There are several conditions that may cause cats to sneeze. However, sneezing that lasts more than two days is probably due to a viral upper respiratory infection (URI), similar to a "cold" that we may have. The "upper" part of the name means that the infection is limited to the nose, throat, trachea, and eyes. Lower respiratory infections involve the lungs; these are relatively uncommon in cats.
What causes upper respiratory infection?
There are seven different viruses or bacteria known to cause feline URI’s. Three of these cause serious illness, resulting in anorexia, high fever, and ulcers of the tongue and cornea (surface of the eye). These viruses are the feline rhinotracheitis virus (also called feline herpesvirus), the feline calicivirus, and Bordetella (which causes “kennel cough” in dogs). The remaining viruses cause mild sneezing for a few days but are rarely a serious problem.
Can complications occur?
As a rule, the uncomplicated forms of these viral infections are no more severe than the common cold. However, even mild infections can become life-threatening if secondary bacterial infections develop in the nose, oral cavity, or eyes. Cats so affected may also lose their appetites; this represents the single most serious complication. Once this occurs, the cat will become malnourished and dehydrated. If not corrected soon, many cats will die.
What is the treatment?
The first decision in treatment is deciding where it is best to treat your cat. Should your cat be hospitalized or treated at home? If the cat is eating, it is preferable to treat it at home. However, if there are other cats at home that are not infected, it may be best to treat it in the hospital to protect the healthy cats. These viruses are very contagious and are spread by sneezing. If your cat is not eating, hospitalization is preferred so that proper antibiotics and nutrition may be administered. If this is done quickly, all but a very few cats will recover completely. If your cat is being treated at home and stops eating, it should be hospitalized for more intense treatment.
Is prevention available?
If a cat has not become infected with the rhinotracheitis virus, the calicivirus, or Bordetella, vaccination is usually successful in preventing infection. For cats who are already carriers of these viruses or bacteria, it is still important to vaccinate. Because immunity from vaccination lasts only about 6-18 months, annual vaccinations are necessary. If a carrier cat should reactivate the virus and begin shedding, periodic vaccination provides the immune system with a "reminder." This allows the immune system to produce antibodies, the defense agents of the immune system, which can be readily available to begin fighting the infection. Thus, the cat may still develop a URI, but the consequences will be less severe and the recovery will be faster. Even indoor-only cats should be vaccinated since the viruses are air-borne; also, these cats may already be carriers of the viruses and need the periodic boost in immunity.
Can future infections occur in spite of vaccinations?
Many cats that have infections due to the rhinotracheitis virus or the calicivirus will become carriers. These cats are typically well, but they will have a recurrence of sneezing. Cats with the calicivirus constantly shed virus, and those with the rhinotracheitis only shed when stressed.