A case of monkeypox has been confirmed in a person in Maryland, the Centers for Disease Control and Prevention reported Wednesday.
It is the second case this year involving a person who had traveled to the United States from Nigeria. The first case was in a Texas resident in July and is not related to the Maryland case.
Before this year, the illness had not been seen in the U.S. since a 2003 outbreak, which sickened 47 people.
Symptoms of the virus include fatigue, fever, headache and muscle aches. Within a week to 14 days after exposure, patients develop a bumpy rash that spreads to the entire body.
Most patients recover within a month, though they are considered contagious until the raised bumps have scabbed over and fallen off. The illness is rarely fatal.
The CDC said this latest case matches a strain of the virus that has been circulating in Nigeria for several years. The patient is in isolation, the agency said.
The CDC and other health officials are now working with the airline on which the patient traveled from Nigeria to contact fellow passengers.
The monkeypox virus spreads via respiratory droplets when an infected person sneezes or coughs. Because masks were required on the flight, the CDC said the risk that anyone else on the plane was infected is low.
Still, the agency is asking that doctors be alert to any unusual rashes on patients, especially if they have traveled from Nigeria.