My cat's FCoV test: positive antibody, negative antigen. Is she sick?
Good question. This is a complex disease that most cats are exposed to. Most cats that are just exposed but don't end up sick with the disease are going to come up positive for antibodies against the virus. However, a pet is only confirmed to have this disease if they have positive Antigens. Therefore, since your pet Sonia had a positive antibody and negative antigen, this means she was exposed to the virus, but has not developed the full blown disease. With this said, cats can at any point do what is called seroconvert to the active strain of the virus and become sick since they are carriers of the gene. If your pet becomes sick in the future, rechecking the antigen levels is highly recommended.
Because your pet is a carrier for Coronovirus (FCoV), loose stool may be seen, but nothing more severe than that.
Here is more information on Coronavirus (FCoV) in pets and also information on how pets can seroconvert into full blown FIP (FIPV) from exposure to this virus.
---> https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4951308
---> https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4951549
Updated on September 23rd, 2025