Detection of influenza a subtypes in community-based surveillance

A rapid microtitre cell enzyme immuno assay (cell-EIA) was developed for the detection of influenza A subtypes in nasopharyngeal(NPS) swabs taken for surveillance. During the 1997/1998 influenza season in the United Kingdom, cell-EIA was compared to cell culture for the detection and typing of influenza A viruses in NPS obtained by sentinel general practitioners in community surveillance. The cell EIA can also be used to detect different influenza A subtypes (H3N2, H1N1, H5N3, H5N1, H7N7, and H9N2) and was used as a rapid detection assay for the screening of individuals returning from Hong Kong with influenza-like illness suspected to be due to H5N1 in 1997/98, providing a rapid, efficient, inexpensive method for the screening of influenza A cases during an outbreak or pandemic situation. The cell-EIA results reflected the results obtained by traditional virus culture within the age distribution of samples, clinical symptoms, and time between date of illness onset and sampling of cases, indicating its usefulness in surveillance of human and non-human influenza viruses. During two outbreaks of influenza in schools, Directigen Flu-A, a near patient test, the cell-EIA, and tissue culture were compared. The cell-EIA gave higher sensitivity and specificity (74% and 90%) than Directigen Flu-A (65% and 84.6%) in comparison with cell culture.