Monkeypox virus, illustration.
Thom Leach | Science photo library | Getty Images
In 2003, 47 people in six Midwestern states caught monkeypox from prairie dogs as pets that were infected after being housed with rodents imported from Ghana, Africa.
Today’s outbreak, which has already infected more than 14,100 people in the US and more than 41,000 worldwide, spreads primarily through close human contact between gay and bisexual men. But scientists this month reported the first suspected human-to-pet transmission in a dog in France, prompting US and global health officials to step up warnings to ensure the virus doesn’t spread to other pets and animals.
The recommendation stems from concerns that monkeypox could enter the wild or rodent populations as the human outbreak expands, allowing the virus to move back and forth between humans and animals and establishing a foothold in countries where it has not circulated historically. .
Prior to this year’s global outbreak, monkeypox spread mainly in remote parts of West and Central Africa, where people contracted the virus after exposure to infected animals. The 2003 outbreak, which was contained, was the first documented case of people contracting the virus outside of Africa.
The current global outbreak differs dramatically from previous transmission patterns. Monkeypox now spreads almost entirely through close physical contact between people in major metropolitan areas in the US, European countries and Brazil.
But the first suspected case of humans infecting an animal in the current outbreak was reported in France this month. A dog tested positive for the virus after a couple in Paris fell ill with monkey pox and shared their bed with the animal.
WHO officials have said a single incident of a pet contracting the virus is not surprising or cause for great concern, but there is a risk of monkeypox circulating in animals if people don’t know they can infect other species.
If monkeypox establishes itself in animal populations outside of Africa, the virus would have more potential to mutate, carrying the risk of higher transmissibility and severity. Animals could then potentially transmit the virus to humans, increasing the risk of future outbreaks.
“What we don’t want to see happen is diseases go from one species to another and then stay with that species,” said Dr. Mike Ryan, director of the WHO’s health emergencies program, at a press conference in Geneva last week. . “It’s through that process of one animal affecting the next and the next and the next that you see rapid evolution of the virus.”
The Centers for Disease Control and Prevention have received no reports of pets infected with monkeypox in the US, said Kristen Nordlund, an agency spokesperson. But the virus can spread from human to animal or from animal to human, according to the CDC.
“While we’re still learning which animal species can get monkeypox, we have to assume that any mammal can be infected with the monkeypox virus,” Nordlund said. “We don’t know if reptiles, amphibians or birds can get monkeypox, but it’s unlikely because it has been established that these animals are not infected with viruses in the same family as monkeypox.”
dr. Rosamund Lewis, the WHO’s leading expert on monkey pox, said it is important to dispose of potentially contaminated waste properly to avoid the risk of rodents and other animals becoming infected when they rummage through waste.
“While these have always been hypothetical risks, we believe they are important enough that people should have information about how to protect their pets and manage their waste so that animals in general are not exposed to the monkeypox virus. ‘ said Lewis.
Ryan said that while vigilance is important, animals and pets pose no risk to humans at this time.
“It’s important that we don’t allow these viruses to establish themselves in other animal populations,” Ryan said. “Single exposures or one-time infections in certain animals are not unexpected.”
Rodents in Africa
Although scientists have done some research on monkeypox in Africa, where it has historically circulated, their work has been limited due to a lack of funding. So scientists don’t know how many different animal species can carry the virus and transmit it to humans.
Scientists have isolated monkeypox from wild animals in Africa only a handful of times in the past 40 years. These included rope weekhorns, target rats and giant possums in the Democratic Republic of Congo, as well as two species of monkeys in Côte d’Ivoire. Rodents, not monkeys, are considered the host animal population in Africa, although the precise animal reservoir is unknown.
Public health officials don’t know whether the species of animals in close proximity to humans in urban environments across the US — raccoons, mice and rats — can pick up and transmit the virus. Some species of mice and rats can get monkey pox, but not all species are susceptible, according to the CDC.
“We know this is a virus transmitted by rodents in West Africa,” said Dr. Peter Hotez, an infectious disease expert at Baylor College of Medicine in Texas. “Could rats or other rodents in urban environments mean it’s gaining a foothold there and also becoming more of a fixture — we don’t want that to happen,” he said.
The CDC recommends that people who have monkey pox avoid contact with animals — pets, livestock, pets and wildlife. If a pet becomes ill within 21 days of contact with someone who has monkey pox, the animal should be evaluated by a veterinarian.
Waste contaminated with monkeypox should be placed in a lined, special trash can and should not be left outside because wildlife could potentially be exposed to the virus, the CDC said.
US outbreak in 2003
In the 2003 outbreak, the CDC was able to quickly administer vaccines and quarantine patients before the virus could spread further. There were no cases of monkey pox spreading between humans. The CDC then banned the importation of rodents from Africa.
According to Marguerite Pappaioanou, a former CDC official who worked on the outbreak, it took 10,000 hours of work to contain the 2003 outbreak, according to Marguerite Pappaioanou, a former CDC official who worked on the outbreak.
The Food and Drug Administration banned the importation of all African rodents in the wake of the 2003 outbreak. The agency also banned the dispersal of prairie dogs between states and their release into the wild over concerns that monkeypox could establish itself in wildlife populations. .
The US Georgian Survey and the Department of Agriculture subsequently captured 200 wild animals in Wisconsin at sites near where humans contracted monkeypox from prairie dogs. They found no evidence that the virus had spread to wild animals, and the FDA lifted the ban on spreading prairie dogs between states. It is still illegal to import rodents from Africa.
Scientists in California discovered monkeypox DNA in sewage samples this summer. New York is also monitoring wastewater from the virus, according to the state’s health department, although the results have not yet been released publicly. The California wastewater findings have raised concerns among some health experts that the virus could infect rodents through the sewer.
“There’s a risk because of the widespread nature of infections and the fact that it’s sewage and wastewater,” says Dr. James Lawler, an infectious disease expert at the University of Nebraska Medical Center’s Global Center for Health Security. “That’s a concern, to get into an animal population and have a zoonotic risk reservoir and frankly, if that’s the case, I think it’s game over for us.”
But it is not clear whether live virus is present in wastewater. According to Marlene Wolfe, an Emory University scientist working on the project, monkey pox DNA was measured in sewer samples, not whether the virus was still contagious.
Wastewater is treated in most urban areas, so the chances of the virus surviving and multiplying in such an environment are slim, according to Amira Roess, a former official with the CDC’s Epidemiological Intelligence Service. Roess said that waste containing contaminated materials such as bedding or towels is likely to pose a higher risk than wastewater.
“There are species of animals that will sniff your waste and then they are more likely to pick up a virus that can reproduce. “There are a lot of ifs, but it happens,” says Roess, who is now a professor of epidemiology at George Mason University.
According to Richard Reithinger, an epidemiologist at RTI International, several steps would have to be taken to allow the monkeypox virus to pass from humans to animals and then flow back into humans, triggering another outbreak.
The virus should circulate in an animal population with a wide geographic distribution, but not cause so much death in the species that the transmission train is extinguished, Reithinger said. Humans should also have some level of regular contact with animals.
“Every step has a certain probability. Once you add up all the probabilities of these steps, the probability actually gets pretty low,” Reithinger said.
It’s also possible that monkeypox is more efficiently transmitted among humans during the current outbreak due to some type of viral mutation, Roess said. Once the virus has adapted to humans, it may be more difficult for humans to pass the disease on to animals, she added. It also depends on what kind of animal comes into contact with the virus, Pappaioanou said.
“Not all animals are susceptible. We don’t even know which ones they are,” said Pappaioanou, who is now an associate professor at the University of Washington.
Need better supervision
While the risk of the virus anchoring in a US animal population and causing future human outbreaks is low, the US needs a more robust surveillance system to prepare for such a possibility, according to Pappaioanou and Roess. There are major gaps in the ability of public health agencies to monitor animal populations for infectious diseases, the former CDC officials said.
“It’s a very big hole. We don’t have a good surveillance system for people,” Roess said. “For wildlife, it depends on who is interested in which pathogen and whether they can convince someone to fund surveillance. Much of our surveillance is sporadic”
Livestock such as cows, sheep and poultry are controlled by the Ministry of Agriculture, Pappaioanou said. But wildlife surveillance is underfunded and it takes a huge amount of work to monitor these animals for infectious diseases, she said. There is no government agency that monitors the health of dogs and cats abroad, she said. Local health departments can monitor rodents and have population control programs in place, but this also requires funding and significant staffing, she added.
“More and more people around the world are moving to cities,” Pappaioanou said. “What would it mean in a highly urbanized city to have a reservoir of infection? We don’t know the answer.”