Influenza.
D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D005858:Germany / Q000453:epidemiology; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007223:Infant; D009980:Influenza A virus; D009981:Influenza B virus; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D007558:Italy / Q000453:epidemiology; D007623:Kazakhstan / Q000453:epidemiology; D009017:Morbidity; D014481:United States / Q000453:epidemiology