The World Health Organization says more than 1,000 people have been infected with monkeypox in the current outbreak mainly in Western nations.
WHO Director-General Tedros Adhanom Ghebreyesus spoke at a news conference on Wednesday.
He said, "More than 1,000 confirmed cases of monkeypox have now been reported to the WHO from 29 countries that are not endemic for the disease." He added that no deaths have been reported in those countries.
Tedros said, "The risk of monkeypox becoming established in non-endemic countries is real."
He called on affected countries to make efforts to curb further infections, such as tracking moves of infected people.
Rosamund Lewis, WHO technical lead for monkeypox, said human-to-human transmission is mainly caused by contact at close distances, including physical contact.
But Lewis warned the virus may transmit via airborne droplets. She advised caution to people living with patients and medical workers who come into contact with patients.