Each year mortality increases in winter, especially in the elderly. Much of the excess is believed to be related to respiratory viral infections but robust data are scarce. Three recent papers cover this topic and provide further insights into the role of influenza.

Thompson et al provide data on national estimates of influenza associated hospital admissions in the US. This is important because previously only data on influenza associated mortality were available, which may incompletely reflect the severity of influenza infections. The authors used data from National Hospital Discharge Survey and WHO collaborating laboratories influenza surveillance to estimate the annual numbers of hospital admissions associated with influenza from 1979–80 to 2000–01. 8.6% of …