“We know that monkeypox can spread if there is close contact with an infected person’s wounds, and it seems that sexual contact has now widened that infection,” Hayman said.
This marks a significant departure from the general pattern of disease outbreaks in Central and West Africa, where humans are primarily infected by animals such as wild rats and primates, and its prevalence has not spread across borders.
To date, the WHO has recorded more than 90 cases of monkeypox in a dozen countries, including Britain, Spain, Israel, France, Switzerland, the United States and Australia.
A senior health official in Madrid said on Monday that the Spanish capital had so far recorded 30 confirmed cases. Enrique Ruiz Escudero says authorities are investigating possible links to a recent gay pride event in the Canary Islands, which drew about 80,000 people and sued a Madrid senator.
Hyman presided over an emergency meeting of the WHO’s advisory group on the threat of infectious diseases on Friday to assess the ongoing epidemic and said there was no evidence that monkeypox could transform into a more contagious form.
Monkeypox usually causes fever, chills, rash and sores on the mouth or genitals. It can be spread through close contact with an infected person or their clothing or bed sheets, but sexually transmitted infections have not yet been documented. Most people recover from the disease within a few weeks without the need for hospitalization. The smallpox vaccine, a related disease, is also effective in preventing monkeypox and some antiviral drugs are being developed.
In recent years, up to 6% of infections have been fatal, but no deaths have been reported so far. The WHO said the confirmed cases still appear to be linked to the less serious West African monkeypox virus group and a virus that was first detected in 2018-2019 in exports from Nigeria to Britain, Israel and Singapore.
The UN agency called the outbreak an “extremely unusual phenomenon” and said cases were being reported in several different countries, indicating that the disease had been silent for some time. The agency’s Europe director warned that with the onset of summer across the continent, mass gatherings, festivals and parties could accelerate the spread of monkeypox.
Other scientists have suggested that it would be difficult to resolve in itself the sexual or intimate contact that has led to the recent spread of monkeypox across Europe.
Mike Skinner, a virologist at Imperial College London, said: “Naturally, sexual activity involves intimate contact, which is expected to increase the likelihood of infection regardless of a person’s sexual orientation and mode of transmission.”
On Sunday, Dr Susan Hopkins, chief medical adviser to Britain’s health safety agency, said she hoped more monkeypox cases would be detected in the country “on a daily basis”.
UK officials say a “significant proportion” of young people in Britain and Europe have no history of traveling to Africa and are homosexual, bisexual or have sex with men. Authorities in Portugal and Spain also said their cases were among men who had sex with other men mostly and whose sexually transmitted infections increased when they sought help for injuries at health clinics.
Heyman, a professor of infectious diseases at the London School of Hygiene and Tropical Medicine, said the outbreak of monkeypox was probably a random event that could be detected for a single infection.
“It is very possible that someone became infected, developed a lesion on the genitals, hands or elsewhere and then spread it to others during sexual or intimate, physical contact,” Heyman speculated. “And then there were the international events that sowed the seeds of the outbreak in the United States and other European countries around the world.”
He emphasized that the disease was less likely to spread widely.
“It’s not cowardly,” he said. “We need to slow it down, but it doesn’t spread in the air and we have the vaccine to protect against it.” Heiman said research should be conducted quickly to determine whether monkeys can be spread by humans without symptoms and whether the population at risk should take precautions to protect themselves.
Barry Hatton of Lisbon contributed to this report.