Outbreaks of influenza B: 1991.
D003430:Cross-Sectional Studies; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D004739:England / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D009981:Influenza B virus; D007251:Influenza, Human / Q000453:epidemiology*; D014852:Wales / Q000453:epidemiology