Cases of this smallpox-related illness had previously only been seen in people with links to West and Central Africa.
However, in the past week Britain, Spain, Portugal, Italy, the United States, Sweden and Canada all reported infections, particularly among young men who had never traveled in Africa before.
France, Germany, Belgium and Australia confirmed their first cases today.
“I am stunned by this. Every day I wake up and there are more countries infected,” said Oyewale Tomori, a virologist at the Nigerian Academy of Sciences and a member of several World Health Organization (WHO) advisory boards.
“It’s not the kind of spread we’ve seen in West Africa, so there could be something new happening in the West,” he said.
To date, no virus-related deaths have been recorded. Monkeypox usually causes fever, chills, rashes, and sores on the face or genitals.
The WHO estimates the disease is fatal for one in 10 people, but smallpox vaccines are protective and some antiviral drugs are in development.
British health authorities are investigating whether the disease is sexually transmitted. Health officials urged doctors and nurses to be on alert for potential cases, but said the risk to the general population was low.
The European Center for Disease Control and Prevention (ECDC) has recommended that all suspected cases be isolated and that smallpox vaccines be offered to high-risk contacts.
Nigeria reports around 3,000 cases of monkeypox a year, according to the WHO. Outbreaks usually occur in rural areas when people come into close contact with infected rats or squirrels, Tomori said.
Ifedayo Adetifa, head of the country’s Center for Disease Control, said none of the Nigerian contacts of the UK patients had developed symptoms and investigations were continuing.
WHO director for Europe Hans Kluge called the outbreak ‘atypical’, saying the outbreak of the disease in so many countries on the continent suggests ‘transmission has been going on for some time’ . He also mentioned that most European cases are mild.
The UK Health Security Agency today reported 11 new cases of monkeypox, saying a “remarkable proportion” of the most recent infections in the UK and Europe have been in young men with no travel history to Africa, who were gay, bisexual or had sex with men.
Authorities in Spain and Portugal also said their cases had been reported in young men who had mostly had sex with other men, adding that these cases had been detected when men presented with lesions in sexual health clinics.
Experts have stressed that they do not know whether the disease is transmitted through sex or through other close sex-related contacts.
Nigeria has not recorded sexual transmission, Tomori said, but noted that some viruses that were not initially known to be sexually transmitted, such as Ebola, were later identified with this form of transmission after Larger epidemics have shown different patterns of spread.
The same could be true for monkeypox, Tomori said.
In Germany, Health Minister Karl Lauterbach said the government was confident the outbreak could be contained, revealing the virus was being sequenced to see if there were any genetic changes that could have made it more infectious .
Rolf Gustafson, professor of infectious diseases, told Swedish broadcaster SVT it was “very difficult” to imagine the situation could get worse.
“We will definitely find a few more cases in Sweden, but I don’t think there will be an outbreak at all,” Gustafson said. “Nothing suggests it at this stage.”
Scientists have said that while it is possible that the first patient in the outbreak contracted the disease in Africa, what is happening now is exceptional.
“We have never seen anything like this happening in Europe,” said Christian Happi, director of the African Center of Excellence in Genomics of Infectious Diseases.
“We haven’t seen anything to suggest that monkeypox transmission patterns have changed in Africa. So if something different is happening in Europe, then Europe has to look at it.
Happi also pointed out that the suspension of smallpox vaccination campaigns after the disease was eradicated in 1980 could inadvertently contribute to the spread of monkeypox.
Smallpox vaccines also protect against monkeypox, but mass vaccination has been suspended for decades.
Portugal has recorded 23 cases of infection with the Monkeypox virus according to the Directorate General of Health (DGS), which is awaiting results for other samples.