Monkeypox infections have historically only been recorded among people with links to central and West Africa. But in the past few weeks, countries including the UK, the US, Spain, Portugal, Italy, Sweden and Canada have recorded cases, mostly in young men who hadn’t previously travelled to Africa.
According to the most recent figures from the World Health Organisation (WHO), there are about 80 confirmed cases worldwide and 50 more suspected.
Virologist Oyewale Tomori, former head of the Nigerian Academy of Science, told The Associated Press: “I’m stunned by this. Every day I wake up and there are more countries infected.”
Tomori, who sits on several WHO advisory boards, added: “This is not the kind of spread we’ve seen in West Africa, so there may be something new happening in the West.”
Typical symptoms of monkeypox include fever, headache, muscle aches, backache, swollen lymph nodes, chills and exhaustion.
As yet, no one has died in the outbreak, but the WHO estimates the disease is fatal for up to one in 10 people.
The European Center for Disease Control and Prevention has recommended all suspected cases be isolated and that high-risk contacts be offered smallpox vaccine.
According to the WHO, about 3,000 monkeypox cases are recorded in Nigeria each year.
Outbreaks are usually in rural areas, when people have close contact with infected rats and squirrels, Tomori said, but added many cases are likely missed.
On Friday, eleven more cases of monkeypox were identified in England by the UK Health Security Agency (UKHSA). The latest infections bring the total number of cases confirmed in England since 6 May to 20.
Dr Susan Hopkins, chief medical adviser at the UKHSA, said: “We anticipated that further cases would be detected through our active case finding with NHS services and heightened vigilance among healthcare professionals.
“We expect this increase to continue in the coming days and for more cases to be identified in the wider community. Alongside this we are receiving reports of further cases being identified in other countries globally.
“We continue to rapidly investigate the source of these infections and raise awareness among healthcare professionals. We are contacting any identified close contacts of the cases to provide health information and advice.”
She said a notable proportion of recent cases in the UK and Europe have been found in gay and bisexual men, and encouraged them to be particularly “alert to the symptoms and seek help if concerned”. Health officials in Spain and Portugal also said their cases were in young men who mostly had sex with other men.
Dr Hopkins’ comments come as health officials in the UK explore whether the virus is being sexually transmitted, but experts have stressed they do not know if the disease is being spread through sex or other close contact related to sex.
Tomori told the AP that, despite Nigeria not having seen sexual transmission, viruses that hadn’t initially been known to transmit via sex, such as Ebola, were later proven to do so after bigger epidemics showed different patterns of spread.
He said the same could be true of monkeypox.
Meanwhile, Germany’s health minister Karl Lauterbach announced that Berlin was confident the outbreak could be contained.
He said the virus was undergoing sequencing to see if there were any genetic changes that might have made it more infectious.
Elsewhere, Rolf Gustafson, an infectious diseases expert, told Swedish broadcaster SVT that it was “very difficult” to imagine the outbreak become inflamed.
“We will certainly find some further cases in Sweden, but I do not think there will be an epidemic in any way,” he said, adding: “There is nothing to suggest that at present.”
Christian Happi, director of the African Centre of Excellence for Genomics of Infectious Diseases, said: “We’ve never seen anything like what’s happening in Europe.
“We haven’t seen anything to say that the transmission patterns of monkeypox have been changing in Africa. So if something different is happening in Europe, then Europe needs to investigate that.”
He also said that the suspension of smallpox vaccination campaigns - which also protects against monkeypox - after the disease was eradicated in 1980 might inadvertently be helping monkeypox spread.
Happi said: “Aside from people in west and Central Africa who may have some immunity to monkeypox from past exposure, not having any smallpox vaccination means nobody has any kind of immunity to monkeypox.”
His remarks come as health officials in South Africa call for an investigation into the European outbreak to determine those first infected with monkeypox.
Shabir Mahdi, a professor of vaccinology at the University of Witwatersrand in Johannesburg, said: “We need to really understand how this first started and why the virus is now gaining traction.
“In Africa, there have been very controlled and infrequent outbreaks of monkeypox. If that’s now changing, we really need to understand why.”