A "sexual form of monkeypox" is being blamed for the global spread of the virus, with outbreaks now linked to an adult sauna and fetish festival.
The World Health Organisation (WHO) suggested human-to-human transmission is occurring between people who are in "close physical contact" with cases who are symptomatic, with officials also investigating a number of cases that have been linked to the gay community.
"Based on currently available information, cases have mainly but not exclusively been identified among men who have sex with men (MSM) seeking care in primary care and sexual health clinics," WHO said.
An adult sauna in Spain has been linked to many of the monkeypox cases that have emerged in the city of Madrid.
The Paraiso sauna, a gay-friendly establishment in the heart of the city, revealed on Twitter that it was temporarily closing.
"The Paraiso sauna will remain closed for the next few days, a precautionary measure in the face of the alert … over the emergence of so-called monkeypox infections in the Madrid region," it said.
Enrique Ruiz Escudero, a health official for the Madrid region, told reporters authorities had recorded 21 confirmed cases and 19 suspected cases.
"Most people who tested positive have a link to this source," he said, referring to the sauna.
"The Public Health Department will carry out an even more detailed analysis … to control contagion, cut the chains of transmission and try to mitigate the transmission of this virus as much as possible."
Three confirmed cases in Belgium have also been linked to a large-scale fetish festival in the city of Antwerp.
Darklands Festival is a four-day event which encourages visitors to "explore their sexuality and develop a safe and sane interest for the many fetishes in our community".
"The various tribes in the gay fetish community (leather, rubber, army, skinhead, puppies …) come together to create a unique spectacle of fetish brotherhood," the website says.
Organisers of the event recently issued a warning to attendees that the three monkeypox cases officially identified in Belgium have been linked to visitors at the festival.
"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," the organisers said in a statement.
"The Risk Assessment Group of the federal government has asked Darklands to inform it's guest about these infections."
As of Saturday, there have been 92 laboratory confirmed cases of the virus globally, along with 28 suspected cases.
These numbers are continuing to grow, with cases already confirmed in 12 countries, including two cases in Australia.
Monkeypox is not usually fatal but often manifests itself through fever, muscle aches, swollen lymph nodes, chills, exhaustion and a chickenpox-like rash on the hands and face.
The virus, which is endemic in parts of Africa, can be transmitted through contact with skin lesions or droplets of bodily fluid from an infected person.
However, WHO official David Heymann, said what appears to be happening now is the virus is being sexually transmitted, causing fresh outbreaks globally.
"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 infectious disease specialist told Reuters.
One of Australia's cases was detected in a man in his 40s who recently returned to Sydney from Europe.
He went to his GP several days after arriving back in Australia, with the doctor determining his symptoms were compatible with monkeypox, resulting in urgent testing.
The other case is a man in his 30s who developed mild symptoms before returning to Melbourne from London on May 16.
He remains in isolation at the Alfred Hospital with mild symptoms.
There is no specific treatment but vaccination against smallpox has been found to be about 85 per cent effective in preventing monkeypox.
The symptoms usually last between two to four weeks.
NSW chief health officer Dr Kerry Chant said the virus should not be cause for panic.
"Usually, you need to have quite prolonged face-to-face contact," Dr Chant said.
"It is not the same spread mechanism as Covid or the flu, where it [transmission] is more fleeting."
However, she did urge people to be vigilant about the symptoms and seek medical care if any symptoms emerge.
"It starts off with fever, muscle aches and pains. You can get those in large lymph nodes, headaches, feeling tired and lethargic," Dr Chant said.
"And then it can be followed by a rash one to three days longer. Often the rash starts on the face."