The monkeypox virus is an orthopoxvirus that causes mpox (monkeypox), a
disease with symptoms similar to smallpox, although less severe. While smallpox
was eradicated in 1980, mpox continues to occur in countries of central and
west Africa. Since May 2022, cases have also been reported from countries
without previously documented mpox transmission outside the African region. Two
distinct clades of the monkeypox virus have been identified: Clade I
(previously known as the Congo Basin (central African) clade and Clade II (the
former west African clade).
Mpox is a zoonosis, a disease that is transmitted from animals to humans,
with cases often found close to tropical rainforests where there are animals
that carry the virus. Evidence of monkeypox virus infection has been found in
animals including squirrels, Gambian pouched rats, dormice, different species
of monkeys and others.
The disease can also spread from humans to humans. It can be transmitted
through contact with bodily fluids, lesions on the skin or on internal mucosal
surfaces, such as in the mouth or throat, respiratory droplets and contaminated
objects.
Detection of viral DNA by polymerase chain reaction (PCR) is the preferred
laboratory test for mpox. The best diagnostic specimens are taken directly from
the rash – skin, fluid or crusts, or biopsy where feasible. Antigen and
antibody detection methods may not be useful as they do not distinguish between
orthopoxviruses.