What it is
The virus passes through close contact: cats grooming each other, sharing bowls and litter boxes, through bites, and from a mother to her kittens. Young cats and kittens are hit hardest.
In some cats the immune system holds the virus down; in others it settles in the bone marrow and stays for life. It then disrupts the making of blood cells, so anaemia can develop and protection against infection weakens, and some cats develop lymphoma.
A blood test shows whether a cat is infected, which is worth knowing before a new cat joins the household. The virus does not pass to people or dogs. Ask your vet how to protect your cat.
Signs you may notice
A cat becomes listless, eats less and loses weight; its gums may be pale or inflamed and its lymph nodes swollen. Infections keep returning and are slow to clear.
When to see a vet
Book a visit if your cat is losing weight, has turned listless or keeps getting infections. If its gums suddenly turn pale or it struggles to breathe, a vet is needed immediately.
This is general information, not veterinary advice. For your own cat's health, tests and treatment, see a vet.