Health officials in Spain have linked many of the country's 30 monkeypox cases to a single adult sauna in Madrid, the Telegraph reported.

On Friday, Enrique Ruiz Escudero, the region’s cabinet minister for health of the community, said that the cases were linked to an event held at the sauna. That sauna was a place where gay men went seeking intimate relations, the Daily Mail added.

In the UK as well, health officials have noted that a "notable proportion" of cases are in gay and bisexual men.

In Belgium, three cases have been linked to a large-scale "fetish festival" in Antwerp, organizers said. According to the Telegraph, the Darklands Festival warned those who attended four days of parties that authorities had linked the festival to Belgium's three confirmed cases.

On its website, the festival added that, "There’s reason to assume that the virus has been brought in by visitors from abroad to the festival after recent cases in other countries."

Sources also told the Telegraph that an internationally-advertised gay party in Spain is also being investigated as the root of the global monkeypox outbreak.

Monkeypox is generally not considered a virus that spreads among humans, and this is the first time sustained human-to-human transmission has been seen outside Africa.