The case in Broward County, Florida, is "related to international travel," the U.S. Centers for Disease Control and the Florida Department of Health said in a statement on Sunday, "and the person remains isolated."
The results of tests conducted by the CDC are expected soon. No other cases have been identified in the state, the release said.
The first monkeypox case in the United States was reported in Massachusetts on Wednesday. The disease, which is similar to human smallpox but milder, was found in a man who had recently traveled to Canada. Health officials said the case posed no risk to the public.
The second U.S. case was a New York City resident who tested positive for the virus on Friday, health officials said.
In Europe, more than 100 cases of the viral infection, which spreads through close person-to-person contact, have been reported recently.
Monkeypox, which mostly occurs in west and central Africa, is a viral infection that was first recorded in the Democratic Republic of Congo in the 1970s. Symptoms include fever, headaches and skin rashes starting on the face and spreading to the rest of the body.
(Reporting by Rich McKay in Atlanta; Editing by Muralikumar Anantharaman)
By Rich McKay