That’s one of the leading hypotheses about the high-mortality influenzas — that they cause cytokine storms that in turn cause shock and death. I talked about that here most recently. Earlier I was skeptical, and I’m still not 100% that’s a common problem, but I’m coming around.

But the cytokine storm idea is mainly for the highly lethal strains of flu, like the 1918 strain and H5N1 avian flu. For standard flu strains, the immune response probably does cause some of the symptoms (that’s true for virtually every infection, of course) but isn’t as serious as the virus per se.

(It’s always hard to tease apart the relative contributions of pathogen and immune response, but a general truth is that the immune system may cause nasty symptoms, but without an immune response the infectee dies pretty fast.)

I thought I’d read somewhere that the body’s response to the influenze virus can actually cause as much harm as the virus itself. Is that hokum, or is there any truth to it?