[set fair (OP)]

In NS podcast 'Where Did COVID Come From?'  we heard that bats shed the virus periodically and later that they shed more when under stress. So could there be a purpose to the shedding - defensive or aggressive?

[alancalverd]

A virus that kills 6%  of some infected species about 30 days after infection, is not a great defence against predators.

Komodo dragons infect their prey and then stalk it for hours or days, but bats eat either flying insects (which have to be caught at full intercept speed) or fruit (which literally hangs around waiting to be eaten).  Vampire bats occasionally infect cattle but a live cow is not a threat and a dead cow is not a source of fresh blood.

As coronaviruses are distributed through exhalate, it is hardly surprising that a stressed bat sheds more.

[chris]

No, bats do not use coronaviruses for defence. Bats support coronavirus circulating in exactly the same way that humans support the circulation of coronaviruses: there are 4 common human coronaviruses that cause a significant proportion of the colds we develop each winter. Those viruses are well adapted to us, and bat strains are well adapted to them. Any species, when stressed, will increase its susceptibility to infection and also take longer to clear infections for reasons of immune compromise secondary to stress.

[evan_au]

Bats don't use coronavirus as a weapon.

Coronaviruses use bats (and humans) as victims.