By Aria Bendix —
NBC News
In a matter of weeks, some 80 new cases of monkeypox have been reported in eight European countries, an unprecedented outbreak of a disease that rarely spreads outside central and western Africa.
Other cases have been reported since Wednesday in the United States, Canada and Australia.
The growing number of cases has raised questions about the nature of monkeypox transmission among disease experts, as
many of the patients have no history of travel to Africa,
or known exposure to an infected person.
[Second case of monkeypox detected in the United States]
"How they initially got infected and why it's all over the place remains a mystery," said Dr. Stuart Isaacs, an associate professor of medicine at the University of Pennsylvania.
First case of monkeypox detected in the US: What are the symptoms and how is it transmitted?
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Monkeypox does not jump easily from one person to another.
Until now, most infections occurred among people who had been exposed to an infected animal through bites, scratches or the preparation of wild game meat, experts said.
The most notable outbreak in the Western Hemisphere occurred in 2003, when prairie dogs infected 47 people who kept them as pets in the United States.
[Should we worry about monkeypox? The US registers a case and in Europe they prepare vaccines while the outbreak grows]
From previous cases of human-to-human transmission, scientists have learned that the
virus spreads through the exchange of large respiratory droplets
or through direct contact with body fluids, lesions that form during infection, or contaminated items such as clothing. or the sheets.
Monkeypox
is not considered a sexually transmitted infection,
but it could be spread during sexual encounters, experts say.
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Many of the recent cases in Europe are among men who have sex with men, and a Friday alert from the Centers for Disease Control and Prevention (CDC) suggested that some recent cases began with injuries around the anus and genitals.
"My guess is that sexual transmission will be high on the list of possible culprits," said Dr. Grant McFadden, director of the Center for Immunotherapy, Vaccines and Virotherapy at Arizona State University.
McFadden, Isaacs and several other experts offered their first insights into how and why the new outbreak has grown.
A case of monkeypox in a patient's hand on June 5, 2003.Getty Images
Sexual activity in a close-knit community
McFadden said the genetic sequence of the monkeypox virus that has infected people in Europe appears relatively common.
That's a clue that
human behavior,
rather than changes inherent in the virus itself, could be driving the new cases.
"It could just be a simple accidental chain, for example, in the gay community," McFadden said.
Viruses tend to spread more easily in close-knit groups of people.
According to Global.health, a group that compiles data on infectious diseases, all recent monkeypox cases reported by gender have been male.
“You could imagine that one person would have it, and if they were part of a small, intimate group of people, they could have spread it between those connections,” said Dr. David Evans, a virologist at the University of Alberta.
But that doesn't explain why the cases are so
geographically dispersed.
And the experts also agreed that it's premature to suggest that monkeypox is spreading solely within a community.
It will be important to locate the first case of human-to-human transmission and study it, they said, to determine how the outbreak started.
Some experts hypothesize that the relaxation of
international
travel
restrictions
may have contributed to the spread.
“It seems like the virus has always had this potential capacity” for human-to-human transmission, McFadden said.
“Just that in the past it never got a chance, or if it did, it quickly died out and we never really saw it as an event.
Instead, now that people can travel around the world, we may very well see it for the first time in a larger context,” he added.
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People may be more susceptible to monkeypox now than in the past
Most people who get monkeypox recover completely.
In the past, only 1% of people who have contracted the West African strain responsible for the new outbreak have died.
But a different lineage of the virus has killed about 10%, according to the World Health Organization (WHO).
Monkeypox belongs to the poxvirus family, which includes smallpox.
Smallpox vaccines are about 85% effective in preventing monkeypox, according to the WHO.
But the United States stopped vaccinating the public against smallpox in 1972, and worldwide vaccination ceased around 1980, when the disease was eradicated worldwide.
Therefore, people have
less immunity
to poxviruses in general than in past decades.
"We no longer have immunity, and so we're going to continue to see cases emerge, and more of them over time," said Anne Rimoin, a professor of epidemiology at the University of California, Los Angeles, Fielding School of Public Health.
Isaac said declining population immunity could also explain why Africa has seen more cases of monkeypox in recent years.
The Democratic Republic of the Congo reported up to 18,000 confirmed or suspected cases of monkeypox between 2010 and 2019, but fewer than 10,000 between 2000 and 2009. In 2020 alone, the country reported more than 6,000 suspected cases, according to the WHO.
This 2003 microscope image provided by the CDC shows monkeypox.
AP
Doctors may have ignored some of the early cases
Monkeypox may have started spreading in Europe before it reached scientists' radars, several experts suggest.
"Because of the geographical spread of cases in Europe and beyond, this suggests that transmission may have been ongoing for some time," said Dr Hans Kluge, WHO regional director for Europe.
Isaacs said doctors can sometimes miss a case of monkeypox because the rash looks like chickenpox, syphilis or herpes.
"Most doctors and clinics don't think about monkeypox," he said.
"It may have been brewing over time and just no one has thought to identify or think about this," he added.
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That's especially likely if a patient has mild disease, McFadden said.
So far, that has been the case for most new infections, according to reports from the United States, Belgium, Canada, Germany and Portugal.
No recent deaths have been reported.
"If it was particularly mild, someone may not have noticed much and thought much about what was going on and then spread it among their social group," Evans said.