Mpox: Public health management of human cases and associated human contacts in Canada

February 24, 2025

Summary of updates

February 24, 2025, update

Updates have been made to the last version (August 23, 2024) to:

• provide updated references for the modes of transmission of mpox virus (MPXV) based on emerging evidence
• further emphasize language around non-sexual modes of transmission given recent global epidemiology indicating increased cases within household contacts (for example, children)
• include high-level information regarding the most recent public health risk assessment on clade Ia and Ib MPXV multi-country outbreaks  

August 23, 2024, update

Updates have been made to the last version (January 4, 2024) to:

• provide more information on clade I and the potential risk of importation into Canada
• include the most recent National Advisory Committee on Immunization (NACI) guidance on the use of Imvamune^® in the context of a routine immunization program
• remove all references of "monkeypox" terminology, as it has been more than 1 year since the World Health Organization (WHO) recommended the disease name be changed to "mpox"
• updated literature references based on evolving evidence

January 4, 2024, update

Updates have been made to the previous version (February 23, 2023) to:

• acknowledge the risk of pre-symptomatic transmission of mpox
• provide public health authorities (PHAs) with advice for contact tracing for those exposed to a case in the pre-symptomatic period and
• include the latest information on mpox vaccination

February 23, 2023, update

An update was made to the previous version (October 18, 2022) of this document to change the term "monkeypox" disease to "mpox" disease. This change aligns with the WHO's preferred nomenclature for the disease. The WHO recommended this change in November 2022 to help reduce stigma and other concerns associated with the previous terminology.

When referring to the virus itself, "monkeypox virus" (abbreviated to "MPXV") will be used throughout this guidance to align with the International Committee on Taxonomy of Viruses' (ICTV) terminology. The Public Health Agency of Canada (PHAC) will continue to monitor any changes to ICTV terminology and update guidance as needed.

October 18, 2022, update

Updates have been made to the previous version (June 21, 2022). They include the following changes:

• identify populations who may be at greater risk of infection during the current outbreak, while recognizing that risk of exposure to mpox is not exclusive to any group or setting
• clarify advice for condom use following mpox infection
  • Note that PHAs may consider developing targeted messaging for gatherings/settings where close physical contact, including sexual activity, may take place (for example, parties, clubs, raves, festivals)
• provide more information related to animals that have been exposed to a human case of mpox, including risk mitigation measures that may be put in place
• provide information on safer sex practices in the context of the mpox outbreak

On this page

• Introduction
• Background
• Public health management of cases
• Public health management of contacts
• Additional resources
• Footnotes
• References

Introduction

PHAC, in collaboration with provincial/territorial (PT) PHAs and other relevant federal government departments, has developed this document. It provides guidance to PHAs working at the federal/provincial/territorial (FPT) level in the event cases of mpox are suspected or confirmed within their jurisdictions.

As mpox is not endemic in Canada and the situation continues to evolve, this document also follows a precautionary approach, in order to prevent the long-term establishment of mpox in Canada.

At the time of this update, the majority of cases in Canada are clade II, and most cases are a result of sexual transmission (although other modes of transmission also exist), occurring primarily among gay, bisexual and other men who have sex with men (gbMSM), especially those with multiple sexual partners. However, it is important to stress that the risk of exposure to the MPXV is not exclusive to any group or setting.

The strategy outlined in this guidance relies on case and contact management with the goal of outbreak containment, including among:

• individuals at higher risk of exposure, such as someone who has had close contact with a suspected or confirmed case of mpox (please refer to Table 1: Classification of contacts by human to human exposure risk level for descriptions and examples of contacts)
• settings/events linked to transmission, such as attending:
  • sex-on-premise venues
  • group sex events
  • congregate living settings
• populations with a higher risk of severe disease, such as individuals who are:
  • immunocompromised (including people with advanced or uncontrolled HIV)
  • pregnant
  • young children including infants

To achieve this, the objectives for this guidance include rapidly stopping chains of transmission to reduce the spread of mpox and mitigate the impacts in Canada. This will ultimately contribute to the overall goal of eliminating person-to-person transmission of mpox in Canada.

Guidance on diagnostic laboratory, specimen handling and transportation, clinical care, and infection prevention and control (IPC) measures in other settings (for example, Canadian points of entry, health care settings, long-term care facilities) are beyond the scope of this document. More information on publications that address these topics can be found here: Mpox: Technical documents for laboratory personnel and health professionals.

This guidance is informed by the latest available scientific evidence, national and international epidemiological data and expert opinion. Although a significant volume of scientific literature has been published since the introduction of mpox into Canada, there are still several knowledge gaps on the transmission dynamics of MPXV. PHAC continues to apply an evidence-informed approach to its case and contact management guidance for mpox. We will adjust this document accordingly as new scientific information becomes available.

This guidance should be read in conjunction with relevant FPT and local legislation, guidelines, regulations and policies. It should be adapted to the local context as required.

PHAC has developed this document based on the Canadian situation. Therefore, it may differ from guidance developed by other countries.

Background

MPXV in humans

The agent

MPXV is part of the Poxviridae family. MPXV has two distinct genetic clades: clade I and clade II. Clade I is divided into two sub-clades (Ia and Ib). According to the data from endemic regions, clade Ia is more common among children^{Footnote 1Footnote 2}, and has been reported as having a higher case fatality rate up to 10%^{Footnote 3Footnote 4Footnote 5Footnote 6}. Clade Ib is more common among adults and early evidence suggest it is less severe than clade Ia^{Footnote 7}. The case fatality rate for clade II is approximately 0.1% to 3.6%, with cases occurring outside of endemic regions rarely being fatal^{Footnote 8Footnote 9}.

Presentation in humans

The incubation period for human-to-human transmission is usually 7 to 10 days, but can range from 3 to 21 days^{Footnote 10Footnote 11Footnote 12Footnote 13}.

Mpox presents with either or both:

• systemic symptoms (such as, fever, fatigue, headache, myalgia)
• painful skin or mucosal lesions (for example, in the mouth, throat, genitals and/or rectum) that evolve from flat to raised lesions filled with liquid, then ulcers that scab over.
  • Lesions in the same body area tend to evolve at the same time (synchronously). However, individuals may have an atypical or asynchronous rash.

Asymptomatic mpox infections have been reported in non-endemic countries since the 2022 outbreak; however, it remains unclear how common asymptomatic cases are^{Footnote 14}.

While mpox usually self-resolves in 2 to 4 weeks, severe cases can occur and may be fatal^{Footnote 15}.

Transmission of mpox

MPXV can be spread to humans in 3 ways:

• human to human,
• animal to human,
• through contact with fomites^{Footnote 16Footnote 17Footnote 18Footnote 19Footnote 20Footnote 21Footnote 22Footnote 23Footnote 24}

Mpox can spread from person-to-person through direct contact with lesions or scabs of a person with mpox. These lesions or scabs may be found on the skin or mucosal surfaces, such as:

• genitals
• anus and rectum
• mouth and throat
• eyes

It can spread through contact with bodily fluids of a person with mpox, such as^{Footnote 25Footnote 26}:

• semen^{Footnote 27}
• saliva
• blood

The virus may spread through respiratory particles^{Footnote 28Footnote 29}, such as from:

• coughing or sneezing
• talking or breathing

Although spread through the air is possible, current data continues to support a minimal role of spread through the air for clade I and II MPXV. However, this possibility should continue to be examined given ongoing viral evolution^{Footnote 28}.

It can also spread by coming into direct contact with personal items a person with mpox has used, including:

• towels
• clothing
• bedding
• other shared objects

People with mpox may be contagious up to 4 days before the start of their symptoms, and the lesions remain contagious to the touch until the scabs have fallen and a new layer of skin appears.

For more information on the modes of transmission, clinical manifestations, diagnosis and treatment for mpox, refer to PHAC's Mpox: For health professionals web page. Information on mpox for the general public is also available, including:

• Mpox: How it spreads, prevention and risks
• Mpox: Symptoms, getting tested, what to do if you have mpox or were exposed

Current status

There are two distinct lineages of MPXV: clade I and clade II. Both clades are endemic in Africa.

There continues to be an escalating outbreak of mpox in the Democratic Republic of the Congo associated with clade Ia MPXV. Escalation of this outbreak has been associated with the detection of a novel sub-lineage of clade I (clade Ib). There are increasing reports of confirmed and suspected mpox cases in other African countries, as well as countries outside of Africa. In response to this ongoing upsurge in cases, the WHO announced on August 14, 2024 that mpox constitutes a public health emergency of international concern (PHEIC).

Mpox cases continue to be reported within Canada and around the world, in both endemic and non-endemic countries. The majority of mpox cases reported in Canada continue to be the result of clade IIb MPXV, based on genomic sequencing available to date.

PHAC has conducted multiple rapid risk assessments on MPXV and the public health implications for Canada in order to support health professionals responsible for managing public health risks. Based on the latest risk assessment, following importation of clade Ia or Ib MPXV into Canada, onward transmission is primarily expected in the case’s household and non-household close contacts, including sexual contacts, with the potential for amplification within high-contact sexual networks, including among gbMSM, as well as sex workers and their close contacts, similar to the start of the ongoing clade IIb global mpox outbreak. The overall risk to people living in Canada is low, as transmission of clade Ia or Ib in Canada following importation is expected to be limited, with minor impact on the general population. The probability of importation of clade I MPXV into Canada is expected to increase if global outbreaks continue to spread, especially to countries with higher travel volumes to and from Canada or if clade I MPXV enters high-contact sexual networks. Early detection, diagnosis, isolation, and contact tracing are key for the effective control of local transmission of MPXV in Canada. No fatalities have been reported among mpox cases in Canada to date.  

PHAC continues to work with PTs and international partners to actively monitor the situation. For up-to-date information, refer to PHAC's Mpox: Update web page.

For further details on mpox epidemiology in Canada, refer to PHAC's Mpox epidemiology update web page.

Mpox vaccination

Imvamune^® is a licensed non-replicating third-generation smallpox vaccine. It is indicated for immunization against smallpox, mpox and related Orthopoxvirus infection and disease in adults 18 years of age and older determined to be at high risk for exposure. Vaccination is expected to protect against both clade I and clade II.

In consideration of ongoing local transmission, the need for national guidance on pre-exposure vaccination was noted. In May 2024 the National Advisory Committee on Immunization (NACI) provided interim guidance on the use of Imvamune^® in the context of a routine immunization program.

NACI recommends that individuals at high risk of mpox should receive two doses of Imvamune^® administered at least 28 days (4 weeks) apart.

Individuals considered at high risk of mpox exposure include men who have sex with men who engage in high-risk activities (for example, multiple sexual partners, recent STI).

Regardless of gender or sex assigned at birth, the following populations are also considered at high-risk for mpox, and recommended 2-dose vaccination with Imvamune^®: sexual partners of men who have sex with men engaging in high-risk activities, sex workers, as well as anyone who will be travelling to foreign countries with the intention of engaging in sexual activity in exchange for money (for example, engaging in sex tourism).

NACI continues to recommend the use of Imvamune^® as a post-exposure vaccination (also known and referred to as post-exposure prophylaxis) to individuals who have had high risk exposure(s) to a probable or confirmed case of mpox, or within a setting where transmission is occurring, if they have not received both doses of pre-exposure vaccination.

Proactive communications

PHAs may consider proactive, non-stigmatizing communication and outreach strategies to reach groups that may be at higher risk of exposure based on current epidemiological data. They should do so in collaboration with local community-based stakeholders and organizations.

In particular, PHAs may consider enhancing these types of communications during times where transmission may be expected to increase, such as during periods of increased:

• international travel (for example, spring break, summer vacations, winter holidays), since mpox is still causing active outbreaks in various countries
• mass gatherings, given the higher likelihood of increased sexual activity (such as festivals and other large social or cultural events)

PHAs may also find it beneficial to provide targeted messaging and advice on risk mitigation strategies for settings where activities may increase the risk of mpox transmission, such as sex-on-premise venues and congregate living settings, like group homes, student residences, shelters and correctional facilities. PHAs could also highlight that substance use (drugs and/or alcohol) may also impact individuals' assessment of risk and reduce adherence to safer sex practices^{Footnote 30}.

Information can be found at Mpox (monkeypox): How operators can reduce the risk of spread in community settings.

Public health management of cases

Case definitions and reporting

National case definitions for mpox have been established and are being used in this document. If PHA's suspect a case of mpox, they should follow their provincial, territorial or local reporting requirements. PHAC's mpox case report form is available at the following link: Mpox (monkeypox): For health professionals – Surveillance.

Public health activities for case management

The PHA's activities for case management should proceed as usual, regardless of the MPXV clade the case has been infected with.

At this time, there have been reports of reinfection cases of mpox globally, however, details remain limited^{Footnote 31Footnote 32Footnote 33}. As such, case management activities should also proceed as usual for reinfection cases.

Such activities may include:

• isolating cases until they are deemed no longer contagious by the PHA
  • Individual situations vary and are unique, therefore PHAs may need to modify isolation approaches used for cases. If this approach is taken, PHAs should consider factors that may influence the risk of spread, such as the case's symptoms and their ability to adhere to recommended public health measures (PHMs), as well as risk of exposure and onward transmission to populations at risk of more severe disease (such as individuals that are immunocompromised, individuals that are pregnant, or young children including infants)^{Footnote 6Footnote 15}. Modifications in isolation should be designed to maintain the objectives of this guidance (for example, rapidly stopping chains of transmission to reduce the spread of mpox and mitigate the impacts in Canada).
  • When hospital-level care is not required, cases may isolate at home when feasible, or in an alternate dwelling such as a hotel or self-containing accommodation as directed by the PHA, when necessary.
    • Note: For the remainder of this document, "home" will be used as an all-encompassing term to refer to the case's place of isolation.
• identifying and mitigating any barriers to effective isolation at the home, as well as providing the appropriate health, psychological, material and essential supports needed for adequate living
  • PHAs should take into account the unique characteristics of the case and their living situation (for example, if the case is living in a congregate living setting like a group home, student residence, shelter or correctional facility) and adjust advice accordingly (for example, recommending isolating the case in an alternative setting, when no other option is available).
• active monitoring of mpox cases (such as through regular communication), recognizing that frequency may vary by PHA and the local context
  • Monitoring activities can support learning about the clinical evolution of the infection, address emerging issues and encourage the appropriate isolation compliance, including by connecting the individual to community support as appropriate.
  • Note: More severe disease has historically been observed with clade Ia MPXV infections occurring in some African countries. There are however, many factors that can impact disease severity which may not apply to a Canadian context. When performing active monitoring, PHAs should remain vigilant of the potential for more severe disease in clade I cases and refer them to an HCP as appropriate.
• providing information on PHMs that the case, along with their caregiver and household members, should follow (refer to the section on Public health measures recommendations for suspected, probable and confirmed cases)
• providing general advice on steps to take if signs/symptoms worsen, including instruction on self-care, when to contact their HCP and how/when to access medical care
• identifying all contacts during the case's period of communicability, including persons identified specifically as contacts by the case, and groups of individuals potentially exposed during an event or while at a location, depending on the activities practised while at those sites

Public health measures recommendations for suspected, probable and confirmed cases

When hospital-level care is not required, cases are recommended to isolate while they are contagious. The contagious period is typically from the start of symptoms until the lesions are completely healed (scabs have fallen off and wounds show evidence of epithelialization, such as a light pink/shiny pearl appearance). This typically takes 2 to 4 weeks, but may take longer.

The recommended PHMs should remain consistent, regardless of the MPXV clade the case has been infected with or if the case has previously had an mpox infection. Recommended PHMs are outlined as follows.

General recommendations for isolation

Cases should remain in isolation until deemed no longer contagious.

During the isolation period, cases should stay at home and away from others, and:

• as much as possible, have necessities (for example, medication and groceries) delivered to the home
• not travel to other cities, regions/provinces/territories or to other countries
• postpone elective medical visits and other elective procedures (such as elective dental visits and blood tests)
• not donate blood or any other bodily fluid (including sperm) or tissue
• limit contact with others from outside the home
  • This includes not having visitors inside the home, with the exception of an HCP or other trained professional who follows relevant IPC measures to provide necessary patient care services.

If the case must leave isolation to access urgent medical care, or for other such emergencies, they should:

• alert HCPs of their infection prior to seeking care when possible, so that the HCP can take proper infection control measures
• use private transportation instead of public transportation when possible
• use personal protective measures (this is especially important if the use of public transportation is unavoidable):
  • Wear a well-fitting medical mask
  • Cover all lesions with clothing or bandages
  • Maximize distance from others
  • Practise hand hygiene and respiratory etiquette

Recommendations to reduce the risk of spread to household members

If the case lives with other people, they should isolate in a separate space (such as a private room for sleeping and washroom) whenever possible, especially if they have:

• weeping lesions
• lesions that are hard to cover (such as on the face, neck, hands)
• respiratory symptoms (particularly if they have lesions inside the mouth or throat)

If isolating in a separate space or room from others in the household and use of a separate washroom is not possible, the case should maintain as much distance as possible from others, including during sleep (for example, sleeping in separate beds). Cases should also clean and disinfect all surfaces and objects they have had contact with and immediately remove and launder used items (for example, towels, clothes).

Cases should:

• avoid touching other people directly, including sexual contact, even if they are fully vaccinated against mpox
• not share clothes, bedding, towels, utensils, toothbrushes, razors, sex toys, needles or any other items that may be contaminated with infectious particles from lesions or body fluids
• practise regular hand hygiene and respiratory etiquette
• avoid all contact with populations at risk of more severe disease (for example, individuals who are immunocompromised, individuals who are pregnant, young children including infants)^{Footnote 6Footnote 15}
  • If the case must have close contact with a young child (for example, they provide care to or breastfeed), the PHA or HCP should provide them with personalized advice on preventing onward transmission, given the potential for severe disease in young children.
  • It should be noted that it is not known at this time if MPXV can pass through breast milk.

When sharing a space with others is unavoidable, cases should take the following measures:

• cover all lesions with clothing or bandages as much as possible (including when accessing common spaces, even if others are not present)
• wear a well-fitting medical mask
  • When this is not possible, other people should wear a medical mask when in a shared space with the case.

Recommendations to reduce the risk of spread to animals (pets, livestock and wildlife)

Animals don't currently play a role in the transmission of MPXV in Canada. The current spread of mpox disease in Canada is a result of human-to-human transmission. However, humans can also spread the virus to animals, which could then spread it back to humans.

Many different animal species are susceptible to MPXV, especially rodent species such as squirrels and rats. However, the full range of animals susceptible to MPXV, particularly in North America, remains unknown at this time. One report from France in August 2022 suggests human-to-dog transmission of MPXV following infection in one dog after close contact with human cases in a household. However, there have been no further studies suggestive of human-to-dog transmission reported to date^{Footnote 34}. Consider measures to prevent any possible spread of the virus, to limit risk of creating an animal reservoir for this virus in Canada.

People with mpox should be advised they could possibly spread mpox to animals and to avoid contact with animals, including pets, livestock, and wildlife.

• avoid handling, feeding or working closely with animals
• avoid having animals inside the home where they are isolating
• have another member of their household care for their animals until they are no longer contagious

If this isn't possible, people with mpox should:

• cover all lesions with clothing or bandages and wear a well-fitting medical mask and gloves when near the animals, their food, bedding or other items
• avoid close contact with animals (such as petting, kissing, cuddling, sharing sleeping areas, sharing food)
• practise proper hand hygiene and respiratory etiquette
• clean and disinfect high-touch surfaces frequently
• be advised that if they have had close contact with animals during their contagious period, the animal(s) should be monitored for clinical signs for 21 days after their last exposure and kept away from other animals and people during this time
  • Consult a veterinarian if an animal develops clinical signs of mpox (such as fever, depression, not eating, respiratory signs, diarrhea, oral ulcers, skin lesions) within 21 days of close contact with a case. Be sure to communicate the animal has been exposed to mpox.

Recommendations for environmental hygiene

The risk of fomite transmission of MPXV remains difficult to characterize. In general, orthopoxviruses are known to be very stable in the environment and remain infectious for prolonged periods in scabs, especially in dark and cold environments^{Footnote 35Footnote 36Footnote 37}. Materials contaminated with orthopoxviruses (such as clothes, paper, dust) can remain contagious for months to years if not disinfected^{Footnote 35Footnote 36Footnote 37Footnote 38Footnote 39Footnote 40}.

Some evidence has found persistent MPXV DNA^{Footnote 16Footnote 17Footnote 19Footnote 20Footnote 21Footnote 22Footnote 41}, and in some cases potentially infectious virus^{Footnote 16Footnote 17Footnote 18Footnote 19}, on surfaces and fabrics directly touched by cases. However, many unknown factors remain, including the viral load needed for transmission to occur and the stability of infectious virus on surfaces and fabrics in various environmental conditions. Some small experimental studies have shown that despite environmental stability, poxviruses can be inactivated when exposed to standard chemical disinfectants and temperature greater than 50° Celsius^{Footnote 42Footnote 43Footnote 44Footnote 45Footnote 46}.

In light of this, PHAs should advise cases and/or caregivers on proper environmental hygiene in the home, including recommendations for:

• handling laundry
• cleaning and disinfecting high-touch surfaces and objects
• cleaning and vacuuming furniture and carpets
• handling and cleaning dishware and utensils
• proper waste management in the home
  • For example, contaminated materials should be disposed of in a manner that prevents access by pets or wild animals, rodents in particular.

Detailed advice on environmental hygiene is available for cases and their caregivers on PHAC's website.

Post-recovery risk reduction

MPXV has been found in the body fluids (such as semen) of some cases for several weeks after their recovery^{Footnote aFootnote 56Footnote 57Footnote 27Footnote 58Footnote 59Footnote 60Footnote 61Footnote 62}. However, this has not been definitively linked with mpox spread. At this time, the WHO suggests condom use for cases 12 weeks post-mpox infection^{Footnote 47}.

As such, cases who have recovered (once scabs have fallen off and the wounds are epithelialized) should be advised by the PHA to use barrier protection (such as condoms, dental dams):

• during sexual activity, as it may decrease the possible risk of MPXV transmission through genital fluids and lower their partner's potential chances of being exposed^{Footnote aFootnote 56Footnote 57Footnote 27Footnote 58Footnote 59Footnote 60Footnote 61Footnote 62}
• to further help prevent the spread of other sexually transmitted infections.

For additional information on barrier protection, consult PHAC's Sexually Transmitted and Blood Borne Infections (STBBI) Prevention Guide.

Public health measures for caregivers at the home

Ideally, only one individual in the home should provide direct care to the case, if and when needed (referred to as the "caregiver"). HCPs entering the home to provide medical care should follow appropriate IPC protocols.

The caregiver should not be someone who is at risk of more severe disease from mpox (for example, individuals who are immunocompromised, individuals who are pregnant, young children).

The PHA should provide caregivers with instructions on how to reduce their risk of mpox infection. These may include:

• avoiding close physical contact with the case (even if the caregiver is fully vaccinated)
  • If close contact is unavoidable, the caregiver should wear a well-fitting medical mask and cover any skin that could potentially come in contact with the case (for example, wear long pants, long sleeves, an apron).
    • follow appropriate steps for removing clothing and handling laundry after providing care
  • If direct contact with lesions is unavoidable, the caregiver should also wear disposable gloves.
• practising frequent hand hygiene
• having the case handle their own laundry, utensils and dishware, and be responsible for cleaning and disinfecting in the home
  • The caregiver or household member should follow specific instructions to reduce the risk of infection if this is unavoidable.

Caregivers should self-monitor for signs/symptoms for 21 days since their last exposure to the case (refer to the following section on contact management for further details). If signs/symptoms develop, they should immediately isolate away from others, notify their HCP or local PHA and follow their instructions.

Public health management of contacts

Contact tracing

The purpose of contact tracing is to:

• ensure contacts are aware of:
  • their potential exposure
  • their potential to develop infection even if fully vaccinated
  • expectations of monitoring for any signs/symptoms (including the need to monitor for mild symptoms that can go unnoticed)^{Footnote 48}
  • risk mitigation measures to practise for 21 days post-exposure, depending on the circumstances (for example, ensure contacts are aware of and can evaluate the risks associated with planned activities including sexual activity, travelling or attending social events/gatherings)
  • the importance of consistently practising recommended PHMs, given the potential for pre-symptomatic transmission (details provided in the following section)
  • what to do if they develop mpox symptoms (for example, isolate immediately, advise PHA)
• provide information about post-exposure prophylaxis and refer to their HCP, if eligible, to prevent the onset of disease and stop further transmission
• identify symptomatic contacts (such as, additional cases) as early as possible
• facilitate prompt clinical assessment by a HCP, laboratory diagnostic testing and treatment if signs or symptoms develop

In Canada, local PHAs are responsible for initiating contact tracing. Once a case is identified, they assess the need to begin contact tracing using the epidemiological and clinical information provided.

In determining the need to initiate contact tracing, the following factors should be considered:

• Evidence suggests that some cases may be infectious up to 4 days before the onset of symptoms
  • It is currently unknown what proportion of mpox cases transmit the virus pre-symptomatically and if the likelihood of pre-symptomatic transmission varies by route of transmission^{Footnote 49Footnote 50}.
• Cases are considered contagious until after the scabs have fallen off and there is evidence of epithelialization
• Several factors may influence transmission, such as the timing, type (for example, direct skin contact, respiratory route) and duration of exposure to the case, as well as any mitigation measures used during exposure for example, if the case was wearing a well-fitting medical mask or gloves)
  • Priority for public health management should be given to contacts with a high-risk exposure.

Previously, it was recommended that PHAs identify contacts who were exposed to an mpox case between the date of symptom onset and when their scabs fell off (with evidence of epithelialization). Based on the current evidence that pre-symptomatic transmission may occur, PHAs may consider extending contact tracing to certain contacts who were exposed to the case up to 4 days before their symptom onset^{Footnote 11Footnote 13Footnote 49Footnote 50Footnote 51Footnote 52Footnote 53Footnote 54Footnote 55Footnote 56Footnote 57}. This tracing may be done based on a risk assessment of the case's behaviour up to 4 days before their symptom onset. When assessing the risk, PHAs could consider whether the case had engaged in an activity with a greater risk of mpox transmission and/or visited a high-risk setting or event during this pre-symptomatic period. Refer to Table 1 on the classification of contacts by exposure risk level for a description and examples of high-risk exposure contacts.

The decision to trace contacts exposed to a case in the pre-symptomatic period will depend on whether PHAs are opting for a more rigorous contact management approach and if the necessary resources are available.

Risk assessment of contacts

It is recommended that all individuals who are contacts of a confirmed, probable or suspected case be rapidly identified and assessed by PHAs. Such assessment will determine their exposure risk level and the appropriate public health recommendations to follow.

To facilitate determining the public health recommendations, contacts are classified as either high, intermediate, or low risk according to their exposure in Table 1. This information is not intended to replace more personalized public health advice provided to contacts, which is based on clinical judgment and comprehensive risk assessments conducted by PHAs.

Depending on the PHA's approach to contact tracing (refer to the section on contact tracing), PHAs may classify a contact's risk of exposure to a symptomatic or a pre-symptomatic case.

Public health activities for contact management

For both high- and intermediate-risk mpox contacts, during the 21-day period since the contact's last exposure to the case, PHAs may:

• conduct active (or passive, where appropriate) public health monitoring for signs/symptoms and counselling
  • This may include informing the contact that signs/symptoms can occur even if vaccinated and can be mild or go unnoticed.
• provide instructions on what to do if signs/symptoms develop
• advise contacts that taking certain medications (such as acetaminophen, ibuprofen, acetylsalicylic acid) could mask early symptoms of mpox
  • Contacts who need to take these medications should advise the PHA.
• provide appropriate information on which PHMs to follow to reduce potential spread to others (refer to the following section on Public health measures recommendations for contacts)
• provide information on when and where to access diagnostic testing (as appropriate)
• explore means of reaching out to high-risk exposure contacts related to events in situations where contacts are unknown (for example, outreach to communities, stakeholder engagement, awareness campaign)
• provide advice to contacts on prophylaxis, especially in situations of high-risk exposure, and administer prophylaxis or facilitate connection with HCP for administration and follow-up, as appropriate

Public health measures recommendations for contacts

Recommendations in Table 2 apply for the 21-day period following the contact's last exposure to a known suspected (unless mpox is ruled out), probable or confirmed case.

Note: Along with determining exposure risk level, PHAs may further adjust PHM recommendations based on a thorough individual assessment of a contact's specific risk factors. For example, PHAs may consider if the contact:

• has previously received vaccination against smallpox or mpox, and if so, consider the vaccine product, number of vaccines received, and the time since the last vaccine dose
  • For more information on immunization recommendations based on the individual situation, refer to the Canadian Immunization Guide.
• has recovered from a previous mpox infection
• is at higher risk of severe disease, including individuals who are immunocompromised (for example, HIV with low CD4 levels), pregnant or young children including infants

Additional resources

• Federal, Provincial and Territorial Public Health Response Plan for the Management of the Mpox (monkeypox) Outbreak
• Public Health Ontario – Evidence Brief: Monkeypox Transmission Through Genital Excretions
• U.S. Department of Homeland Security Science and Technology – Evidence Brief: Master Question List for Monkeypox Virus
• World Health Organization: Mpox (monkeypox) Outbreak 2022
• Strategic framework for enhancing prevention and control of mpox 2024-2027.

Footnotes

References