Bat-derived coronavirus infects nearly 70,000 a year, study says

Every year, nearly 70,000 people are being infected with some type of coronavirus from bats in Southeast Asia, estimates an international team of researchers. The number helps to give a more concrete dimension to the size of the public health problem posed by the increase in interactions between humans and flying mammals – it is very likely that Covid-19 came about this way.

Luckily for humanity, almost all of these cases are a kind of dead end in epidemiological terms. That is, in general, only the person who has had direct contact with bats or their body fluids ends up getting sick and, after a few weeks, manages to recover without the virus being transmitted to other people. However, the accumulation of cases, over time, increases the chances that one of these disease causes will acquire a greater capacity to infect humans.

The methods that made it possible to estimate the size of this risk are described in an article that has just appeared in the scientific journal Nature Communications. One of the coordinators of the survey is Peter Daszak, from the EcoHealth Alliance in New York, who is also part of the team whose work has pinpointed the probable origin of Covid-19 in a wild animal market in Wuhan, China.

“We think the people who are most at risk are those who come into contact with feces, saliva, urine or bat blood,” Daszak explained to Sheet. “They could be doing this unknowingly, touching the animals’ urine or feces in a cave or where they forage at night.”

“The risk is also high for those involved in hunting and processing bat corpses and for those working in the trade and breeding of other wild mammals that also carry bat-derived coronaviruses,” he says. “We’re talking about tens of millions of people in that region.”

Among these species are several small carnivores typical of the region, such as civets, raccoon dogs and badger ferrets. It is estimated that the breeding market for these and other wild species moves tens of billions of dollars in the region annually.

To arrive at the estimate of annual infections, Daszak and his colleagues first took into account the geographic distribution of the habitats of 26 species of bats that are known to carry respiratory-transmitted coronaviruses in their body, similar to the one that causes the current pandemic, and also of two diseases that emerged since the beginning of this century, Sars and Mers.

There are at least two major environmental factors that are important for the presence of these animals: forests and limestone shelters (with caves where they can live), although some species have also colonized agricultural regions and urban areas.

Thinking only of the number of bat species that carry coronavirus, the regions most at risk are southern China, eastern Myanmar and northern Laos. Adding together species richness and human population density as requirements, the problem is once again more acute in southern China and Myanmar, and is also a concern in northern India and the island of Java, in Indonesia.

Combining this data on the most exposed populations with information on the presence of antibodies (a sign of infection by different coronaviruses) and the frequency of contact between humans and bats, the team arrived at an estimate of 66,000 infections per year. Depending on the statistical parameters used, the number could be lower, around 39,000 cases.

There are no simple ways to reduce the risk, according to the expert. “Unfortunately, human behavior is complex, so our strategy also needs to be complex,” he says.

“A good start is to work with people in high-risk occupations — those who collect bat droppings in caves to use as fertilizer or in traditional medicine, those who work on farms and markets with wild animals. protection, washing your hands and avoiding contact with the animals can help a lot. We are also working with villagers who live near the caves to teach them the value of these animals, how to avoid contact and reduce the risks to their health, which will reduce the risk for everyone on the planet.”