versus public communication of the flight number.

If the province/territory determines that notification to potential contacts is required, the PHA can follow local protocols for publicly communicating when a case has had a history of travel during their period of communicability. The information required is the flight number, flight date, departure/arrival locations, and affected rows of the flight. Additionally, flight exposure notifications received by PHAC's Inter-jurisdictional Notices (IJN) team can be posted on the Coronavirus disease (COVID-19): Locations where you may have been exposed to COVID-19 webpage.

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:

• Avoid in-person interactions with others, including members of their household, if possible;
• Not go out unless required or directed to seek medical care;
  • If a case must go out to seek medical care, they should wear a medical mask ^{Footnote a}.
• Not go to school, work, or other public places; and
• Not take public transportation to seek medical care, if possible.

Isolating in the community

When isolating at home or co-living setting, it is important that the risk of transmission, through direct or indirect contact, to other members of the household or 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:

• A case should have their own room and a dedicated washroom.
  • When awake, the case should wear a medical mask^{Footnote a}, when they are in a shared space (e.g., kitchen, washroom, hallway), regardless if other household members or occupants in the co-living setting are present, to avoid aerosol transmission and/or contaminating shared surfaces and objects.
• The case and other members of the household or co-living setting should avoid any activities that put them in a shared space (e.g., in the same room) with one another. This includes avoiding shared activities like watching television, congregate dining (e.g., family meals), playing games, etc.
• When other members of the household or co-living setting are unable to avoid sharing a space (e.g., the same room) with the case, they should wear a medical mask or a properly worn, well-constructed and well-fitting non-medical mask^{Footnote f}. If household members are at high risk of more severe disease or outcomes, a medical mask should be worn^{Footnote a}.
• If a member of the household or co-living setting needs to provide care to the case, they should wear a medical mask^{Footnote a}. The case should only access an outdoor setting if it is a private space (i.e., their private backyard or balcony). If household members are present in this outdoor space, all individuals present should continue to wear masks and practice physical distancing.
• The case should avoid sharing personal items with others, as much as possible (e.g., towels, bed linen, cigarettes, unwashed eating utensils, toothbrushes, etc.).
• In situations where childcare is shared between two homes, wherever possible consider having the child stay in one home for the duration of the isolation or quarantine period.
• If possible, shared spaces (e.g., kitchen, washroom, hallways) should be well ventilated (e.g., windows open, as weather permits), regardless if individuals are present or not.
• The case and all household members or occupants of the co-living setting should strictly follow the recommended personal preventive practices.
• A list of supplies to have on-hand while isolating is available.

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:

• In overcrowded housing, or where a dedicated room and washroom are not available for isolation, consider having the case, household members, or other occupants relocate to another location so the case can be isolated.
• Take steps to bring fresh air into the space, by opening windows and doors to the outside if possible (e.g., depending on weather) and safe (e.g., no fall hazards, outdoor air quality); and ensuring the mechanical ventilation system (e.g., heating, ventilation and air conditioning (HVAC) system) is functioning properly and turned on continuously if possible.
• Although the effectiveness is limited due to possible transmission of SARS-CoV-2 via respiratory droplets and aerosols, consideration may be given to separating the case from others with dividers such as curtains in a shared space (e.g., home with limited rooms, sharing space for sleeping).
  • If other members of the home or co-living setting are sleeping in the same room as a case, it is important to maintain as much distance as possible from the case (ideally a minimum of 2 metres)^{Footnote i}. This may be accomplished by separating beds and having occupants sleep head-to-toe.
• If a separate washroom is not available, open the window, turn on the exhaust fan to improve ventilation, put the lid of the toilet down before flushing and, when possible, clean and disinfect surfaces touched by the case after each use^{Reference 22}.

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 public health authority (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., 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?

Symptomatic and asymptomatic 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 wear a medical mask^{Footnote a}; maintain appropriate personal preventive practices (e.g., maintain proper hygiene practices, clean and disinfect high-touch surfaces, etc.), and isolate away from others.

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

• Social and economic circumstances, such as lost income or poverty (e.g., unable to purchase necessary supplies, housing instability, etc.), unstable employment, inflexible working conditions, food insecurity, and domestic violence or abuse;
• Individual skills, abilities and vulnerabilities, such as difficulty reading, speaking, understanding or communicating; physical or psychological difficulty undertaking personal preventive practices; need for assistance with personal or medical care activities or supplies; or need for ongoing supervision. COVID-19 guidance on considerations for people with disabilities in Canada is available.
• Social or geographic isolation such as lacking family, friends, or community resources for support^{Reference 23}, or residing in an area with reduced access to services or supports; including mental health and addiction support, as well as telecommunications access.
• The ability for the case to access plain-language instructions in the appropriate languages related to proper personal hygiene practices, isolating away from others, self-monitoring for symptoms, and when to seek help. Note that male cases are more likely to live alone and may be less likely to seek help^{Reference 24Reference 25}.

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:

• The caregiver should be willing and able to provide the necessary care and monitoring for the case.
• If possible, the caregiver should not be a person who is at risk for more severe disease or outcomes.
• The caregiver should reduce their risk of COVID-19 infection by wearing a medical mask^{Footnote a} when providing care to the case. They should also use appropriate eye protection while providing care to the case (see Appendix 3).
• Advice is available to support those caring for someone with COVID-19 at home:
  • How to care for a child with COVID-19 at home: Advice for caregivers
  • How to care for someone with COVID-19 at home
  • How to care for a person with COVID-19 at home: Advice for caregivers

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, which may require relocating the case, their roommates, or other household members to another location, (e.g., hotel, self-containing unit), if possible and as directed by the PHA. Relocation will be dependent on a variety of factors, including guidance from the jurisdictions PT 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, or to relocate the case, 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. Specific guidance has been developed on the considerations for people experiencing homelessness and for post-secondary institutions.

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 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 a location determined by public health, such as a designated hotel.

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

The PHA should determine if the home or co-living setting is suitable for isolation of the case. Cases may live in conditions 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 or not 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 usually taken, 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, PHAs should 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 medical mask^{Footnote a}, as well as 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:

• How to care for a child with COVID-19 at home: Advice for caregivers
• How to care for someone with COVID-19 at home
• How to care for a person with COVID-19 at home: Advice for caregivers

Additional information may be provided to caregivers in the home related to how to appropriately put on (don) and take off (doff) eye protection and gloves.

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.

• Eye protection should be worn over prescription eyeglasses. Prescription eyeglasses alone are not adequate protection against respiratory droplets.
• Protective eye wear should be put on after putting on a mask.
• If using gloves, they should be donned (see below) after applying eye protection.
• To remove eye protection, first remove gloves and perform hand hygiene. Then remove the eye protection by handling the arms of goggles or sides or back of face shield. The front of the goggles or face shield is considered contaminated.
• Discard the eye protection into a plastic lined waste container. If the eye protection is not intended for single use, clean it with soap and water and then disinfect it with approved hard-surface disinfectants or, if not available, a diluted bleach solution, being mindful not to contaminate the environment with the eye protection. Refer to Clean and disinfect all high-touch surfaces for instructions on diluting bleach.
• Perform hand hygiene.

Gloves

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

However, 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.

• Gloves should be removed, hand hygiene performed, and new gloves applied when they become soiled or torn during care.
• To remove gloves safely, with one of your gloved hands pull off your glove for the opposite hand from the fingertips, as you are pulling, form your glove into a ball within the palm of your gloved hand. To remove your other glove, slide your ungloved hand in under the glove at the wrist and gently roll inside out, and away from your body. Avoid touching the outside of the gloves with your bare hands.
• Discard the gloves in a plastic-lined waste container.
• Perform hand hygiene.
• Double-gloving is not necessary.

Acknowledgments

The Public Health Measures (PHM) technical guidance is developed and approved in collaboration with federal, provincial and territorial partners, via the Technical Advisory Committee (TAC) and/or the Special Advisory Committee (SAC). In its guidance development process, PHM also works closely with: multilateral partners; other government departments; First Nations, Inuit and Métis stakeholders (through the Public Health Working Group on Remote and Isolated Communities); Sex and Gender-based Analysis (SGBA) experts at Public Health Agency of Canada; and other external stakeholders with a vested interest or a stake in the guidance.

This current iteration was prepared by: Jill Williams, Lynn Cochrane, Nicole Winters, Corey Green and Lisa Paddle

Previous iterations prepared by: Jill Sciberras, Jill Williams, Lynn Cochrane, Corey Green, Sharon E. Smith, Angela Sinilaite, Alexandra Nunn, Fanie Lalonde and Lisa Paddle

and supported by: Canadian Pandemic Influenza Preparedness (CPIP) Task Group Members, an external expert group: Bonnie Henry, Susy Hota, Brian Schwartz, Carolina Alfieri, Ian Gemmill, Kim Daly (ISC), Todd Hatchette, Erin Henry, Nadine Sicard, Michelle Murti and Eleni Galanis