Cats are susceptible to natural infection with several strains of feline coronavirus that may result in either effusive and noneffusive FIP disease or in subclinical to severe enteritis. Investigators are still unsure of the routes by which strains of coronavirus are transmitted between cats. Excretion of coronavirus by infected cats into the environment occurs by way of feces, oronasal secretions, and, possibly, urine. FIP coronavirus remains stable outside the host for as long as 3 to 7 weeks and is rapidly inactivated by most household disinfectants. Clinical diagnosis of coronavirus infection is made by evaluating the presenting history, physical findings, laboratory results, coronavirus antibody titers, and by excluding analogous disease. The presence of coronavirus antibodies can be used to screen cats for the presence of coronavirus infection and as an adjunct in diagnosing clinical coronavirus infection. A intranasal TS-FIPV vaccine that protects against natural coronavirus challenge is available for healthy cats 16 weeks of age or older.