A potentially deadly cat virus that was initially detected in four Nanaimo felines in March has spread across the city, animal experts say.

Feline Immunodeficiency Virus (FIV) can reduce the effectiveness of a cat’s immune system to the point where the animal becomes very susceptible to different infections and cancers.

The contagious disease is often referred to as the feline version of HIV and is passed through blood transmission.

Since the story aired on CTV News last month, the BC SPCA Nanaimo Branch says it’s received numerous calls from concerned pet owners.

FIV was first identified in one neighbourhood in the Harbour City, but SPCA officials say it hasn’t been contained.

According to the Nanaimo branch, animal control completed a study and in the about 10 instances over the last 12 months FIV was detected in cats from as far as Uplands Drive and Rutherford all the way down to Cedar.

“A small sampling of 10 [cats] across the whole city suggests that there’s quite a few cats who are affected and there’s certainly a lot of cats who are at risk of exposure,” said Leon Davis.

There is a vaccine for the disease, but experts say it’s not effective.

“The only 100 per cent way to protect your cat from FIV is to keep your cat inside,” Davis said.

It can be difficult to detect whether a cat has been infected with the virus, and experts recommend outdoor felines with poor health get tested.

Experts also suggest building a "catio" for your pet if it’s accustomed to going outdoors.

The BC SPCA has posted a map showing the areas of Nanaimo where cats with FIV have been found.