What is Cat Flu?
Understanding Cat Flu
Despite the availability of effective vaccines, cat flu remains relatively common. The disease can vary in severity, but kittens are particularly vulnerable, and entire litters have occasionally been lost to infection.
Which Cats Are at Risk?
Cat flu is most frequently seen in environments where cats are kept in large groups, such as breeding catteries, rescue centres, and feral colonies, though it can also affect household pets.
Cats most at risk include:
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Unvaccinated cats
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Kittens
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Elderly cats
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Cats with weakened immune systems
Symptoms of Cat Flu
Signs of cat flu may include:
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Sneezing and nasal discharge
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Conjunctivitis (red, inflamed eyes) and eye discharge
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Loss of appetite
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Limping, which may shift from one leg to another
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Fever and depression
Occasionally, cats may develop mouth or eye ulcers and drooling. Young, elderly, or immunosuppressed cats are more likely to develop severe disease, which can be fatal.
What Causes Cat Flu?
Cat flu is not related to human influenza. Unlike human flu, which is caused by a single virus, cat flu is a syndrome caused by multiple pathogens.
The primary agents include:
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Feline Herpesvirus (FHV)
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Feline Calicivirus (FCV)
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Bordetella bronchiseptica (a bacterium)
In households or catteries, cat flu may involve one or more of these pathogens simultaneously.
Feline Herpesvirus (FHV)
Most cats recover fully from FHV, but recovery can take several weeks, and some cats may experience long-term effects, including:
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Recurrent eye problems
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Chronic rhinitis (persistent nasal discharge)
Secondary bacterial infections can lead to chronic conjunctivitis, sinusitis, or bronchitis. Antibiotics may provide temporary relief, but FHV is a virus, not a bacteria.
Cats that are carriers may develop clinical signs after stressful events, such as boarding in a cattery, even months after the initial infection.
Feline Calicivirus (FCV)
FCV often causes a milder form of cat flu, sometimes with only mouth ulcers on the tongue, roof of the mouth, or nose. Some strains can lead to lameness and fever in young kittens.
Most cats recover within a few days, though pain relief may help during this period. Many cats become carriers, shedding the virus intermittently, while some develop persistent infections, which can be associated with chronic oral inflammation (gingivostomatitis).
Bordetella Bronchiseptica (Bb)
Better known for causing kennel cough in dogs, Bordetella bronchiseptica can also infect cats, producing respiratory signs similar to viral cat flu.
Young kittens are particularly at risk, and outbreaks can occasionally result in the loss of entire litters. Cats that recover may remain carriers, capable of transmitting the disease to other cats for years.