FIV (Feline Immunodeficiency Virus)
According to Wikipedia,
Feline immunodeficiency virus (FIV) is a lentivirus that affects cats worldwide. From 2.5% up to 4.4% of cats worldwide are infected with FIV. FIV is not typically fatal for cats, as they can live relatively healthily as carriers and transmitters of the disease for many years.
FIV was first isolated in 1986 by Dr. Niels Pedersen at the UC Davis School of Veterinary Medicine in a colony of cats that had a high prevalence of opportunistic infections and degenerative conditions and was originally called Feline T-lymphotropic Virus (FTLV). It has since been identified in domestic cat populations worldwide.
FIV can be tolerated well by cats, but can eventually lead to debilitation of the immune system in its feline hosts by the infection and exhaustion of T-helper (CD4+) cells. In cats the percentage of this happening is very low. Less than 5%.
FIV and HIV are both lentiviruses. However, humans cannot be infected by FIV, nor can cats be infected by HIV. FIV is transmitted primarily through deep bite wounds, where the virus present in the infected cat's saliva enters the body tissues of another cat. FIV+ cats can share water bowls, pellet bowls, eat from the same bowl of wet food, and use the same litter box with low danger of transmitting the disease. A vigilant pet owner who treats secondary infections can allow an infected cat to live a reasonably long life. The chance that an FIV-infected cat will pass the virus to other cats within a household is low, unless there is fighting between cats, or wounds present that could allow entry of the virus from infected to non-infected cat.
Newborn kittens may test positive for up to six months and most thereafter will gradually test negative. It is thought that this is due to antibodies transferred to the kittens via the mother's milk. However, these antibodies are transient so subsequent testing will be negative.
The primary mode of FIV transmission is via deep bite wounds, where the infected cat's saliva enters the other cat's tissues. FIV may also be transmitted from pregnant females to their offspring in utero, however this vertical transmission is considered to be relatively rare based on the small number of FIV-infected kittens and adolescents. This differs from FeLV (Feline Leukemia), which may be spread by more casual, non-aggressive contact such as mutual grooming and sharing of food bowls.
Risk factors for infection are being of the male sex, adulthood, and outdoor access.
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In summary, FIV is an auto-immune disorder cats can get but humans cannot. It is primarily transmitted through bites and is usually found among outdoor, un-fixed males who are outside fighting each other for territory and dominance. Cats who live indoors their whole lives should be safe unless somehow bitten by an infected cat. FIV positive cats and negative cats can safely co-exist their entire lives together. You need to make sure these cats are safely and properly introduced and they get along just fine. (see our page on Introducing Cats) Humans are safe and cannot get FIV.
There are more and more articles coming out all the time with new information about FIV. Unfortunately, most of the public is going by old information on what people USED to think FIV was all about. Please help educate yourself and others about FIV.
Kittens often give a false positive to FIV on a combo test. They may still be nursing from a positive mom and this may result in an innacurate test result. It is recommended to retest the kittens at 6 months of age and almost always, they test negative for FIV from this point on. Here's some info about FIV and kittens:
https://www.alleycat.org/resources/protocols-testing-feline-immunodeficiency-virus-fiv-and-feline-leukemia-virus-felv/
Be sure to refer to your vet for more information.
Below are some more links to articles about FIV:
https://consciouscat.net/2010/07/12/fiv-separating-myth-from-fact/
https://pets.webmd.com/cats/cat-fiv-feline-immunodeficiency-virus#1
https://www.aspca.org/pet-care/cat-care/common-cat-diseases
https://resources.bestfriends.org/article/fiv-cats-faqs-feline-immunodeficiency-virus