Monkeypox is something “everybody should be concerned about” and the US is looking into what kind of treatments and vaccines are available, President Joe Biden has said.
The World Health Organisation has identified about 80 monkeypox cases globally, and roughly 50 more suspected cases.
Cases of the smallpox-related disease have previously been seen only among people with links to central and West Africa.
A leading doctor told Sky News the UK is facing a “significant rise” in cases over the next week, with 20 infections confirmed so far.
Speaking in South Korea before boarding a flight to Japan, Mr Biden said US health officials were looking into possible treatments and vaccines.
“It is something that everybody should be concerned about,” the US president said.
“We’re working on it hard to figure out what we do and what vaccine, if any, may be available for it.
“It is a concern in a sense that if it were to spread, it’s consequential.”
Monkeypox, which originates in primates and other wild animals, causes fever, body aches, chills and fatigue in most patients.
People with severe cases can develop a rash and lesions on the face, hands and other parts of the body.
New infections have been reported across Europe and North America this weekend, while Israel recorded its first case on Sunday.
Professor David Heymann, an infectious disease specialist at the World Health Organisation, said he believed the virus had entered the population as a “sexual form”.
He said: “What seems to be happening now is that it has got into the population as a sexual form, as a genital form, and is being spread as are sexually transmitted infections, which has amplified its transmission around the world.”
The president of the British Association for Sexual Health and HIV told Sky News she expected more monkeypox cases to be identified around the UK in the coming week.
Dr Claire Dewsnap said: “What worries me the most is there are infections across Europe, so this has already spread.
“It’s already circulating in the general population.
“It could be really significant numbers over the next two or three weeks.
“I’m definitely expecting a significant rise over this next week.”
The UK Health Security Agency has said a notable proportion of recent cases in Britain and Europe have been found in gay and bisexual men.
In Spain, most of its 30 confirmed cases have been linked to a sauna in Madrid.
To date, no one has died in the outbreak.
Dr Dewsnap said some health workers have received the smallpox vaccine, which can be effective against monkeypox, and talks are taking place about giving doses to “potential risk groups”.