Belgium has become the first country to introduce a compulsory quarantine for people diagnosed with monkeypox, as the disease continues to spread seemingly randomly across the globe.

Belgian health authorities said that if they are diagnosed with monkeypox, Belgian residents will be required to self-isolate for 21 days, the Daily Mail reported.

Belgium recorded its first infection of monkeypox this past Friday, and it is believed that all subsequent cases are connected to a festival that was held in the port city of Antwerp.

The Belgian quarantine policy comes as European doctors have warned that Great Britain is facing a “significant” rise in monkeypox infections and that the British government’s response is “critical” in containing the spread.

This past weekend, 11 British residents tested positive for the virus, bringing the country’s total up to 20. The infected include a child who is currently in critical condition in a London hospital.

There are currently 100 recorded infections in Europe.

Suggesting that the disease might be spreading through sexual transmission, Dr. Claire Dewsnap, the president of the British Association for Sexual Health and HIV, said that the recent monkeypox outbreak could have a “massive impact” on access to sexual health services in the United Kingdom.

Dr. Susan Hopkins, a chief medical adviser to the U.K. Health Security Agency, also warned that monkeypox is spreading through community transmission.

Dewsnap recently said that “[Britain’s] response is really critical here. There is going to be more diagnoses over the next week.”

She said, “How many is hard to say. What worries me the most is there are infections across Europe, so this has already spread. It’s already circulating in the general population. Getting on top of all those people’s contacts is a massive job.”

Dewsnap suggested that case numbers could greatly increase in the coming weeks. She said, “It could be really significant numbers over the next two or three weeks.”

President Joe Biden is also concerned about the growing case numbers of monkeypox.

This past weekend, just before he left South Korea, Biden said, “Everybody should be concerned about it.”

He said, “We’re working on it, hard to figure out what we do.”