A Maryland resident who recently returned to the country on a flight from Nigeria has tested positive for monkeypox, the Centers for Disease Control and Prevention announced Wednesday. It is the second confirmed case of the rare disease in the U.S. since an outbreak infected 43 people in 2003. 

The infected person is experiencing mild symptoms. They are not hospitalized but remain in isolation in Maryland, the Maryland Department of Health said in a press release. The CDC said lab tests confirmed the case is the same strain of the virus that has been re-emerging in Nigeria since 2017. The Nigerian strain is generally less severe, the state’s health department said.

“Public health authorities have identified and continue to follow up with those who may have been in contact with the diagnosed individual,” deputy secretary for public health at Maryland’s Department of Health Dr. Jinlene Chan said in a statement. “Our response in close coordination with CDC officials demonstrates the importance of maintaining a strong public health infrastructure.”

While the disease can spread through respiratory droplets, the CDC said the risk is low since passengers on the flight with the infected person were required to wear masks. The state health department said that no special precautions for the general public are recommended. 

Monkeypox, which is in the same family of viruses as smallpox, is a very rare but potentially deadly viral infection that begins with flu-like symptoms and progresses to a rash on the body, according to the CDC. The disease typically lasts two to four weeks. It is also spread through direct contact with bodily fluids or skin lesions, or by contaminated materials such as bed sheets. Those who do not present symptoms are not capable of transmitting the virus. 

U.S. healthcare providers are urged by the CDC to be on the lookout for poxvirus-like lesions on people, especially among travelers returning from central or western Africa. The CDC said clinicians should report suspected cases of monkeypox immediately to the appropriate health authorities.

Prior to this case, human monkeypox infections have only been documented on six different occasions outside of Africa, according to the CDC. 

In July, a Dallas, Texas, resident who had recently returned from Nigeria tested positive for monkeypox in the first confirmed case in the country since an outbreak almost 20 years ago. More than 200 people who were in possible contact with the infected person were asked to monitor their health for 21 days following the diagnosis. After the monitoring period ended, no additional cases were identified, the CDC said. 

In 2003, 47 people fell ill after imported African rodents infected prairie dogs with monkeypox, which subsequently infected humans, the CDC said. It was the first time humans had been infected outside of Africa. The outbreak led government officials to search across 15 states for infected prairie dogs. As a result, importing African rodents into the U.S. was banned.