Virological surveillance of influenza A.
D004739:England / Q000453:epidemiology; D006801:Humans; D009980:Influenza A virus / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000382:microbiology*; D011159:Population Surveillance; D014852:Wales / Q000453:epidemiology