More than 18,000 people have contracted monkeypox across 78 countries, new figures show, as scientists advising the World Health Organisation say the window is closing to stop the spread of the virus.
Cases are doubling every two weeks, raising concerns that it will take several months for the outbreak to peak.
WHO Europe has forecast just over 27,000 monkeypox cases in 88 countries by August 2.
The WHO had registered over 18,000 cases in the current outbreak by Thursday morning (Australian time).
More than 70 per cent of cases reported were in Europe and 25 per cent across America.
In Australia, 44 people are being treated for monkeypox. That figure includes 24 in New South Wales, 16 in Victoria, two in the Australian Capital Territory, one in Queensland and one in South Australia.
Five people have died in Africa, and globally around one in 10 patients has required hospitalisation.
WHO Director-General Dr Tedros Ghebreyesus said the majority of cases had occurred as a result of sexual contact between men but that the virus also spread through close contact between people living together and sharing items such as towels.
He called on male partners to take additional precautions.
“For men who have sex with men, this includes, for the moment, reducing your number of sexual partners, reconsidering sex with new partners, and exchanging contact details with any new partners to enable follow-up if needed,” Dr Tedros said.
“The focus for all countries must be engaging and empowering communities of men who have sex with men to reduce the risk of infection and onward transmission, to provide care for those infected, and to safeguard human rights and dignity.
“Stigma and discrimination can be as dangerous as any virus, and can fuel the outbreak.”
Scientists around the world told Reuters there was likely to be sustained transmission for several months and possibly longer.
“We have to get in front of this,” said Anne Rimoin, an epidemiology professor at the University of California, Los Angeles.
“It’s clear the window of opportunity for doing so is closing,” added Dr Rimoin, a member of the WHO expert committee on monkeypox that met last week to determine whether the outbreak constituted a global health emergency.
A majority of committee members voted against the move and, in an unprecedented step, Dr Tedros declared an emergency anyway.
Action stemming from that declaration needed to be urgent, including increased vaccination, testing, isolation for those infected and contact tracing, global health experts said.
“Transmission is clearly unchecked,” said Antoine Flahault, director of the Institute of Global Health at the University of Geneva, who chairs the WHO Europe advisory group.
Jimmy Whitworth, a professor at the London School of Hygiene and Tropical Medicine, said he expected that cases would not plateau for at least the next four to six months, or until the those at highest risk of infection have been either vaccinated or infected.
Monkeypox has been a globally neglected public health problem in parts of Africa for decades, but in May cases began to be reported outside countries where it is endemic.
“The alarm bell was going off [in Africa] but we kept hitting the snooze button. Now it’s time to wake up and do something about it,” Dr Rimoin said.
“An infection anywhere is potentially an infection everywhere.”
On Tuesday, German scientists released a study ahead of peer review that found mutations in one of the 47 cases they sequenced that could help monkeypox spread in people more easily.
One smallpox vaccine, called MVA-BN, has been approved in Canada, the European Union and the US for use against monkeypox.
Two other vaccines, LC16 and ACAM2000, are also being considered.
There are about 16 million doses of MVA-BN globally. The WHO said most are in bulk form, meaning they will take several months to “fill and finish” into vials that are ready to use.
“We still lack data on the effectiveness of vaccines for monkeypox, or how many doses might be needed,” Dr Ghebreyesus said.
“That’s why we urge all countries that are using vaccines to collect and share critical data on their effectiveness.
“It’s important to emphasise that vaccination will not give instant protection against infection or disease, and can take several weeks.”