The ability to accurately predict influenza infection by symptoms and local epidemiology prior to lab confirmation warrants further study and is particular concern as the threat of pandemic flu heightens. Antiviral drugs are effective when given within 48 hours of symptom onset, but this usually precludes culture confirmation. Further, rapid tests can be clinically helpful but lack the sensitivity of viral culture. Hence, ILI symptoms are a potentially important covariate in the early diagnosis of flu. However, gaps remain in several areas of flu symptom research, including knowledge of potential differences between symptoms of Influenza A and of Influenza B [1]. Therefore, an examination of symptoms generally associated with Influenza infection was begun, as well as an examination of symptoms specifically associated with Flu A and Flu B. An additional focus in this study was to evaluate the performance of the current ILI case definition used by the DoD flu program. This definition is useful to identify individuals who are likely to be infected with influenza, as the ability to capture and characterize novel strains of influenza is an important component to this program. Better yields of influenza mean less time and money spent processing negative specimens.
Objective
This study describes clinical symptoms reported in conjunction with influenza, non-influenza respiratory viruses, and negative viral cultures from the Department of Defense (DoD) Global Influenza Surveillance Program; influenza-like illness (ILI) case questionnaires were linked to corresponding laboratory specimen results for the 2005-06 influenza season for analysis.