Thats like saying the person died form lack of blood after being shot. Its technically correct, but actually useless.

Medically it seems much more specific though. You could die from numerous things after a gunshot wound, so naming the specific cause of death is more accurate.

Doesn't say which virus.

If they don't know, fine. Albeit sloppy, given the context.

If they do know, and don't say, it's deceptive.

I'm not sure that it's deceptive; generally the "cause of death" is just one part of a larger report that can give further detail.