In the summer of 2003, just weeks after a monkeypox outbreak sickened about 70 people in the Midwest, Mark Slifka visited “the superspreader,” he told me, “that infected half of Wisconsin’s cases.”
Chewy, a prairie dog, had succumbed to the disease at the time, which he almost certainly contracted at an exotic animal facility he shared with infected rats in a Ghana pouch. But his owners’ other prairie dog, Monkey — named for the way he clambered through his cage — had contracted the pathogen and survived. “I was a little concerned,” said Slifka, an immunologist at Oregon Health & Science University. All the traits that made Monkey a charismatic pet also made him a contagious threat. He cuddled and nibbled at his owners; when they left the house, he wrapped himself in their clothes until they came back. “It was sweet,” Slifka told me. “But I thought, ‘Can Monkey be in his cage when we come over?'”
Slifka came home without smallpox and the 2003 outbreak was dead. But that torrent of cases was a bull’s eye: an opportunity for the virus to establish itself in a new animal host. One lasting interspecies hop, similar to the one that made SARS-CoV-2 white-tailed deer, and monkeypox will be “with us forever” in the U.S., says Barbara Han, a disease ecologist at the Cary Institute, in New York . York. In central and western Africa, where the virus is endemic, scientists suspect that at least a few rodent species slosh it intermittently into humans. And as the largest monkeypox epidemic ever recorded outside of Africa continues to unfold — more than 2,700 confirmed and suspected cases have been reported in about three dozen countries — the virus is now getting far more shots on target. This time we may not be so lucky; the geography of monkey pox may soon change.
Each new leap could change the future for this virus and for us. Experts consider the possibility unlikely — “low risk, but it’s a risk,” said Jeffrey Doty, a disease ecologist at the CDC. Existing animal reservoirs make it nearly impossible to eradicate some diseases; the emergence of new ones can trigger future outbreaks in places where they are not currently common. If researchers can identify some of those animals and prevent them from mixing with us, we can avoid some of those problems. But that’s a big one if† With so many susceptible animals out there, figuring out which ones harbor the virus could send researchers on a yearlong race, with no clear finish line.
Scientists first discovered monkey pox in the 1950s, in two species of monkeys housed in a Danish animal facility; hence the name, which will probably change soon. But in the decades that followed, rodents in Central and West Africa, including rope weekhorns, solar squirrels, Gambian possums and dormouse, provide the best evidence that the virus is present in animals. All signs point to rodents being “responsible for sustaining this virus in the wild,” Doty told me, which is why he and his colleagues are most concerned about those mammals when they think about which animals live in non-endemic species. areas pose the greatest future risk.
But one lot of rodents rush across the planet – about 2,500 species, which together make up about 40 percent of known mammals. While not all species are capable of carrying monkey pox, for example guinea pigs, golden hamsters, and common mice and rats, many of them can.
Building a case for an animal reservoir often requires years of fieldwork, strict safety protocols, and good luck. For a few viruses, the reservoir story is relatively neat: Hendra virus, an often deadly respiratory infection, usually moves from bats to horses to humans; most hantaviruses, which can cause lethal fever, settle in one rodent species each. However, Monkeypox is much less finicky than that. Experts suspect that several animals are letting the virus seep into the wild. How much, however, is a guess.
The gold standard for establishing a reservoir requires isolating active virus – evidence that the pathogen was xeroxing itself in a viable host. But in nature’s wilderness, “you can break your back and end up with only five animals of a species,” said Han, who uses machine learning to predict potential monkeypox reservoirs. “And what are five animals?” They may not have the virus in question, even if other members of their population do; they may have been caught at an age or during a season when the pathogen is not present. And among the animals harboring the virus, a reservoir may not always be the most obvious: rodents may be among the most commonly detected carriers of monkeypox, but outbreaks in zoos and lab experiments have shown the virus’s ability to infiltrate in anteaters, rabbits, and a sizable handful of primates, along with other non-mouse mammals. In several of these species and others, scientists have found antibodies that recognize poxviruses, indicating previous exposures; they even uncovered the DNA of the virus. Only twice, however, has anyone found an active virus in wild animals: a rope weekhorn from the Democratic Republic of Congo in the 1980s and a sooty-black mangabey found in the Ivory Coast about a decade ago.
Even those cases weren’t slam dunks. More is needed to “figure out which ones are a reservoir, versus which ones get infected, but aren’t really responsible for maintaining the circulation of the virus in humans,” Jamie Lloyd-Smith, a disease ecologist, told IPS. the UCLA. Just because an animal can get the virus to us doesn’t mean it will.
For that to happen, humans must have enough contact with the animals to make exposure likely, for example during routine bushmeat hunts or in broken landscapes where animals forage for food in and around people’s homes. Lloyd-Smith, who surveyed Congo residents, said it’s harder than it sounds to analyze what’s risky and what isn’t: Nearly everyone he speaks to is in constant contact with forest creatures. “It’s not like, ‘Oh, it was the people who ate the salmon mousse at church breakfast,'” he told me. To complicate matters, wild and domestic animals can act as intermediaries between humans and a real reservoir, says Stephanie Seifert, a disease ecologist at Washington State University. Researchers sometimes have to traverse networks of interaction, moving through Kevin Bacon-esque degrees of separation to locate the original source.
Revealing those natural origins is key to preventing the virus from moving to new properties — and perhaps breaking existing leases. In Central and West Africa, for example, where some people depend on hunting and eating game for their livelihood, “You can’t just say, ‘Don’t hang out with rodents,'” Seifert told me. But with more research, says Clement Meseko, a veterinarian and virologist who studies the human-animal interface at the National Veterinary Research Institute in Nigeria, experts may eventually be able to identify just a few species and recommend sustainable alternatives instead. Improved sanitation to keep rodents away from people can also help. The same goes for distributing vaccines to people living in high-risk areas of endemic countries — or perhaps to alarm wildlife themselves. (Immunizing animals is a pretty lofty goal, but could still be a better alternative to killing animals, which “often doesn’t work,” Lloyd-Smith said.)
In the US, amid the current outbreak of monkey pox cases, the CDC has recommended that infected people avoid interacting with pets, livestock and other animals altogether. While a cat or dog has never been known to contract the infection, “we don’t actually know anything about monkeypox in common companion animals,” Doty said. For now, it’s best to play it safe.
And the most meaningful way to prevent the virus from entering a new animal species, Han said, “is to contain the human outbreak.” The species range of monkeypox is already formidable, and in today’s world people and animals collide more often. Amid the ongoing outbreak, Meseko, who spends the year completing a fellowship in St. Paul, Minnesota, has taken note of “how squirrels everywhere are just free.” Whatever threat they pose to us, “animals are also at risk from humans,” he told me.
After all, human activity brought monkey pox to the US in 2003 and in a cabal of prairie dogs including Chewy and Monkey. “They wouldn’t have been exposed geographically without moving us around this virus,” Seifert said. And the human desire for pets brought those prairie dogs into dozens of homes across the Midwest. People mobilize disease; our species also poses an immense contagious threat to the planet. For example, the current monkeypox outbreak is more expansive and people-oriented than those documented in the past. And the more likely the virus has to infiltrate new hosts, the more likely it has to expand its species range. Every droplet in animals may be discovered too late; perhaps some experts pointed out that it happened a long time ago and seeded a reservoir that contributed to the outbreak of the ongoing epidemic. “We have no evidence of that at this time,” said Grant McFadden, a smallpox virus expert at Arizona State University. “But that could change on a dime.”