> Now, I suppose in principle you could have a virus that causes respiratory symptoms, but that affects some other organ more than the lungs, but I'm not sure h

> Now, I suppose in principle you could have a virus that causes respiratory symptoms, but that affects some other organ more than the lungs, but I'm not sure how plausible that is biologically Chicken pox? It's spread through the respiratory system, but primarily affects the skin and nervous system. And it's enormously contagious: we wouldn't have a chance to contain it in a population that started with zero immunity.