Symptom Patterns in 2009 Pandemic Influenza vs. Seasonal Influenza

Although 2009 pandemic H1N1 influenza has been well characterized, symptom patterns have not been compared between this illness and seasonal influenza. Now, investigators have conducted such a comparison among individuals who were treated or tested for influenza in Singapore between May and July 2009. The researchers also examined viral strain displacement and replacement.

A total of 2683 individuals were evaluated. Although most of them had symptoms, a few asymptomatic individuals (contacts of people with confirmed or suspected influenza; travelers returning from 2009 H1N1 influenza–affected areas) were also included.

Multivariate analysis demonstrated significant differences among seasonal, pandemic, and influenza-negative groups in age (P<…