Cat flu
The correct name for cat flu is Feline Respiratory Disease (FRD). It has nothing to do with the human flu virus. The first signs are often sneezing, followed by a watery eye discharge which gradually becomes thicker and yellow. If it is severe the eyes can become swollen and puffy and eventually ulcerated. The cat will usually stop eating as he has no sense of smell. The cat is also likely to develop mouth ulcers. All this is very painful and miserable for the cat and he is likely to become very depressed.
A different strain, caused by the feline calcivirus infection, often has ulcers on the cat's tongue as its first symptom. Ulcers can also appear on the cat's paws.
Your cat can develop bronchitis or pneumonia as complications of the disease.
PREVENTION IS BETTER THAN CURE! Get your cat vaccinated at the earliest possible opportunity. If your cat does develop the disease, get vet attention as quickly as possible and give him good nursing. Keep cleaning his nose and eyes with damp cotton-wool balls. Try to keep your cat eating by giving strong-smelling foods such as fish or cheese. Groom him to increase his sense of wellbeing.