[klingoff]

Sure, but depression and immune system seem to be linked, so how do we know we aren't just more clearly separating viral components in boughts of heightened depression?

Personally I think our relationship with flu tells us a lot about the difference between our claimed ideals and our actual behavior as a society. We didn't want to know anything about it for curiosities sake and we invented all sorts of higher priorities to not study the mundane diseases between pandemics.