A: In general, most feline upper respiratory infections are caused by viruses that are specific to cats. These viruses are not contagious to other species, including dogs and people. Oftentimes, these viruses lead to bacterial sinus infections or conjunctivitis. Usually, these are simply overgrowth of normal cat bacteria that are always present in cats.
Bacteria can usually lead to infections in any species if it gets access to somewhere that it doesn’t belong, like a wound, eye, or respiratory tract. Therefore, it’s always a good idea to wash your hands after having close contact with any animal. However, a cat with an upper respiratory infection is usually not a higher risk than healthy ones.
There are some unusual infections that can indeed pass from cats to other animals or people. That’s part of why it’s important to see your family veterinarian any time your cat is sick. It’s part of our job to protect both animal and human health. A veterinarian really is your “other family doctor.”
If your veterinarian prescribes an antibiotic for your cat’s infection, it is important for the health of your family to use it exactly as prescribed for the full duration of treatment. Antibiotic resistance induced in cat bacteria can lead to anti-biotic resistance in human infections. This situation doesn’t even require direct exposure to cat bacteria, since different types of bacteria in the same environment can share genes that code for antibiotic-resistance. That’s why I cringe every time I hear, “I have some antibiotics left over from last time.”