It is widely believed that SARS-CoV-2, the virus that causes Covid, spread from wild animals to humans.
But a new study claims that humans may transmit viruses to animals more often than previously thought.
Researchers reviewed published evidence of human-to-wildlife transmission events, with a focus on how these events could threaten animal and human health.
They found a total of 97 examples of human-to-wildlife transmissions involving a wide range of pathogens, from M. tuberculosis, measles, influenza and hepatitis B.
These pathogens likely spread from humans to wildlife in multiple ways, such as wildlife contact with human sewage.
Affected animals range from Asian elephant, European hedgehog, rhesus monkey, gibbon, giant panda, harbor seal and many more.
Evidence already suggests SARS-CoV-2 originated in horseshoe bats, though it’s likely the virus jumped to humans from pangolins, a scaly mammal often mistaken for a reptile.
Similarly, the deadly Ebola virus outbreak in West Africa between 2013 and 2016 is thought to have originated from bats.
The graphic summary of the new study shows the spread of the disease. A spillover describes the jump of a virus from another species, while a spillover is the virus that jumps back from humans to wild animals
Pictured is the European hedgehog (Erinaceus europaeus), which has been infected by humans with the bacterium Streptococcus pyogenes
– Mr. tuberculosis
– Influenza A
– Rotavirus A
– Hepatitis B
– Staphylococcus aureus
An international research team led by scientists from Georgetown University is the author of the new study, published today in Ecology Letters.
“There has understandably been tremendous interest in human-to-wild animal transmission of pathogens in light of the pandemic,” said study author Gregory Albery, from the Department of Biology at the Institute. Georgetown University.
“To help guide the conversations and policies surrounding the return of our pathogens in the future, we dug into the literature to see how the process has played out in the past.”
The researchers emphasize that they looked at human-to-wildlife transmission events – not wildlife-to-human transmission events like Covid and Ebola (although there is evidence that Covid has “thrown” humans on certain animals such as deer since we first contracted in 2019).
The team found that nearly half of identified incidents occurred in captive environments like zoos, where veterinarians closely monitor animal health and are more likely to notice when a virus makes the leap.
Additionally, more than half of the cases they found were specifically human-to-primate transmission.
Pathogens likely spread from humans to wildlife in multiple ways, such as contact with human waste (a). Other modes of transmission involve animal bites (b), meat consumption (c) and vector transmission (d). Blue arrows indicate wildlife-to-human transmission and green arrows indicate human-to-wildlife transmission
This was not surprising given that pathogens have an easier time jumping between hosts and wild populations of endangered great apes are so closely monitored.
“This supports the idea that we are more likely to detect pathogens in places where we spend a lot of time and effort searching, with a disproportionate number of studies involving charismatic animals in or near zoos. humans,” said author Anna. Fagre at Colorado State University.
“It calls into question the interspecies transmission events we are missing, and what that might mean not just for public health, but also for the health and conservation of infected species.”
Several animals, including the wild pig, the maned wolf and the crabeater fox, have been infected with the hepatitis B virus.
Although it is not known how, it may be due to fluid transfer caused by violent altercations between the human and the wild animal.
The study refers to “spillovers” (the jump of a virus from another species) and “spillback” (a virus jumping from humans to wild animals).
The spread of the disease has recently attracted considerable attention due to the spread of SARS-CoV-2 in wild whitetail deer in the United States.
The deer in question was thought to have caught Covid from humans by drinking contaminated water, as research has already shown that the virus persists in human faeces and sewage.
About 35% of 360 white-tailed deer (Odocoileus virginianus, pictured) tested positive for Covid in Ohio, researchers reported in December 2021 (stock image)
Some data suggests that deer have passed the virus back to humans in at least one case, and many scientists have expressed broader concerns that new animal reservoirs could give the virus additional chances to develop new variants.
Albery and his colleagues say artificial intelligence (AI) can be used to anticipate which species might be at risk of contracting SARS-CoV-2.
When the researchers compared the species infected with SARS-CoV-2 to predictions made by other researchers earlier in the pandemic, they found that the scientists were able to guess correctly more often than not.
“It’s quite satisfying to see that sequencing animal genomes and understanding their immune systems has paid off,” said study author Colin Carlson of Georgetown University Medical Center.
“The pandemic has given scientists the opportunity to test some predictive tools, and it turns out that we are better prepared than we thought.”
The fallout may be predictable, the authors conclude, but the bigger problem is how little we know about diseases in wildlife.
“We watch SARS-CoV-2 more closely than any other virus on Earth, so when a comeback happens, we can catch it,” Carlson said.
“It’s even more difficult to credibly assess the risks in other cases where we are not able to operate with as much information.”
NEW STUDIES SHOW COVID PANDEMIC ‘HOME FROM WUHAN SEAFOOD MARKET’
Two studies of the coronavirus outbreak published in February 2022 claim that the pandemic did indeed result from live animals being sold at a Chinese wet market in Wuhan.
The studies challenge an alternative theory that the virus leaked from nearby Wuhan Institute of Virology labs.
The co-author of both studies is Michael Worobey, an evolutionary biologist at the University of Arizona, who says the evidence is clear.
“When you look at all the evidence together, it’s an extraordinarily clear picture that the pandemic started in the Huanan market,” Worobey told the New York Times.
Worobey had previously signed a letter demanding more research into what is called “lab leak theory” and is known by his colleagues to have a “soft spot for wild theories”.
However, some prominent scientists believe in the “lab leak theory”, including Harvard scientist Dr. Alina Chan.
In December 2021, Dr Chan told British MPs that the Wuhan lab leak was the most likely origin of the coronavirus pandemic and that officials in Beijing had tried to cover it up.
We may never be able to conclusively establish the true origin of Covid.