Coronaviruses are fairly common among mammals, especially so in bats. When the now-named COVID-19 began becoming a household name, it was linked to the consumption of bats at a market in Wuhan, China, the epicenter of the pandemic. Although the origin of COVID-19 has not been confirmed in the five months since the outbreak, bats are a strong possibility. While most researchers are working on ways to fight the virus, a biologist from Chicago’s Field Museum is going back to the beginning by examining the genetic relationships between different strains of coronaviruses present in bats.
“Before you can actually figure out programs for public health and try to deal with the possible shift of certain diseases to humans, or from humans to animals, you have to know what's out there. This is kind of the blueprint," said Steve Goodman, field biologist and author of a recent paper released in Scientific Reports that has revealed an interesting twist in the pandemic story—bats and coronaviruses have been evolving together for millions of years.
In the study, the researchers tested 1,013 bats belonging to 36 species from the western Indian Ocean and nearby areas of Africa. Eight percent of the bats sampled were carrying a coronavirus. A genetic analysis of these coronaviruses revealed that different genera of families of bats have their own unique strains of the virus.
For example, fruit bats of the family Pteropodidae from different continents and islands formed a cluster in their tree and were genetically different than the coronavirus strains of other groups of bats found in the same geographical zones.
“Based on the evolutionary history of the different bat groups, it is clear that there is a deep coexistence between bats—at the level of genus and family—and their associated coronaviruses,” said Goodman.
In rare cases, bats of different families, genera and species that lived in the same caves and had close day roost sites shared the same strain of coronavirus but, overall, transmission between species was found to be very unlikely.
Goodman and colleagues took the research a step further and built a giant coronavirus family tree that compares the coronaviruses sequenced from bats in this study with ones from other mammals, including dolphins, alpacas and humans. The tree shows how different types of coronaviruses are related to each other. The researchers believe understanding the evolution of these strains could be key for preventing future coronavirus outbreaks.
“The development of serological methods targeting coronavirus strains circulating in the Indian Ocean will help show whether there have already been discrete passages in human populations, and their interaction with the hosts will allow a better understanding of the emergence risk,” said study co-author Patrick Mavingui, microbial ecologist and head of the PIMIT Laboratory.
Interestingly, the research team believes the 8 percent of bats studied with coronaviruses is smaller than the actual number, as there is increasing evidence for seasonal variation in the spread of the virus among bats. Thus, the number of infected bats may significantly vary depending on the time of year. During the pandemic, some researchers have proposed COVID-19’s transmission rate will naturally decrease as summer hit the states. While this idea if not conclusive, COVID-19 most likely has seasonal roots, and it wouldn’t be the first virus to have a prime “season.” There’s a reason annual flu shots are offered in October, after all.
Photo: Fruit bats (Rousettus madagascariensis) from Northern Madagascar derive from a species that carries a form of coronavirus. Credit: Olivà S. Noroalintseheno Lalarivoniaina.