Re: Government Guidance
Bah. Points for etymology, but minus several million for unjustified prescriptivism.
There are an infinite number of ways to form a plural of "virus" in English. Here's one: slaijhviels. Unlikely to catch on, I know; but that doesn't mean it's not "a way to make the noun 'virus' plural". Nothing in the conventions of English as a spoken or written language forbids it, and there is no authority for the language generally recognized by a majority of Anglophones.
And that, of course, is the usual problem with prescriptivists. They can formulate a learned argument, but then they try to build it on a foundation of appeal to some imaginary authority, because they can't bear to simply be descriptive and argue a preference.