The Ministry of Health and Long-Term Care is working with Health Canada on the investigation of the human monkeypox outbreak in the United States.

This is the first time that monkeypox has ever been reported in the western hemisphere. There are no cases in Canada.

All Medical Officers of Health and Associates have been advised by this ministry of infection control measures, preventive recommendations for pet owners with ill animals and how to submit specimens for analysis.

Monkeypox is a rare viral disease that is found mostly in the rainforest countries of central and west Africa. The disease is called "monkeypox" because it was discovered in laboratory monkeys in 1958. Studies of animals in Africa later found serologic evidence of infection in ground squirrels, which are thought to have an important role as a natural host for the disease. Laboratory studies showed that monkeypox infection also can occur in rats, mice, and rabbits.

In 1970, monkeypox was identified as the cause of a smallpox-like illness in humans in remote African locations. In early June 2003, monkeypox was reported among several residents in the United States who became ill after having contact with sick prairie dogs. This is the first evidence of community-acquired monkeypox virus infection in the United States.

The disease is caused by Monkeypox virus, which belongs to the orthopoxvirus group of viruses. Other viruses in this group that can cause infection in humans include variola (smallpox), vaccinia (used in smallpox vaccine), and cowpox viruses.

In humans, the clinical features of monkeypox are similar to those of smallpox, except that swelling of lymph nodes is associated with monkeypox. About 12 days after exposure, the illness begins with fever, headache, muscle aches, backache, swollen lymph nodes, a general feeling of discomfort, and exhaustion. Within 1 to 3 days (sometimes longer) after onset of fever, the patient develops a papular rash (i.e., raised bumps), often first on the face but sometimes initially on other parts of the body. The lesions usually develop through several stages before crusting and falling off. The illness typically lasts for 2 to 4 weeks. In Africa, monkeypox is fatal in as many as 10% of people who get the disease; the case fatality ratio for smallpox was about 30% before the disease was eradicated.

People can get monkeypox from an infected animal through a bite or direct contact with the infected animal's blood, body fluids, or lesions. The disease also can be spread from person to person, but it is much less infectious than smallpox. The virus is thought to be transmitted by large respiratory droplets during direct and prolonged face-to-face contact. In addition, monkeypox can be spread by direct contact with body fluids of an infected person or with virus-contaminated objects, such as bedding or clothing.

There is no specific treatment for monkeypox. Smallpox vaccine has been reported to reduce the risk of monkeypox among previously vaccinated persons in Africa. The potential role of smallpox vaccine in persons who have been exposed to monkeypox is being assessed. Antiviral drugs, such as cidofovir, are being evaluated for the treatment of monkeypox.

Source: CDC, Atlanta, USA / June 2003

Centres for Disease Control and Prevention (USA)

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