Distemper in Cats (source: American Veterinary Medical Association) 

The name “distemper” is sometimes used to describe feline panleukopenia or feline parvovirus.  These are different than canine distemper and canine parvovirus.  This used to be a leading cause of death in cats, but very effective vaccines are available to prevent it.

The virus is virtually everywhere in the environment. It has appeared in all parts of the United States and most countries of the world. The virus can survive for up to a year in the environment, so cats may become infected without ever coming into direct contact with an infected cat. Young kittens, sick cats, and unvaccinated cats are most susceptible. It is most commonly seen in cats 3-5 months of age.