Monkeypox virus (MPV, MPXV, or hMPXV) is a species of double-stranded DNA virus that causes monkeypox in humans and other mammals. Monkeypox virus is a zoonotic virus belonging to the orthopoxvirus genus, making it closely related to the variola (VARV), cowpox (CPX), and vaccinia (VACV) viruses. MPV is oval-shaped with a lipoprotein outer membrane. The genome is approximately 190 kb.
The variola and monkeypox virus are both orthopoxviruses, and so the smallpox vaccine is effective against monkeypox if given within 3–5 years before contracting the disease. The clinical presentation of Monkeypox is similar to smallpox, but with a milder rash and lower mortality rate. The virus is transmissible between animals and humans, by direct contact to the lesions or bodily fluids. Monkeypox was given its name after being isolated from monkeys, but the majority of the carriers of this virus are rodents.
Variation in virulence of the virus has been observed in isolates from Central Africa, where strains are more virulent than those from Western Africa. The two areas have distinct clades of the virus, termed clade I, formerly the Congo Basin (Central African) clade, and clade II, formerly the West African clade. Though there are many natural hosts for the monkeypox virus, the exact reservoirs and how the virus is circulated in nature needs to be studied further.
Though the monkeypox virus has been circulating around the globe for the past several decades, first discovered in 1970, research on this virus is minimal compared to other orthodox viruses. Most of the what is known about the monkeypox virus is information pieced together from studies on different but related viruses, notably other orthopox viruses.