First evidence of a pro-inflammatory response to severe infection with influenza virus H1N1.

The great majority of infections caused by the pandemic variant of the influenza virus (nvH1N1) are self-limited, but a small percentage of patients develop severe symptoms requiring hospitalization. Bermejo-Martin and colleagues have presented a pilot study describing the differences in the early immune response for patients both mildly and severely infected with nvH1N1. Patients who develop severe symptoms after nvH1N1 infection showed Th1 and Th17 'hypercytokinemia', compared to mildly infected patients and healthy controls. The mediators involved with the Th1 and Th17 profiles are known to be involved in antiviral, pro-inflammatory and autoimmune responses. This is the first work reporting the association of a pro-inflamatory immune response with a severe pandemic infection, although it is likely that more studies are needed to understand the detrimental or beneficial roles these cytokines play in the evolution of mild and severe nvH1N1 infection.