The first case of monkeypox in the U.S. was reported in Massachusetts Wednesday afternoon, following a small outbreak of cases in the United Kingdom. 

The Massachusetts Department of Public Health said an adult male who had recently traveled to Canada contracted monkeypox, though they said the confirmed case poses no risk to the general public. Massachusetts health officials are working alongside the Centers for Disease Control and Prevention to identify close contacts. 

This is not the first documented case of monkeypox in the U.S. There were two cases reported in 2021, both from Americans who had returned from travel to Nigeria.

In 2003, there was a monkeypox outbreak of 47 cases across six states after all people infected had contact with pet prairie dogs. According to the CDC, this was the first time that monkeypox was reported outside of Africa.

Given the recent outbreak of cases of the rare disease, it’s worth exploring what monkeypox is — and what it isn’t. 

According to the World Health Organization, monkeypox is a virus that typically presents with a fever, rash and swollen lymph nodes. It is spread through direct contact with “the blood, bodily fluids or cutaneous or mucosal lesions of infected animals,” though WHO says human-to-human transmission is “relatively limited.” The incubation period of monkeypox is usually from six to 13 days, but can also range from five to 21 days. 

There is no proven treatment for monkeypox, according to the Cleveland Clinic, and symptoms last from two to four weeks before going away on their own. There is a vaccine: Jynneos, an attenuated live virus vaccine approved by the Food and Drug Administration for the prevention of monkeypox. 

There are two strains of monkeypox, Central African and West African. The former causes more severe infections and is more likely to cause death. WHO estimates that up to 10% of people infected with monkeypox may die, with most deaths affecting younger patients.

Monkeypox was discovered in 1958 and first identified in humans in 1970. The first reported case of the disease in the U.S. came during the same week that the nation’s death total from COVID-19 surpassed 1 million.