Overview

Mpox (formerly known as monkeypox) is an infectious disease caused by the monkeypox virus, typically transmitted from animals to humans, that causes a disease with symptoms similar to, but less severe, than smallpox.

Since May 2022, numerous cases and outbreaks of mpox have been reported across several European, American, African, Western Pacific, Eastern Mediterranean, and South-East Asian countries, where mpox has not been typically found and where there are no identified associations with travel to mpox endemic countries.

Mpox has a broad range of clinical presentations with common symptoms that include:

  • fever
  • new rash/lesions in the mouth, genital or peri-anal region
  • rectal pain
  • lymphadenopathy

Mild and subclinical infections are suspected to be the cause of ongoing transmission. Clinicians should keep mpox on their differential diagnosis and have a low threshold to test in risk groups with compatible signs and symptoms. Mpox is typically mild and self-limiting, with most people recovering within 2 to 4 weeks. However, severe illness can occur in some individuals.

The main route of mpox virus transmission is:

  • direct close contact (skin-to-skin)
  • direct contact with skin lesions/scabs, bodily fluids, and mucus membranes in the mouth, tongue, and genitalia

Other less common routes of transmission include:

  • respiratory transmission
  • contact with materials contaminated with monkeypox virus (such as contaminated bedding, linens, towels, lesion dressings or needles)
  • close but non-direct contact (non-sexual household contacts, for example) can occur

These less common routes of transmission have not been observed in Ontario data and investigations to date.

On June 16, 2022, mpox was designated as a Disease of Public Health Significance (DOPHS) requiring the reporting of mpox cases (see Appendix 1: Case Definitions and Disease Specific Information, Disease: Smallpox and other Orthopoxviruses including Monkeypox) directly to the local medical officer of health in accordance with the reporting requirements in the Health Protection and Promotion Act, as per routine disease processes.

Vaccination

Imvamune® is authorized in Canada for protection against mpox. Imvamune® is a two-dose series, given 28 days apart. People with a history of smallpox vaccine should receive one dose of Imvamune® as prior vaccination against smallpox provides some cross-protection against mpox.

Imvamune® should be considered for the following:

  • Pre-exposure vaccination - when Imvamune® is administered before known exposure to the virus.
  • Post-exposure vaccination - when Imvamune® is administered for individuals who have had a high-risk exposure to a probable or confirmed case of mpox, or within a setting where transmission is happening.

Eligibility for Imvamune® for pre-exposure vaccination in Ontario is as follows:

  • Two-Spirit, non-binary, transgender, cisgender, intersex, or gender-queer individuals who self-identify or have sexual partners who self-identify as belonging to the gay, bisexual, pansexual and other men who have sex with men (gbMSM) community and at least one of the following:
    • had a confirmed sexually transmitted infection (STI) within the last year
    • have or are planning to have 2 or more sexual partners or are in a relationship where at least one of the partners may have other sexual partners
    • have attended venues for sexual contact (such as bathhouses, sex clubs) recently or may be planning to, or who work or volunteer in these settings
    • have had anonymous sex (such as using hookup apps) or may be planning to or are a sexual contact of an individual who engages in sex work
  • Individuals who self-identify as engaging in sex work or are planning to, regardless of self-identified sex or gender

Household and/or sexual contacts of those identified for pre-exposure vaccination eligibility in parts A and B above and who are moderately to severely immunocompromised or pregnant .

Imvamune® given for post-exposure vaccination requires an assessment of the risk of exposure by the public health unit. The first dose should be offered ideally within 4 days (up to 14 days) from the date of the last exposure to individuals who are a high-risk contact of a confirmed or probable case of mpox. The second dose should be offered at least 28 days after the first dose. Anyone who self-identifies as a high-risk contact of a confirmed or probable case of mpox should contact their local public health unit for further assessment to see if post-exposure vaccination would be recommended.

Research laboratory employees working directly with replicating orthopoxviruses are eligible to receive two doses of Imvamune®, 28 days apart as post-exposure vaccination or pre-exposure vaccination if there is an ongoing risk of exposure.

It is important to receive both doses for optimal protection. Recent studies have shown vaccine effectiveness to be between 66-83% for patients with a 2-dose vaccine series. As such, clinicians should continue to promote first and second dose vaccination. Booster doses are not recommended at this time.

Treatment

Tecovirmat (TPoxx®) is an antiviral medication that inhibits the production of an orthopoxviral envelope protein required for cell-to-cell viral dissemination .

TPoxx® is authorized for sale and use in Canada for the treatment of human smallpox disease in adults and pediatric patients weighing at least 13 kg based on limited clinical testing in humans. TPoxx® has been approved in other jurisdictions including the European Medicines Agency (EMA) which has authorized TPoxx® for the treatment of mpox, cowpox and smallpox.

It does not have an approved indication for the treatment of mpox in Canada. However, a licensed healthcare professional may request this drug for eligible patients based on their clinical judgement for treating severe mpox infections.

Mpox in animals

Some animals can become infected with mpox, including:

  • rodents (such as rats, mice, hamsters, gerbils, squirrels, chipmunks)
  • rabbits
  • hedgehogs
  • opossums
  • non-human primates (such as monkeys)

Mpox has been reported on a dog that had close contact with its infected owners. As such, precautions should be taken to prevent exposure of the virus to domestic and wild mammals.

Veterinarians that suspect an animal has been infected with mpox should call the Ontario Ministry of Agriculture Food and Rural Affairs at 1-877-424-1300 to discuss management plans.

Resources for health care providers

Document TitleDescription
Mpox Vaccine (Imvamune®) Guidance for Health Care ProvidersGuidance for health care providers administering the Imvamune® vaccine
Imvamune® Vaccine Storage and Handling GuidanceGuidance for vaccine handling, storage, and transport of the Imvamune® vaccine
Mpox Vaccine Information SheetInformation for patients and the public about the vaccine for mpox
Mpox Antiviral Guidance for Health Care ProvidersGuidance for health care providers on how to order and administer Tpoxx®
Mpox Antiviral Information SheetInformation for patients and the public about treatment for mpox
Reference guide comparing mpox, varicella, measles and hand-foot-and-mouth diseaseInformation for health care providers on comparing mpox, varicella, measles, and hand-foot-and-mouth disease

Additional resources