Investigating the effect of high spring incidence of pandemic influenza A(H1N1) on early autumn incidence
Investigating the effect of high spring incidence of pandemic influenza A(H1N1) on early autumn incidence
A pandemic H1N1 infection wave in the USA occurred during spring 2009. Some hypothesized that for regions affected by the spring wave, an autumn outbreak would be less likely or delayed compared to unaffected regions because of herd immunity. We investigated this hypothesis using the Outpatient Influenza-like Illness (ILI) Network, …