Here is an excerpt from an article on Feline Viral Rhinotracheitis (FVR) (aka Feline Herpes Virus)

B) Latent and "Carrier" Disease

Eighty percent of all previously infected cats go on to become carriers of the disease. In so doing they become "latent" after recovering from the first infection. Latent is the term used for the presence of a disease organism that is not causing the disease at that particular time in that particular individual.

A "carrier" cat is one who has been previously infected (and has gone through the active phase of the disease) and is now recovered. All carrier cats are either active (currently undergoing active virus infection within their bodies) or latent (the virus is present, but not active). Carrier cats in the active phase can become ill again (although not always, and usually not to the same degree as the first time) and can shed (spread virus to the environment and other cats). Cats in the latent phase only have the virus internally, but feel normal and do not shed the virus to other cats and the environment.

What triggers a carrier cat to move from the latent to the active phase is STRESS. Any physical or emotional event in a cat's life can be considered stress including cat shows, moving, boarding, pregnancy, birthing, vaccinations, new family member (human or feline!), other diseases, injury, surgery, crowding, etc. An active phase, healthy looking carrier cat can shed as much virus to others and into the environment as a newly infected sick cat!

One week is the usual time frame from the triggering event to the production of active, shedding virus and possible illness. It will take another two weeks for the cat to get through this active phase. Sometimes the only sign of an "active" carrier cat with Rhinotracheitis is an eye ulcer, or swollen membranes around the eye, or mild, persistent sneezing.

How Do Cats Become Infected with Rhinotracheitis?

All cats must come in contact with the virus to become infected. This virus makes its entrance internally through the eyes, nose or mouth.


Direct Contact: Direct contact is from a sick or active carrier cat directly to another cat. In catteries, multiple cat households and shelters, the chances of this happening are high. Multiple, repeated infections may occur during the outbreak so that each successive infection produces more virus in each individual. Direct contact is by far the most common way for a cat to be infected with Rhinotracheitis.

Indirect Contact: When a cat sneezes and distributes virus to litter pans, furnishings, and food/water bowls, the environment in which it lives becomes infected. A cat coming in contact with these objects becomes infected indirectly rather than directly from the cat that put it there. People can also spread this virus from cat to cat on their hands and clothing. Indirect contact can be a source of infection in shelters, catteries or even veterinary clinics. The FVR virus itself does not live longer than 48 hours once it is outside the cat's body, but that is usually long enough to cause infection under some conditions. It is possible, of course, for a cat to get infected both directly and indirectly at the same time.

In utero: Unborn kittens can be infected by their mother while still in the uterus during pregnancy.
Infected kittens become sicker and shed more virus than adult cats. Accordingly, sick kittens are the worst source of infection to other kittens, who in turn will get even sicker and shed more virus than the ones who gave it to them. The younger the kitten (under six weeks of age) the greater the reaction and resulting infection.



This is the second part of this article regarding the Calici virus:

Once a cat or kitten has been infected with Calici virus, it will continue to spread it into the environment and to other cats even after recovery. There is no time limit to this, and it can continue for a few short weeks to as long as a few years.

Remember, a "carrier" cat is one who has been previously infected (and went through the active phase of the disease) and is now recovered. All carrier cats of Calici virus are active (currently undergoing active virus growth within their bodies) as there is NO latent form of this disease. In other words, recovered cats ARE carrier cats and can shed (spread virus to the environment and other cats) continuously.


How Do Cats Become Infected with Calici Virus?
All cats must come in contact with the virus to become infected. This virus makes its entrance internally through the eyes, nose or mouth, usually by coming in contact with a carrier or ill cat.


Direct Contact: Direct contact is from a sick or carrier cat directly to another cat. In catteries, multiple cat households and shelters, the chance of this happening are high. As the disease progresses from cat to cat, multiple, repeated infections may occur so that each successive infection produces more virus in each individual.
Indirect Contact: When a cat sneezes and deposits virus to litter pans, furnishings, and food/water bowls, the environment in which it lives becomes infected. A cat coming in contact with these objects becomes infected indirectly rather than directly from the cat who put it there. People also spread this virus from cat to cat from their hands and clothing. Indirect contact can be a source of infection in shelters, catteries or even veterinary clinics. It is possible for a cat to get infected both directly and indirectly at the same time, especially when living or boarding in the same place for a period of time with the infective cat. Calici virus can survive in the environment for 8 to 10 days, making indirect contact equally important with direct contact as a source of infection.