Mpox (formerly called monkeypox) was first identified in 1958 in a laboratory setting, not in the wild. Scientists in Copenhagen discovered the virus when a colony of research monkeys developed a smallpox-like illness during two separate outbreaks. Despite the name, monkeys aren’t the natural home of the virus. The real story of where it came from, how it jumped to humans, and how it eventually spread worldwide is more complicated than the name suggests.
The 1958 Discovery in Lab Monkeys
The virus was first isolated in late 1958 at a research facility in Copenhagen, Denmark. Cynomolgus monkeys, a species commonly used in laboratories, broke out in a disease that looked a lot like smallpox. Researchers identified the pathogen as a new virus and named it after the animals it was found in. But this was a case of misleading naming: the monkeys were incidental hosts, not the species that naturally carries the virus in the wild.
The First Human Case in 1970
It took another 12 years before mpox was confirmed in a person. In 1970, a nine-month-old boy in what was then Zaire (now the Democratic Republic of the Congo) became the first documented human case. He was the only member of his family who hadn’t received a smallpox vaccine, which likely left him vulnerable. The virus had probably been infecting people in Central and West Africa for much longer, but without laboratory testing, those cases would have been mistaken for smallpox or chickenpox.
Where the Virus Actually Lives in Nature
Despite the name, the virus’s true reservoir is almost certainly rodents, not primates. Researchers have detected the virus in a range of African mammals, including Gambian pouched rats, rope squirrels, dormice, and several species of tree squirrels. A 2023 ecological study comparing the geographic range of the virus with the habitats of potential hosts concluded that a small African tree squirrel called Funisciurus anerythrus is the most probable natural reservoir.
Humans typically catch the virus from animals through bites, scratches, or direct contact with an infected animal’s blood or body fluids. Hunting, skinning, trapping, and cooking wild animals are all documented routes of transmission. A 2003 outbreak in the United States, the first outside Africa, was traced directly to a shipment of wild rodents imported from Ghana, including pouched rats, rope squirrels, and dormice that then infected pet prairie dogs sold to the public.
Two Distinct Viral Clades
Not all mpox is the same. The virus comes in two major genetic lineages, or clades, that evolved separately in different parts of Africa and cause different levels of illness.
Clade I circulates in Central Africa, including the Democratic Republic of the Congo, the Republic of the Congo, Gabon, and the Central African Republic. Historically it was considered the more dangerous form, though recent data put the mortality rate for Clade Ia at around 2.5%, with most deaths occurring in people with weakened immune systems, malnourished children, or those without access to good medical care. A newer sublineage, Clade Ib, was first identified in the DRC and has since spread to neighboring countries. Its fatality rate appears lower, under 0.5%.
Clade II is found in West Africa, particularly Nigeria, Ghana, and surrounding countries. Clade IIa has a mortality rate around 1% based on limited data. Clade IIb, the strain responsible for the global outbreak that began in 2022, has a mortality rate below 0.1%, making it the least lethal form.
How the 2022 Global Outbreak Started
The event that brought mpox to worldwide attention began with a single traveler. On April 29, 2022, a British resident who had recently visited Nigeria developed symptoms consistent with mpox. He returned to the United Kingdom on May 4, and his case was confirmed on May 7. By mid-May, health officials were seeing community transmission in the London area, with no direct link to travel from Africa.
The virus spread fast. By June 13, 2022, more than 780 cases had been reported across 27 countries, with over 50 people hospitalized. The United Kingdom led the count with 207 confirmed cases, followed by Spain (156), Portugal (138), Canada (58), and Germany (57). Within months, Clade IIb mpox had reached more than 100 countries that had never seen the virus before. The World Health Organization declared it a public health emergency of international concern.
Why the Name Changed to Mpox
On November 28, 2022, the WHO announced it would begin using “mpox” as the preferred name for the disease. The decision came after reports of racist and stigmatizing language directed at people and communities during the 2022 outbreak. The organization set a one-year transition period during which both names would be used before “monkeypox” was fully phased out. The name monkeypox had always been scientifically misleading anyway, since monkeys are not the virus’s natural host.
The Situation in Africa Today
While the global emergency declaration was lifted in September 2025, mpox continues to spread in parts of Africa. Community transmission of Clade Ib persists in at least 12 African countries, including the DRC, Burundi, Kenya, Uganda, South Africa, and Mozambique. Namibia reported its first cases in late 2025, linked to travel within the continent. The WHO still classifies the risk from Clade Ib as moderate for certain populations and has extended its standing recommendations through August 2026, urging countries to maintain surveillance, strengthen laboratory testing, and ensure vaccine access for people at highest risk.