Equivalence of influenza A virus RNA recovery from nasal swabs when lysing the swab and storage medium versus storage medium alone

Surveillance of healthy individuals at high risk for zoonotic influenza A transmission is important for tracking trends in influenza A epidemiology. Practical measurement methods that maximize viral recovery and produce low variability are essential when low viral loads are expected. For this study, lysing both a nasal swab and its storage medium was compared to lysing the storage medium alone to determine which method results in greater influenza A virus recovery. Independent results from two laboratories suggest that including the swab in the lysis step does not lead to higher influenza A virus recovery, and that recovery is less variable when only the swab storage medium is extracted. These results indicate that simply lysing the swab storage medium is an effective extraction method for nasal swabs collected during studies of influenza A virus exposure among healthy populations