Two months in the international monkeypox epidemic, which has so far caused nearly 6,000 infections in the United States and more than 18,000 cases worldwide, may be old news to say that this disease has visited the US before. In 2003, the virus arrived via exotic pets imported from Ghana, sickening 72 people, including children as young as 3 years old. It sent 19 people to hospital before the outbreak burned out on its own.
Looking back, the obvious lesson seems to be how much Monkeypox has changed his behavior since then. In 2003, each case could be traced back to a person’s exposure to an infected animal. By 2022, transmission seems overwhelming from person to person, traceable to sexual or skin-to-skin contact in men who have sex with other men. But there’s an important detail in the 2003 outbreak that worries researchers as they investigate this new one. Two decades ago, the virus spread as it passed from captive African wildlife to American animals sold as pets. Those pets, wild prairie dogs, have transmitted the virus to humans.
No one had accounted for such a cross-species vulnerability because human monkeypox infections had not been previously discovered outside of West and Central Africa. At the time, it was well known that African animal species transmitted the disease to people who hunted them or lived in their territory. What was surprising was that the virus could be transmitted to wildlife from other continents. It remains a cautionary tale — and it may be a warning that the virus could establish itself in new animal populations, now that it has spread to nearly 80 countries.
This is by no means certain. But it’s already worrying that virologists are talking about the possibility of new host species in new territory — spreading that could be a “backflow” from humans to animals, creating new exposure risks beyond what’s currently known. Scientists are researching this carefully; no one wants to be seditious. “I don’t think there have been cases at this time that were clearly the result of zoonotic spillover,” said Angela Rasmussen, a virologist and associate professor at the Vaccine and Infectious Disease Research Organization-International Vaccine Center at the University of Saskatchewan. “And I think that would be obvious, because we would see cases popping up with no connection to an MSM sexual network, and that hasn’t happened yet.”
Since several rodent species have been found to harbor monkeypox in the countries where it was first identified, it’s a fair bet that multiple species may be vulnerable to it elsewhere. But there isn’t enough accumulated science to tease out the implications. Could European or American wildlife be able to pick up the disease momentarily and then get over it? Or would it become a persistent infection among them? If it became endemic to populations of wild animals, whether that be prairie dogs in the countryside or rats in cities, could it be transferred to other species that mix with it? And how close would those animals have to get to humans to pose an infectious risk — or to be endangered by human contact?
“What I take from the 2003 experience is that there is a wide range of species that are likely to be susceptible to monkeypox,” said Jason Kindrachuk, a microbiologist and assistant professor at the University of Manitoba who studies monkeypox and other zoonotic pathogens. “But we don’t quite understand what that looks like yet.”
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