Influenza.
D000328:Adult; D000368:Aged; D002648:Child; D003430:Cross-Sectional Studies; D004196:Disease Outbreaks; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D009980:Influenza A virus; D007251:Influenza, Human / Q000453:epidemiology* / Q000382:microbiology; D008297:Male; D014852:Wales / Q000453:epidemiology