A second American has come down with monkeypox, a rare virus that causes pus-filled boils

• A US resident got monkeypox after returning from Nigeria to Maryland.
• A similar but separate case was reported in Dallas in July.

There is a second case of monkeypox in the US after a traveler returned from visiting Nigeria, the Centers for Disease Control and Prevention has confirmed.

The patient is currently in isolation in Maryland, the CDC wrote in a statement Wednesday.

The agency is working to contact any passengers who may have been exposed to the patient on the plane, although mandated mask-wearing likely protected them from significant risk.

This is the second case of monkeypox identified in the US this year. A man was hospitalized with the illness in June after returning to Dallas from Nigeria.

Monkeypox is a rare virus similar to smallpox, but milder. It's typically spotted in Central and West Africa, but infections have been identified on other continents six times before.

Most recently, three cases of monkeypox were reported in the UK during summer 2021. Like the cases in the US, the first infection originated in Nigeria, but other Brits were infected via close contact.

The virus can spread via respiratory droplets, similar to the coronavirus. But it's also contagious to anyone who touches the "pox" (lesions) or the fluids within them. The CDC has instructed healthcare providers in the US to be vigilant if they see any patients with poxvirus-like lesions.

Early symptoms of the monkeypox include fever, headache, muscle aches, exhaustion, and swollen lymph nodes. While the initial illness could be confused with the flu or COVID-19, the telltale, pimply rash typically appears within three days.

The illness can last two to four weeks, according to the CDC. Monkeypox is fatal for as many as 1 in 10 people who get sick in Africa. There's no proven treatment for it, but the smallpox vaccine and some antivirals can help control outbreaks.