Two more European countries reported unusual monkeypox cases on Wednesday, a development that suggests an outbreak first spotted in the United Kingdom is more widespread than first believed.
The news of cases in additional countries led a senior official of the Centers for Disease Control and Prevention to warn that cases will likely be spotted in the United States.
“I think we have concerns there might be cases in the United States. I don’t know that we have strong visibility on people who might be reporting for what seem to be a minor rash illness to an STI clinic or something like that,” said Jennifer McQuiston, deputy director of the CDC’s division of high consequence pathogens and pathology.
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“Given that we have seen now confirmed cases out of Portugal, suspected cases out of Spain, we’re seeing this expansion of confirmed and suspect cases globally, we have a sense that no one has their arms around this to know how large and expansive it might be. And given how much travel there is between the United States and Europe, I am very confident we’re going to see cases in the United States,” McQuiston told STAT in an interview.
Spain announced that it was investigating eight suspected cases, and Portugal said it was investigating more than 20 suspected cases, five of which have already been confirmed. It is not currently clear if the outbreaks are linked to each other or to the one in the U.K., where nine confirmed and one probable case have been reported.
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If they are connected, it is not yet clear if the virus spread from the U.K. to Europe, or the reverse. Nor is it known how long the virus has been spreading in these countries.
Some of the cases have been detected in men who have sex with men, which raises the possibility that there may be more spread than has currently been detected, said Michael Osterholm, director of the University of Minnesota’s Center for Infectious Diseases Research and Policy.
“There could be dynamic transmission here that we just haven’t appreciated because of the potential number of contacts,” he said.
Tom Inglesby, director of the Center for Health Security at the Johns Hopkins Bloomberg School of Public Health, said a number of countries outside Central and West Africa, where monkeypox is more common, have experience coping with introductions of the virus, so there is a possibility that the outbreaks will be “relatively small.”
“I think that’s still probable, given the past,” Inglesby told STAT. “But on the other hand, this is starting off with much more of a foothold, in a much more distributed way, and we don’t understand how it got … into those networks.”
“This could have the potential to move around and is going to require pretty strong public education efforts in affected communities and maybe even more broadly, so that people recognize the possibility” of monkeypox infection, he said.
The U.K. Health Security Agency announced Wednesday that it had detected two additional cases, bringing to nine the number reported there this month. Prior to this outbreak the U.K. had only ever detected seven monkeypox cases. The two latest cases had not traveled to the countries where monkeypox virus is endemic, and have no known links to any of the prior cases “so it is possible they acquired the infection through community transmission,” the agency said in a statement, adding that recent cases have been predominantly among men who identify as gay, bisexual, or who have sex with men.
It appears that in at least some of the European cases, the same dynamic may be at play. Spain’s ministry of health reported that the eight suspected cases there had been detected by a sexual health clinic in Madrid, according to news reports.
Portuguese authorities did not reveal how the cases there had been detected, but said they were all men and most were young.
The quick accumulation of cases is ringing alarm bells.
On Tuesday, the CDC signaled it was worried about the state of the outbreak in the U.K. and the potential that cases would be found in other countries.
“We do have a level of concern that this is very different than what we typically think of from monkeypox,” said McQuiston.
“We don’t understand how many other cases could be out there in the U.K., for example, with undefined chains of transmission. We have a sense that there might be some unusual methods of transmission, through intimate contact or some form of close personal contact that we’ve not previously associated with monkeypox. And I think there’s a lot of travel between the U.K. and the United States and other global areas,” she said in an interview.
The World Health Organization also signaled its concern, saying that a shift in the epidemiology of the disease in countries where the virus is endemic that has occurred in recent years needs to be investigated.
“We’re seeing a shift in the age distribution of cases. We’re seeing a shift in the geographic distribution of cases,” said Michael Ryan, executive director of the WHO’s Health Emergencies Program.
“We have to really understand that deep ecology. We have to really understand human behavior in those regions and we have to try to prevent the disease from reaching humans in the first place.”
The monkeypox virus is related to the variola virus, which caused smallpox, a once dreaded disease that was declared eradicated in 1980. The symptoms of monkeypox are similar to but milder than smallpox.
Infected people develop flu-like symptoms — fever, body aches, chills — but also swollen lymph nodes. With one to three days of the onset of fever, a distinctive rash appears, often starting on the face. Many conditions can cause rashes but the monkeypox rash has some unusual features, notably the fact that vesicles can form on the palms of the hands.
In countries where it is endemic, the virus is believed to mainly spread to people from infected animals when people kill or prepare bushmeat for consumption.
Once the virus jumps to people, human-to-human transmission can occur via respiratory droplets — virus-laced saliva that can infect the mucosal membranes of the eyes, nose, and throat — or by contact with monkeypox lesions or bodily fluids, with the virus entering through small cuts in the skin. It can also be contracted by contact with clothing or linens contaminated with material from monkeypox lesions.
Cases outside of Africa have been rare, though there was a large outbreak in the United States in 2003 that involved 47 confirmed and probable cases in six states. That outbreak, the first reported from outside of Africa, was traced back to the importation of small mammals from Ghana.
However, in the past few years there has been small increases in exported monkeypox cases. The U.S. detected two in 2021, both in travelers who had returned from Nigeria. The U.K. has seen multiple importations in the past few years and Israel and Singapore have also detected cases.
McQuiston said the number of exported cases from Nigeria in particular appear to be at odds with the reported number of cases in the country itself.
“I think that we are concerned about the number of exported cases in travelers we’ve seen. And to have so many of them in the last few years is simply a flag to us that there’s a lot more monkeypox transmission happening in Nigeria than perhaps the [official] numbers would suggest,” she said.
“And I think it also is a flag to us that the more traditional routes of transmission that we think of such as hunting wild animals, contact with bushmeat, living at that interface between the jungle and small communities does not seem to be a driver of transmission in terms of what we see happening. And so that makes us cast a wider net about what risk factors might be.”