Monkeypox got its name because the virus was first discovered in monkeys. In 1958, researchers at an animal facility in Copenhagen, Denmark, identified the virus during a nonfatal outbreak among captive cynomolgus monkeys. They isolated the virus from pustules on the sick animals, and since monkeys were the first known hosts, the name “monkeypox” stuck. It’s a straightforward origin story, but the name turned out to be misleading in almost every way.
What Happened in 1958
The Copenhagen facility housed monkeys used for research. When some of the animals developed pox-like skin lesions, scientists isolated the virus from their pustules by incubating samples in eggs, a standard lab technique at the time. Because the virus came from monkeys and caused pox-like symptoms, naming it “monkeypox” followed the conventions of the era. Viruses were routinely named after the animal or location where they were first found.
No one knew at the time that monkeys were essentially bystanders. The virus had infected them, but monkeys weren’t the species carrying and spreading it in the wild.
Monkeys Aren’t the Real Source
Despite the name, the actual reservoir of the virus is almost certainly rodents, not primates. The definitive host hasn’t been confirmed, but ecological research points strongly to African tree-dwelling squirrels, particularly a species called Thomas’s rope squirrel. This small rodent, found across Central and West African forests, shows the best ecological overlap with areas where the virus circulates. The virus has been isolated from rope squirrels in the Democratic Republic of the Congo and its full genome sequenced from those samples.
Other rodents have also tested positive, including giant pouched rats, dormice, and several additional squirrel species. Monkeys can catch the virus, but they appear to be secondary hosts, likely picking it up through contact with infected rodents while sharing forest trees. In other words, the name “monkeypox” points to the wrong animal entirely.
The First Human Case
The virus jumped to humans 12 years after it was identified in the lab. In 1970, the first human case was recorded in the Democratic Republic of the Congo. From there, sporadic outbreaks continued for decades, mostly in Central and West Africa, before the virus gained worldwide attention during a large outbreak in 2022.
The virus belongs to the same family as smallpox. Both are classified in the Orthopoxvirus genus, a group of 13 related species that also includes the virus used in the original smallpox vaccine. That family connection is why monkeypox symptoms, including fever, swollen lymph nodes, and fluid-filled skin lesions, resemble a milder version of smallpox.
Why the Name Changed to Mpox
In November 2022, the World Health Organization officially recommended replacing “monkeypox” with “mpox.” The change came after the global outbreak earlier that year triggered a wave of racist and stigmatizing language online and in public settings. Multiple countries and public health figures asked the WHO to intervene.
The reasoning went beyond stigma. The WHO laid out several criteria for the new name: it needed to be scientifically appropriate, easy to pronounce across languages, free of geographic or animal references, and unlikely to harm trade, travel, or animal welfare. “Mpox” checked those boxes. It also avoided reinforcing the inaccurate association with monkeys, which had real consequences. During the 2022 outbreak, there were reports of hostility directed at monkeys and calls to cull primate populations, despite monkeys playing no meaningful role in spreading the virus to humans.
Both names are currently in use. The WHO designated a one-year transition period, and “mpox” has since become the standard in scientific literature and public health communications. “Monkeypox” still appears widely in casual use and older research.
Why Virus Names Get It Wrong
Monkeypox is far from the only virus with a misleading name. The tradition of naming diseases after the place or animal where they were first detected often produces labels that age poorly as scientists learn more. Spanish flu almost certainly didn’t originate in Spain. Guinea worm isn’t unique to Guinea. These names linger because they enter common use before the science catches up.
The WHO updated its naming guidelines in 2015 specifically to prevent this problem, recommending that new diseases avoid geographic, animal, and cultural references. Mpox was one of the first high-profile retroactive applications of those guidelines. The virus itself hasn’t changed. It’s the same pathogen first pulled from a sick monkey in a Danish lab in 1958. The name just finally caught up with what scientists have known for decades: monkeys were never the main character in this story.