I’ve been reading more medical articles than I should on this - but I do have some time on my hands...
The ‘normal’ flu has about a 0.1 % mortality rate - Covid has been harder to judge (lots of people not tested or such minor symptoms they didn’t know they had it) , but at best 1% and at worst 3-4% mortality - Per year this means about 3-4 hundred thousand deaths for a normal flu, and about 30+ million for Covid .
That and the fact it will come in various waves means the health system wouldn’t handle it, and doctors are left deciding who to let live and die due to shortages of ventilators.
I’d say flight training for GA/airline pilots would struggle to prove itself as ‘essential’ at the moment and it is a very good environment for virus transmission .