RNA was extracted from nasal wash as previously described [32 (link)]. A total of 4 µL RNA was assayed by real-time RT-PCR with influenza virus–specific primers and probes, using the SensiFAST Probe Lo-ROX One-Step Kit, according to the manufacturer's instructions (Bioline), on the 7500 Fast Real-Time system (Applied Biosystems). Primers and probes were from the Centers for Disease Control and Prevention (CDC) Influenza Virus Real-Time RT-PCR Influenza A (H1/H3/H1pdm09) Subtyping Panel and the CDC Influenza B Lineage Genotyping Panel, obtained from the Influenza Reagent Resource (available at: http://www.influenzareagentresource.org/).