SARS-like coronaviruses may jump from animals to people hundreds of thousands of times a year

#SARS-like coronaviruses may jump from animals to people ~400,000 times per year in undetected spillovers, according to a new study (not yet peer-reviewed). The study also identifies Asian regions that could spark the next #coronavirus pandemic.

Only two new coronaviruses have spread globally the past 2 decades: SARS-CoV, which caused an outbreak of severe acute respiratory syndrome (SARS) in 2003, and SARS-CoV-2, the virus that causes #COVID19. But that may just be the tip of the iceberg of undetected infections with related viruses emerging from bats, a new paper claims. In a preprint published yesterday researchers estimate that an average of 400,000 people are likely infected with SARS-related coronaviruses every year, in spillovers that never grow into detectable outbreaks.

Although that number comes with big caveats, “It should be eye-opening to the entire scientific community that we don’t know very much about the frequency of zoonotic spillover,” says virologist Angela Rasmussen of the University of Saskatchewan, who was not involved in the work. That needs to change, she says, “because otherwise we grossly underestimate it.”

The researchers, including Peter Daszak from the EcoHealth Alliance and Linfa Wang from Duke-NUS Medical School in Singapore, created a detailed map of the habitats of 23 bat species known to harbor SARS-related coronaviruses, the group to which SARS-CoV and SARS-CoV-2 belong, and then overlaid it with data on where humans live to create a map of potential infection hot spots. They found that close to 500 million people live in areas where spillovers can occur, including northern India, Nepal, Myanmar, and most of Southeast Asia. The risk is highest in southern China, Vietnam, Cambodia, and on Java and other islands in Indonesia (see map, below).

“This is a definitive analysis of where on the planet the next SARS- or COVID-like virus is most likely to emerge,” Daszak says. The maps could guide efforts to reduce the likelihood of spillover by changing behaviors in high-risk communities and targeting surveillance to detect new outbreaks earlier, he says. Daszak, a vocal advocate of the hypothesis that SARS-CoV-2 came from the wild instead of a research lab, says the maps could also guide efforts to find the virus’ natural origin. (Several studies are underway or being planned to look for SARS-CoV-2 and its relatives in Rhinolophus [horseshoe] bats and other animals.)

But the researchers went one step further. Small surveys done before COVID-19 erupted have suggested some people in Southeast Asia harbor antibodies against SARS-related coronaviruses. Combining those data with data on how often people encounter bats and how long antibodies remain in the blood, the researchers calculated that some 400,000 undetected human infections with these viruses occur each year across the region.

Figure. A map in a new paper shows the relative spillover risk for severe acute respiratory syndrome–related coronaviruses. China and countries in Southeast Asia are potential hot spots for human infections.

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