The monkeypox virus causes infection, which results in the illness we know as monkeypox. This virus belongs to the same genus as the smallpox, camelpox, and other orthopoxviruses. It is a zoonotic illness, which means that animals may spread it to humans. Despite the name, the virus does not primarily reside in monkeys. Small rodents like squirrels, dormice, rats, and mice transmit it most often.

In the Democratic Republic of the Congo in 1970, monkeypox was discovered in people for the first time. Until now, it has been regarded as an endemic illness on the African continent's rainforest regions, where thousands of cases are reported annually. Only the US, UK, Singapore, and Israel have reported occurrences outside of Africa. The cause of every previous epidemic was either imported cases or interaction with animals from endemic regions.