Denmark and Scotland on Monday registered their first cases of monkeypox.
Cases in England more than doubled on Monday to 56, prompting UK health authorities to advise close contacts to isolate for up to three weeks.
The World Health Organization is tracking more than 100 confirmed or suspected cases of monkeypox in at least 12 non-African countries.
Scientists try to grapple with how monkeypox outbreaks have traveled outside African borders, all the way to Europe and North America.
"We've seen a few cases in Europe over the last five years, just in travelers, but this is the first time we're seeing cases across many countries at the same time in people who have not travelled to the to the endemic regions in Africa."
The leading theory behind the transnational spread is suggested by Doctor David Heymann, advisor to the World Health Organization.
He told The Associated Press that the outbreaks may have started from sexual transmissions at raves in Spain and Belgium.
"Many diseases can be spread through sexual contact. You can get a cough or a cold through sexual contact, but it doesn't mean that it's a sexually transmitted disease."
Experts say that monkeypox is unlikely to develop into another COVID-19 scare.
They also say that there is very little to suggest that monkeypox has mutated.
"We should say that most of the people who have been identified so far have had more mild disease, or let's say, not severe disease, And the thing I just want to say here is that this is a containable situation."
Smallpox vaccines are 85 percent effective in preventing monkeypox.
Several countries have started stockpiling them in preparation for new outbreaks.
South Korea as of now has enough vaccines for more than 35 million people- almost 70 percent of the population.
Kim Yeon-seung, Arirang News.