A monkeypox outbreak continues to grow in countries where the virus isn’t normally found, putting global health officials on high alert.
Now with more than 643 cases of monkeypox in dozens of countries where the virus is not endemic, “the sudden appearance of monkeypox in many countries at the same time suggests there may have been undetected transmission for some time,” World Health Organization Director-General Tedros Adhanom Ghebreyesus said Wednesday.
The virus has been circulating for decades in some places, including parts of West and Central Africa. In early research posted this week, scientists at the Institute of Evolutionary Biology at the University of Edinburgh described how the genetic pattern they’re seeing suggests that “there has been sustained human to human transmission since at least 2017.”
In that research, genetic sequences showed that the first monkeypox cases in 2022 appear to have descended from an outbreak that resulted in cases in Singapore, Israel, Nigeria and the United Kingdom from 2017 to 2019.
Cynthia S. Goldsmith, Russell Regner/CDC/AP
This 2003 electron microscope image made available by the Centers for Disease Control and Prevention shows mature, oval-shaped monkeypox virions, left, and spherical immature virions, right, obtained from a sample of human skin associated with the 2003 prairie dog outbreak.
Michael Worobey, an evolutionary biologist and professor at the University of Arizona who was not involved in the research, said it suggests that “this outbreak has been going on for a long time, locally,” as in where the virus is endemic. And it means the world has failed to protect those in resource-limited areas where it has been endemic and to control it at its source before it spread globally, he added.
“It’s really a tale of two outbreaks,” Worobey said. “We need to actually turn our attention to where it’s been spreading … and start caring about that population just as much as we care about what’s going on in all these other countries around the world.”
If research continues to show that the virus has spread more among humans than previously thought — more distant from an animal source, that is — Worobey said one “really good question” is: Why wouldn’t the world think monkeypox can be endemic in places beyond West and Central Africa?
‘We don’t even know how long this has been spreading’
Epidemiologist Anne Rimoin has been studying monkeypox for about two decades and has long warned that its spread in places like the Democratic Republic of the Congo could have broader global health implications.
“If monkeypox were to become established in a wildlife reservoir outside Africa, the public health setback would be difficult to reverse,” Rimoin, now a professor of epidemiology at the UCLA Fielding School of Public Health, warned in a 2010 article published in the Proceedings of the National Academy of Sciences.
The latest monkeypox outbreak is proving difficult to predict in part because we haven’t been able to fully trace its origins.
“We don’t even know how long this has been spreading,” Rimoin said. “This could have been spreading silently for a while.
“It’s like we’ve now decided to watch a new series, but we don’t know exactly which episode we’ve landed on. I mean, are we on episode two, or are we onepisode four, or are we on episode 10? And how many episodes are in this series? We don’t know.”
Christine Uyanik/Reuters
Roman Woelfel, head of the Institute of Microbiology of the German Armed Forces, works in his lab in Munich on May 20 after Germany detected its first case of monkeypox.
Previous human cases of monkeypox weren’t thought to be too far removed from some initial exposure to an infected animal — typically rodents. Once the virus is circulating among these animals, it can continue jumping back into humans who might come into contact with infected squirrels or guinea pigs, for example.
If we continue to see sustained person-to-person transmission in this outbreak, even at low levels, that brings the possibility of a spillover back into animals in nonendemic countries from “an existential threat to a distinct possibility,” Rimoin told CNN. Such a spillover could then allow the virus to remain in an environment, jumping between animals and humans over time.
Too early to tell
WHO officials say the global public health risk is moderate.
“The public health risk could become high if this virus exploits the opportunity to establish itself as a human pathogen and spreads to groups at higher risk of severe disease such as young children and immunosuppressed persons,” according to a WHO risk assessment issued Sunday, which added that “immediate action from countries is required to control further spread among groups at risk, prevent spread to the general population and avert the establishment of monkeypox as a clinical condition and public health problem in currently non-endemic countries.”
In a news briefing last week, an official with the U.S. Centers for Disease Control and Prevention said that it’s “too early to tell” whether the virus could become endemic in the United States but that experts remain “hopeful” that won’t happen.
“I think we’re in the very early days of our investigations,” said Dr. Jennifer McQuiston, deputy director of the CDC’s Division of High Consequence Pathogens and Pathology.
McQuiston pointed out that the virus didn’t become endemic after the last monkeypox outbreak in the United States, in 2003, when pet prairie dogs led to dozens of infected people across multiple states.
“We’re hopeful we’ll be able to similarly contain this,” McQuiston said.
The European CDC appeared to agree with McQuiston in its own assessment last week, saying there’s no evidence that the virus established itself in US wildlife after authorities conducted “an aggressive campaign for exposed animals during the 2003 outbreak.”
According to the European agency, “The probability of this spill-over event is very low.”
Still, it wouldn’t be the first virus to take up residence in a U.S. animal population, said Dr. Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security at the Bloomberg School of Public Health. Before 1999, West Nile virus was unheard-of in the U.S. Now, it’s the leading cause of mosquito-borne disease in the country.
“It got seeded into mosquito populations and … bird populations and was able to establish itself,” Adalja said.
Still, he agrees that this is far from an inevitability with monkeypox because “2003 was a good opportunity for it to happen,” and it didn’t.
Worobey says there are too many unknowns to figure out where this monkeypox outbreak is headed.
“What we’re finding out here, in real time, is that we know very little about what’s going on,” he said, “and I think it’s too early to be giving blanket reassurances.”
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Expert: Monkeypox likely spread by sex at 2 raves in Europe
Cynthia S. Goldsmith, Russell Regner/CDC via AP
Monkeypox is a virus that originates in wild animals like rodents and primates, and occasionally jumps to people. Most human cases have been in central and west Africa, where the disease is endemic.
The illness was first identified by scientists in 1958 when there were two outbreaks of a “pox-like” disease in research monkeys — thus the name monkeypox. The first known human infection was in 1970, in a 9-year-old boy in a remote part of Congo.
Cynthia S. Goldsmith, Russell Regner/CDC via AP
Monkeypox is a virus that originates in wild animals like rodents and primates, and occasionally jumps to people. Most human cases have been in central and west Africa, where the disease is endemic.
The illness was first identified by scientists in 1958 when there were two outbreaks of a “pox-like” disease in research monkeys — thus the name monkeypox. The first known human infection was in 1970, in a 9-year-old boy in a remote part of Congo.
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Expert: Monkeypox likely spread by sex at 2 raves in Europe
AP photo/Janet Hostetter
Monkeypox belongs to the same virus family as smallpox but causes milder symptoms.
Most patients experience only fever, body aches, chills and fatigue. People with more serious illness may develop a rash and lesions on the face and hands that can spread to other parts of the body.
The incubation period is from about five days to three weeks. Most people recover within about two to four weeks without needing to be hospitalized.
Monkeypox can be fatal for up to one in 10 people and is thought to be more severe in children.
People exposed to the virus are often given one of several smallpox vaccines, which have been shown to be effective against monkeypox. Anti-viral drugs are also being developed.
On Thursday, the European Centre for Disease Prevention and Control recommended all suspected cases be isolated and that high-risk contacts be offered the smallpox vaccine.
AP photo/Janet Hostetter
Monkeypox belongs to the same virus family as smallpox but causes milder symptoms.
Most patients experience only fever, body aches, chills and fatigue. People with more serious illness may develop a rash and lesions on the face and hands that can spread to other parts of the body.
The incubation period is from about five days to three weeks. Most people recover within about two to four weeks without needing to be hospitalized.
Monkeypox can be fatal for up to one in 10 people and is thought to be more severe in children.
People exposed to the virus are often given one of several smallpox vaccines, which have been shown to be effective against monkeypox. Anti-viral drugs are also being developed.
On Thursday, the European Centre for Disease Prevention and Control recommended all suspected cases be isolated and that high-risk contacts be offered the smallpox vaccine.
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Expert: Monkeypox likely spread by sex at 2 raves in Europe
AP Photo/Anja Niedringhaus, File
The World Health Organization estimates there are thousands of monkeypox infections in about a dozen African countries every year. Most are in Congo, which reports about 6,000 cases annually, and Nigeria, with about 3,000 cases a year.
Patchy health monitoring systems mean many infected people are likely missed, experts say.
Isolated cases of monkeypox are occasionally spotted outside Africa, including in the U.S. and Britain. The cases are typically associated with travel to Africa or contact with animals from areas where the disease is more common.
In 2003, 47 people in six U.S. states had confirmed or probable cases. They caught the virus from pet prairie dogs that been housed near imported small mammals from Ghana.
AP Photo/Anja Niedringhaus, File
The World Health Organization estimates there are thousands of monkeypox infections in about a dozen African countries every year. Most are in Congo, which reports about 6,000 cases annually, and Nigeria, with about 3,000 cases a year.
Patchy health monitoring systems mean many infected people are likely missed, experts say.
Isolated cases of monkeypox are occasionally spotted outside Africa, including in the U.S. and Britain. The cases are typically associated with travel to Africa or contact with animals from areas where the disease is more common.
In 2003, 47 people in six U.S. states had confirmed or probable cases. They caught the virus from pet prairie dogs that been housed near imported small mammals from Ghana.
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Expert: Monkeypox likely spread by sex at 2 raves in Europe
AP Photo/Allen Sullivan
It's the first time monkeypox appears to be spreading among people who didn't travel to Africa.
In Europe, infections have been reported in Britain, Italy, Portugal, Spain and Sweden. Most of the cases involve men who have had sex with men.
Britain's Health Security Agency said its cases are not all connected, suggesting that there are multiple chains of transmission happening.
The infections in Portugal were picked up at a sexual health clinic, where the men sought help for lesions on their genitals.
On Wednesday, U.S. officials reported one case of monkeypox in a man who had recently traveled to Canada, where authorities are investigating potential infections.
AP Photo/Allen Sullivan
It's the first time monkeypox appears to be spreading among people who didn't travel to Africa.
In Europe, infections have been reported in Britain, Italy, Portugal, Spain and Sweden. Most of the cases involve men who have had sex with men.
Britain's Health Security Agency said its cases are not all connected, suggesting that there are multiple chains of transmission happening.
The infections in Portugal were picked up at a sexual health clinic, where the men sought help for lesions on their genitals.
On Wednesday, U.S. officials reported one case of monkeypox in a man who had recently traveled to Canada, where authorities are investigating potential infections.
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Expert: Monkeypox likely spread by sex at 2 raves in Europe
Cynthia S. Goldsmith, Russell Regner/CDC via AP
It's possible, but it's unclear at the moment.
Monkeypox has not previously been documented to have spread through sex, but it can be transmitted through close contact with infected people, their body fluids and their clothing or bedsheets.
Michael Skinner, a virologist at Imperial College London, said it's still too early to determine how the men in the U.K. were infected.
“By nature, sexual activity involves intimate contact, which one would expect to increase the likelihood of transmission, whatever a person’s sexual orientation and irrespective of the mode of transmission," Skinner said.
Francois Balloux of University College London said monkeypox said sex qualifies as the kind of close contact needed to transmit the disease.
The U.K. cases "do not necessarily imply any recent change in the virus’ route of transmission,” Balloux said.
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Barry Hatton in Lisbon, Portugal, contributed to this report.
Cynthia S. Goldsmith, Russell Regner/CDC via AP
It's possible, but it's unclear at the moment.
Monkeypox has not previously been documented to have spread through sex, but it can be transmitted through close contact with infected people, their body fluids and their clothing or bedsheets.
Michael Skinner, a virologist at Imperial College London, said it's still too early to determine how the men in the U.K. were infected.
“By nature, sexual activity involves intimate contact, which one would expect to increase the likelihood of transmission, whatever a person’s sexual orientation and irrespective of the mode of transmission," Skinner said.
Francois Balloux of University College London said monkeypox said sex qualifies as the kind of close contact needed to transmit the disease.
The U.K. cases "do not necessarily imply any recent change in the virus’ route of transmission,” Balloux said.
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Barry Hatton in Lisbon, Portugal, contributed to this report.
