Between November 1995 and January 1996, 41 patients were admitted to the Infectious Disease Unit at the Royal Hallamshire Hospital, Sheffield, with symptoms and signs consistent with influenza. Thirty nine of these patients gave their informed consent to undergo nasopharyngeal aspiration in addition to routine investigations. The procedure was performed with a small suction catheter and trap. Viral transport medium was added to the aspirate and samples were sent to the laboratory within 24 hours. Nasopharyngeal aspirates and throat swabs were cultured by standard methods in primary monkey kidney cells at 33°C and 37°C.1 In addition, rapid culture was performed on nasopharyngeal aspirates, throat swabs, and viral transport medium; samples were centrifuged on coverslips in shell vials and then incubated at 37°C before fixation with methanol after 24 hours and 48 hours. The specimens were then stained with fluorescein isothiocyanate.2 For direct immunofluorescence, cells from nasopharyngeal aspirates were air dried, fixed on slides coated with Teflon, and stained with the labelled influenza A and B monoclonal antibodies.