With more than 643 cases of monkeypox in dozens of countries where the virus is not endemic, “the sudden emergence of monkeypox in many countries at the same time suggests that undetected transmission may have been going on for a long time,” he said the Director-General of the World Health Organization Tedros Adhanom Ghebreyesus announced on Wednesday.
In this research, genetic sequences showed that the first cases of monkeypox in 2022 descended from an outbreak that resulted in cases in Singapore, Israel, Nigeria and the United Kingdom in 2017-2019.
Michael Worobey, an evolutionary biologist and professor at the University of Arizona who was not involved in the research, said this suggests “this outbreak has been going on locally for a long time,” like where the virus is endemic. And it means the world has failed to protect those in resource-constrained areas where it was endemic and control it at its source before it spreads globally, he added.
“It’s really a two-eruption story,” Worobey said. “We need to actually turn our attention to where it’s spread … and start caring about that population as much as we do about what’s going on in all these other countries around the world.”
If research continues to show that the virus has spread more widely among humans than previously thought — that is, farther from an animal source — Worobey said a “really good question” is why the world wouldn’t believe monkeypox was endemic can be in places beyond West and Central Africa?
“We don’t even know how long this has been going on”
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 wider implications for global health.
The recent monkeypox outbreak is proving difficult to predict in part because we have not been able to fully trace its origins.
“We don’t even know how long this has been spreading,” Rimoin said. “That could have spread quietly for a while.
“It’s like we’ve now decided to watch a new series, but we don’t know exactly which episode we ended up on. I mean are we in episode two or are we in it Episode four, or are we on episode 10? And how many episodes does this series have? We do not know it.”
Previous cases of monkeypox in humans have not been considered too remote from initial exposure to an infected animal—typically rodents. Once the virus circulates among these animals, it can further bounce back to humans, who might come into contact with infected squirrels or guinea pigs, for example.
If we continue to see sustained human-to-human transmission in this outbreak, even at low levels, it will bring back the possibility of spillover Animals in non-endemic countries from “an existential threat to a definite possibility,” Rimoin told CNN. Such spread could then result in the virus remaining in one environment, hopping back and forth between animals and humans over time.
“We know quite a lot about this virus, but we don’t know everything about this virus,” she said. “We will have to study this very carefully.”
Too early to tell
WHO officials say the global public health risk is moderate.
In a news conference last week, an official at the US Centers for Disease Control and Prevention said it was “too early to say” whether the virus could become endemic in the United States, but experts were “hopeful” that this will not happen.
“I think we’re still at the very beginning of our investigation,” said Dr. Jennifer McQuiston, associate director of the CDC Division of Pathogens and Serious Consequence Pathology.
“We hope that we can contain this in a similar way,” McQuiston said.
According to the European agency, “The likelihood of this spillover event is very low.”
“It was seeded in mosquito populations and … bird populations and was able to become established,” Adalja said.
Still, he agrees that monkeypox is far from inevitable because “2003 was a good opportunity for it” — and it wasn’t.
Worobey says there are too many unknowns to know 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 make blanket assurances.”
A different landscape
It’s not just the murky beginnings and silent spread that make this monkeypox outbreak difficult to predict.
“It’s just a very different epidemiological landscape,” Rimoin added.
“What we know about monkeypox comes largely from studies in very remote rural communities in central Africa, where transmission dynamics are bound to be very different,” she said, particularly when compared to “resource areas in Europe or the US.”
And while a full-fledged pandemic isn’t a cause for concern just yet, that doesn’t mean certain groups aren’t at risk, a WHO official said Monday.
“Right now we’re not worried about a global pandemic,” said Rosamund Lewis, technical director for monkeypox at the WHO Public Health Emergencies Programme.
“However, we are concerned that individuals may acquire this infection through high-risk exposure if they do not have the information they need to protect themselves,” she said. “And we worry that the virus may try to carve out a niche and spread more easily between people, since the world’s population hasn’t been immune to orthopoxviruses since smallpox eradication ended.”
“What we’re seeing now started as a small cluster of cases, and then the investigation quickly led to the discovery of infections in a group of men who have sex with men… and so we don’t yet know where the cause of the actual outbreak came from.” is,” Lewis said on Tuesday.
“The most important thing now is not to stigmatize,” she said.
A number of other unanswered questions could also change our understanding of how well the virus spreads from person to person. For example, it’s unclear how much the virus spreads when people have minimal symptoms, or what impact mutations can have on the virus.
In these points, said Adalja, there is still no reason to worry.
For one, the fact that doctors are seeing a number of cases with lesions in the groin — compared to more common areas like the face, hands and feet — suggests that close contact with symptomatic people with skin lesions is more likely to drive spread, he said Adalia.
And while it’s important to eliminate all of the viral mutations we see in monkeypox, this virus mutates relatively slowly because its genome is made up of double-stranded DNA, which is more stable than, say, the single-stranded RNA of coronaviruses.
The pace of these mutations appears to have accelerated somewhat, Worobey said of the early Edinburgh research. However, the global outbreak likely has a lot more to do with the virus gaining access to new circles where it’s easily transmitted, rather than “the relatively small number of mutations that have accumulated since 2017,” he added .
When it comes to whether the virus is currently changing in any significant way, “we don’t have an answer. We don’t really know,” Lewis said last week.
“We still have no evidence that the virus itself has mutated. We’re starting to gather that information,” she said. “We will convene our groups of virologists and other experts who will discuss this very question based on the sequence of the genome of some of the detected cases.”
Meanwhile, health officials around the world continue to follow cases and the contacts of those cases to better understand how the virus spreads – and how to stop it.
“Right now,” Rimoin said, “we must do everything we can to stop community transmission.”
CNN’s Arnaud Siad and Emmet Lyons contributed to this report.