Monkeypox has caught the attention of US President Joe Biden, who said Sunday that people should be on guard against the disease which has the potential for "consequential" impact, if it were to spread further.
Several cases of monkeypox have been detected in North America and Europe since early May, sparking concern the disease, endemic in parts of Africa, is spreading.
The US leader, on his maiden trip to Asia as president, said in Seoul that health officials have not fully briefed him about "the level of exposure" in the United States.
"But it is something that everybody should be concerned about," Biden told reporters before boarding Air Force One to fly to Tokyo.
"It is a concern, in that, if it were to spread, it would be consequential," he added.
"We're working on it hard to figure out what we do, and what vaccine if any might be available for it."
The first US case in the recent global spate was reported on May 18 in Massachusetts, which was joined on Sunday by Florida.
Health authorities said they were investigating the southern state's first presumptive case of monkeypox in someone who had recently traveled abroad.
There have been thousands of human infections in parts of Central and Western Africa in recent years but it is rare in Europe and North America.
Most people recover within several weeks and monkeypox has only been fatal in rare cases.
The World Health Organization said that as of Saturday there were 92 confirmed cases of the disease in countries where monkeypox is not endemic.
The virus is transmitted to humans from animals, with symptoms very similar to smallpox but less severe clinically.
© Agence France-Presse