Monkeypox virus (MPXV)

Updated June 27, 2022

NCCID Disease Debriefs provide Canadian public health practitioners and clinicians with up-to-date reviews of essential information on prominent infectious diseases for Canadian public health practice. While not a formal literature review, information is gathered from key sources including the Public Health Agency of Canada (PHAC), the USA Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO) and peer-reviewed literature.

This disease debrief was prepared by Heather Long and Wendy Xie. Questions, comments, and suggestions regarding this disease brief are most welcome and can be sent to

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Questions Addressed in this debrief:

  1. What are important characteristics of the Monkeypox virus?
  2. What is happening with current outbreaks of Monkeypox?
  3. What is the current risk for Canadians from Monkeypox?
  4. What measures should be taken for a suspected Monkeypox case or contact?

What are important characteristics of the Monkeypox virus?


Monkeypox virus is a double-stranded DNA virus belonging to the Orthopoxvirus genus in the family Poxviridae, which includes human variola (VAR), cowpox (CPV), and vaccinia (VAC) viruses. Monkeypox virus is a zoonotic disease, meaning it can be transmitted from animals to humans. Squirrels, Gambian poached rats, dormice, and non-human primates have been found to be susceptible to monkeypox virus, but further research is required to identify the true natural reservoir(s). There are two genetic clades of the monkeypox virus – the Central African (Congo Basin) and West African clades. The Congo Basin clade has caused more severe disease and is thought to be more transmissible.

Monkeypox virus transmission occurs when a person comes into direct or indirect contact with the body fluids or lesion materials of infected animals and humans, including contaminated materials.  Animal-to-human transmission may occur by bite or scratch, or through the preparation of bush meat. Human-to-human transmission of monkeypox virus is thought to occur primarily through respiratory droplets during sustained face-to-face contact, but may also be sexually transmitted through contact with the body fluids of an infected person. The virus may enter the body through broken skin (even if not visible), the respiratory tract, or mucous membranes of the eyes, nose, or mouth.

WHO: Health Topics – Monkeypox

CDC: About Monkeypox

Signs and Symptoms, and Severity

The symptoms of monkeypox virus are milder than, but similar to those of smallpox. One key difference is that monkeypox causes swollen lymph nodes (lymphadenopathy) while smallpox does not. The swelling can occur in many different locations on the body, or be localized, including lymph nodes of the neck and armpit. The incubation period (time from infection to onset of symptoms) for monkeypox is usually 7−14 days but can range from 5−21 days. In addition to swollen lymph nodes, early signs and symptoms may include fever, headache, muscle aches, exhaustion, backache, and chills. A rash develops on the body within 1 to 3 days (sometimes longer) after the appearance of fever, usually first on the face, then spreading to other parts of the body. The lesions progresses through the stages of macules, papules, vesicles, pustules, and finally scabs before falling off.

At the Meeting of the International Health Regulations Emergency Committee held on June 23, 2022, it was noted that the clinical presentation in the current monkeypox outbreak is often atypical. There are fewer lesions observed, and the lesions are often localized to the genital, perineal/perianal or peri-oral area. Some cases involve an asynchronous rash appearing prior to the prodromal phase (lymphadenopathy, fever, malaise).

Rash on human hand depicting a Monkeypox infection

Illness can last for 2-4 weeks depending on the health of the infected individual, the clade of the infecting virus, and the route of exposure. In Africa, the disease has been shown to cause death in as many as 1 in 10 people. Pregnant or breastfeeding women, children, persons with underlying medical conditions or immunocompromised individuals may be at higher risk for severe illness due to monkeypox infection.

PHAC: Public Health News – Monkeypox  

WHO: Monkeypox

WHO: Multi-country monkeypox outbreak in non-endemic countries

WHO: Meeting of International Health Regulations Emergency Committee (June 25, 2022)

CDC: About Monkeypox

CDC: Symptoms

CDC: Monkeypox – Clinical Recognition


Since the discovery of monkeypox virus in 1958, infections have been reported in people in central and western African countries: Cameroon, Central African Republic, Côte d’Ivoire, Democratic Republic of the Congo, Gabon, Liberia, Nigeria, Republic of the Congo, and Sierra Leone, with most infections occurring in the Democratic Republic of the Congo. Outside of Africa, most monkeypox cases in humans have been linked to international travel or exposure to imported animals, including cases in the United States, Israel, Singapore, and the United Kingdom. Many recently reported cases of monkeypox from Sweden, Italy, Belgium, USA and Canada are not linked to travel to the endemic areas of West/Central Africa, suggesting that there is local transmission within communities. In the UK, Spain and Portugal, cases of monkeypox have been reported amongst, but not exclusively in, men who have sex with men.

CDC: Monkeypox in the United States

EACS: Monkeypox in Europe

Laboratory Diagnosis :

Laboratory confirmation using specimens directly from the rash or biopsy (where feasible), using polymerase chain reaction (PCR) detection of viral DNA is preferred. Antigen and antibody detection methods may be less useful as these cannot distinguish between orthopoxviruses.

WHO: Health Topics – Monkeypox

Prevention and Control

The Centers for Disease Control and Prevention recommends a number of preventative measures that should be taken to reduce the risk of infection:

  • Avoid close contact with infected people, animals or contaminated materials whenever possible, including bedding that has been in contact with a sick patient.
  • Wear gloves and other personal protective clothing and equipment while taking care of the sick, whether in a healthcare facility or in the home.
  • Wash hands with soap and water or use an alcohol-based hand sanitizer after contact with an infected animal or human.
  • Isolate infected patients.

WHO: Health Topics – Monkeypox

CDC: About Monkeypox


On June 14, 2022, the World Health Organization released some interim guidance regarding vaccinations against monkeypox. Smallpox vaccines may provide some protection against monkeypox, but data are limited. First generation smallpox vaccines held in national reserves are not recommended as they do not meet current safety standards. Second and third generation smallpox vaccines, including Imvamune (or MVA-BN), may be useful for the prevention of monkeypox however mass vaccination is not required nor recommended at this time. Imvamune was approved for use in Canada in 2013, and the National Advisory Committee on Immunization (NACI) has recommended that the Imvamune vaccine may be offered to individuals with probable or confirmed cases of monkeypox. To date, human-to-human spread of monkeypox can be controlled via early diagnosis and treatment of symptoms, isolation of patient and contact tracing.

For individuals who are contacts of cases, post-exposure prophylaxis (PEP) with a second- or third-generation vaccine is recommended. To prevent the onset of disease, this vaccine should be provided within four days of first exposure and up to 14 days in the absence of symptoms.

For health care workers and laboratory staff at high risk of exposure to monkeypox cases, pre-exposure prophylaxis (PrEP) is recommended.

PHAC: Summary of NACI Interim Guidance (June 10, 2022)

NACI: Interim Guidance on the use of Imvamune in the context of monkeypox in Canada (June 2022)

WHO: Interim Vaccination Recommendations (June 14, 2022)


Most cases of monkeypox infection are self-limiting and symptoms will resolve on their own if rashes are left to dry or covered with a moist dressing to protect the area. There is currently no proven and safe treatment for monkeypox virus infection, however, vaccinia immune globulin (VIG) and antivirals may be recommended for severe cases. Tecovirimat (or TPOXX) is an antiviral that was developed to treat smallpox which was also approved for the treatment of monkeypox in January 2022. Antivirals Cidofovir, Brincidofovir and Tecovirimat are all currently being tested for activity against monkeypox virus.

WHO: Health Topics – Monkeypox

CDC: About Monkeypox

EACS: Monkeypox in Europe

What is happening with current outbreaks of Monkeypox?

As of June 24, 2022, The Public Health Agency of Canada (PHAC) reported 235 cases of monkeypox in Canada involving 184 cases in Quebec, 45 cases in Ontario, 4 cases in Alberta, and 2 cases in British Columbia.

As of June 24, 2022, the Centers for Disease Control and Prevention (CDC) in the United States reported 201 confirmed cases throughout the USA, and 4106 cases confirmed globally involving 47 countries, territories, and areas.

In a WHO news release dated June 25, 2022, a meeting of the International Health Regulations (2005) (IHR) Emergency Committee was held on June 23, 2022 whereby it was agreed that the current multi-country monkeypox outbreak does not constitute a Public Health Emergency of International Concern. This meeting does signal an escalation of the alert level of the international public health community.

PHAC: Monkeypox Outbreak Update

WHO: Meeting of International Health Regulations Emergency Committee (June 25, 2022)

CDC: US Monkeypox Outbreak Update

CDC: Global Monkeypox Outbreak Update

What is the current risk for Canadians?

On June 2, the WHO assessed the risk to the general public to be moderate as this is the first time monkeypox has been reported concurrently in both endemic and non-endemic countries. This risk would increase if the virus continued to establish itself within the human population in non-endemic countries, but so far, this has not been the case.

There is added risk to health workers if they are not using adequate infection prevention and control (IPC) measures or wearing appropriate personal protective equipment (PPE) to reduce the risk of transmission. In Canada, cases of human transmission have involved close contact with an infected individual, but the risk to the general public remains low. However, this is an ongoing investigation in Canada and around the world, and more information is needed to determine the risk to Canadians. The Public Health Agency of Canada (PHAC) will continue to release recommendations to minimize the risk of infection and provide updates related to confirmed cases. Given that the monkeypox virus is spread through close contacts, PHAC advises physical distancing, handwashing, and wearing masks to reduce the risk of infection. While the risk of infection for the general population is low, PHAC recommends that Canadians and health care providers should be aware of the symptoms of monkeypox regardless of travel history.

The Centers for Disease Control and Prevention (CDC) does not see any evidence to date that monkeypox poses a high risk to domestic pets. In a past outbreak in the United States in 2003, there was no evidence to suggest the disease was spread from humans to their domestic pets. Regardless, the CDC recommends anyone with monkeypox to avoid contact with their pets and make arrangements for someone to care for their pets until they recover.

PHAC: Monkeypox – Risks

WHO: Multi-country monkeypox outbreak update (June 4, 2022)

CDC Statement on Human to Domestic Pet Transmission (June 2022)

What measures should be taken for a suspected Monkeypox case or contact?

Canadians should be made aware of the symptoms of monkeypox and are advised to report any concerns to their health care provider without delay. The Public Health Agency of Canada has sent alerts to public health authorities to assist health care providers to identify patients showing signs or symptoms consistent with monkeypox, regardless of any reported travel or any specific risk factors.

Health care providers should ensure patients with suspected cases of monkeypox isolate from other family members and pets and should only leave home to seek medical care. The receiving healthcare setting should be notified prior to the patient’s arrival, and patients with suspected, probable, or confirmed monkeypox infection should not use public transportation. Lesions should be covered with long sleeves and pants, and surgical masks should be worn by the patient and all family members in the household. Surgical gloves should be worn when in direct contact with lesions and disposed of immediately in accordance with the local health regulations.

Government of Canada: Monkeypox – For health professionals – Infection prevention and control guidelines

CDC: Monkeypox – For Clinicians