title: Update: influenza activity--United States, worldwide.
mesh_terms: D000349:Africa; D001130:Arizona; D005060:Europe; D006801:Humans; D009980:Influenza A virus / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000382:microbiology; D007723:Korea; D008297:Male; D008875:Middle Aged; D014481:United States