Feline Upper Respiratory Infection (URI) is similar to a common cold in humans. It is especially common in cats who have been exposed to a lot of other cats, such as at an animal shelter. URI is very rarely fatal, and usually resolves within one to three weeks. Treatment generally consists of supportive care.
Antibiotics are sometimes given to treat possible bacterial infections. However, while secondary bacterial infections can make the problem worse, the underlying cause is often viral. Viral infections are not cured by antibiotics, so as with the common cold, there is no completely effective treatment besides time and allowing the cat's own immune system to do its job.
In rare cases, URI can cause serious disease such as pneumonia. Also, sick cats may not eat or drink enough thus becoming severely dehydrated. In such cases, hospitalization and fluid supplementation may be needed.
URI is contagious to other cats. Most cats are vaccinated against it (as part of the standard yearly vaccination program recommended by most veterinarians). However, the vaccine is not 100 percent protective, so it's a good idea to isolate cats who are showing signs of the illness, and wash your hands after handling sick cats.
In general we recommend you isolate all new arrivals in your household for eight to 10 days after adoption, to give them a chance to settle in and make sure they are not getting sick. Generally, URI is not contagious to healthy people nor to other animals.
First, it important to state that every animal adopted from a shelter should be taken for an examination by your regular veterinarian three to seven days after adoption. With rest and good care, many cats will recover from mild URI in one or two weeks. Sometimes cats need additional help. If your cat has any of the following signs, contact your veterinarian.
Information courtesy of the University of California at Davis Koret Shelter Medicine Program