What is the history of monkeypox?

Monkeypox has a relatively recent history. People first discovered it in monkeys in 1958, although a “vesicular disease in monkeys” was described in the 1860s. The disease, and eventually the causative virus, was named monkeypox because the lesions (pox) seen in monkeys developed like other known pox-forming diseases (pustules that eventually break open, ulcerate, crust over, and some pox form scars in the skin). Later studies showed the “monkeypox” virus was actually sustained endemically in African rodents. It was not until 1970 in Africa (Zaire, now the Democratic Republic of Congo also termed Republic of the Congo, DRC, and Congo), when a 9-year-old boy (who developed smallpox-like lesions) was the first person to eventually be diagnosed with monkeypox. This situation initially caused concern that smallpox may also have an animal reservoir or endemic population that would make eradication of smallpox impossible. Fortunately, this was not the case because monkeypox was found to be a different species of poxvirus, and smallpox was eradicated from the human population by vaccinations in 1979 (currently, only a few research labs have access to smallpox viruses). Monkeypox is now the major Orthopoxvirus (also termed orthopox) that infects humans and fortunately, not frequently. However, vigilance is warranted, as there have been several outbreaks of monkeypox since the 1970s. Although most have occurred in Africa (mainly western and central Africa), there was an outbreak in the U.S. in 2003. This apparently happened when an animal distributor either housed or transported monkeypox-infected African rodents (Gambian rats) with prairie dogs that people later purchased as pets, became “sick,” and transmitted the disease to their owners. Other animals like the rope squirrel (Funisciurus anerythrus) and the sun squirrel (Heliosciurus rufobrachium) may transmit the virus to humans in Africa.

In 2017, an outbreak of monkeypox began in Nigeria. This large outbreak is thought to be triggered by river flooding that has caused infected wild animals (especially rodents and monkeys) to more closely associate with humans, thus spreading this zoonotic (transmitted to humans from animals) disease. From 2017 to the present, Nigeria has recorded 446 cases. In September 2018, Dr. Beadsworth in England reported treating three people with monkeypox who had visited Nigeria. The three patients likely were exposed to the virus while visiting Nigeria. On July 15, 2021, a person was diagnosed with monkeypox in Dallas, Texas, and the CDC confirmed this. He traveled by air from Nigeria to Atlanta, Georgia, and then flew on to Dallas, Texas. Both airlines he used had required masks, so the CDC thinks the risk is low for transmission of the disease. However, the CDC is currently assessing the risk of transmission to people who had close contact with the infected traveler.