Includes subtyping one positive sample per case. Appropriate swabs to use for influenza virus PCR are synthetic (Dacron or Rayon) tipped swabs on plastic shafts. Swabs should be placed in 1 ml of PBS in a falcon snap cap tube and the shaft broken low enough to allow the cap to be securely snapped tightly and avoid leakage. Do not send swabs in agar or gel-type media. Avoid using any calcium-alginate-tipped swabs or bleach. Also avoid cotton swabs with wooden shafts. Ship swabs overnight to the diagnostic laboratory. Acceptable swabs: Star Swab II, Copan swabs, Other swabs are also available.