Bats in Switzerland do not harbour dangerous viruses
Virologists at the University of Zurich have identified 39 virus families in Swiss bats, including coronaviruses. They say there is no danger to humans.
Bats are considered the most likely origin of the coronavirus SARS-CoV-2, although the exact source has not yet been conclusively established.
In faecal and tissue samples from bats living in Switzerland, virologists at the University of Zurich have searched for viruses. They discovered 16 virus families capable of infecting vertebrates, including coronaviruses. However, they do not consider these to pose a danger to humans.
Thousands of different viruses have already been identified in bats; some of them can infect humans directly or via an intermediate host. These zoonotic viruses include not only various coronaviruses, but also the rabies, Marburg, Ebola, Nipah, and Hendra viruses.
The team led by Cornel Fraefel and Jakub Kubaki from the Institute of Virology at the University of Zurich, together with the Clinic for Zoo Animals, Exotic Pets and Wildlife at the Zurich Tierspital and the Bat Protection Foundation, set out to hunt for viruses for which bats in Switzerland serve as a reservoir.
Using genomic analyses, the researchers examined faecal and tissue samples from 7,291 bats belonging to 18 native bat species, in which they were able to identify 39 different virus families. They report their findings in the journal «Plos One». The greater mouse-eared bat proved to be particularly rich in viruses, harbouring 33 virus families.
Among the collection were 16 virus families capable of infecting vertebrates, including coronaviruses, adenoviruses, hepeviruses, rotaviruses, and parvoviruses. For instance, the researchers discovered a beta-coronavirus in a colony of parti-coloured bats that resembles the MERS pathogen and has already been detected in other European countries.
The respiratory disease Middle East Respiratory Syndrome (MERS) first appeared in 2012 in Saudi Arabia, where the virus likely jumped from bats via camels to humans. The mortality rate among those infected is around 35 percent.
However, the MERS-like virus discovered in Swiss bats does not infect humans. Furthermore, no coronavirus is yet known to have jumped directly from bats to humans without passing through an intermediate host, said Fraefel in conversation. «In our view, there is absolutely no risk.»
While it cannot be ruled out that the virus might find its way into an intermediate host, mutate there, become more virulent, and ultimately jump to humans as a pathogen, contact between bats, other wild animals, and domestic animals is far lower in Switzerland than in Asia, for example, said Fraefel.
As part of a follow-up study, the virologists aim to investigate how mutations accumulate in the genome of the MERS-like virus under natural conditions within the colony of parti-colored bats.
They will also continue to examine fecal and tissue samples in order to obtain an even more comprehensive picture of Switzerland's bat virome. The researchers had in fact expected to encounter herpes or rabies viruses as well. The latter are assumed, based on an earlier study, to occur in native bats.
