More than 30 cases of monkeypox have now been reported around the U.S.
According to the Centers for Disease Control and Prevention (CDC), there are now 31 confirmed monkeypox and orthopoxvirus cases nationwide.
New York leads the 13 states with reported infections, confirming seven. California has six, Florida has four and Colorado has three.
Illinois and Utah have two cases each.
There is one case reported in Washington state, Virginia, Pennsylvania, Massachusetts, Hawaii, Georgia and the District of Columbia.
The World Health Organization (WHO) said Sunday that more than two dozen countries where monkeypox virus is not endemic have reported 780 cases.
However, no monkeypox deaths outside of Africa have been identified.
The agency said the sudden and unexpected detection "suggests that there might have been undetected transmission for some unknown duration of time followed by recent amplifier events."
Previously, a leading adviser to the WHO said the outbreak in Europe and beyond was likely spread by sex at two recent raves in Spain and Belgium.
Monkeypox spreads when there is close contact with an infected individual, but it is not yet known whether it is being transmitted now exclusively by sex.
Although the majority of new monkeypox cases have been seen in gay or bisexual men, experts caution that anyone is at potential risk.
It also remains unclear if people could spread monkeypox without symptoms or if the disease might be airborne.
Traditionally, monkeypox virus is spread by touching or getting bitten by infected wild animals in western and central Africa.
Notably, U.S. health officials said last week that genetic analysis of recent cases suggests there are two strains in the country.
Monkeypox, which is related to smallpox, has milder symptoms.
Some of those symptoms include fever, chills, rash and aches, before lesions develop.
The Associated Press contributed to this report.