What causes feline upper respiratory infections?
Approximately 90% of all upper respiratory infections in cats are caused by two common viruses: feline herpesvirus-1 and feline calicivirus. Feline herpesvirus is related to the virus that causes cold sores and chicken pox in people; however, people cannot get sick from the feline virus. Upper respiratory infections in cats can also be caused by fungi or bacteria. It is common for cats to be “co-infected” — infected with more than one agent (e.g., a virus and a bacteria) at the same time — which can make treatment and recovery longer and more difficult.
