The influenza virus is divided into three types-A, B and C-with the influenza A virus affecting mammals and birds, influenza B virus infecting only humans and seals, and influenza C virus causing very mild symptoms.
流感病毒分成 A、B、C3 型，A 型感染哺乳動物和禽鳥，B 型只感染人類和海豹，C 型則症狀輕微。