Feline Herpesvirus (Cat Flu): Signs, Treatment, and Prevention

How it spreads

Infected cats shed the virus in discharge from the eyes, nose and mouth. It passes to other cats through close contact, sneezed droplets and shared objects such as food bowls, litter boxes, bedding and toys. People can carry it on their hands and clothes from one cat to another.

Signs usually appear two to six days after exposure. A cat can spread the virus before it looks sick and for up to about three weeks after signs start. The virus moves most easily where many cats live close together, such as shelters, catteries and multi-cat homes.

The virus infects only cats. People, dogs and other pets cannot catch it. It does not last long on skin, and most household disinfectants and detergents kill it, so regular cleaning of bowls, bedding and surfaces helps protect the other cats in your home.

Signs to watch for

Most signs show up in the eyes and nose. A cat may have one or several of these:

• Frequent sneezing
• Discharge from the nose, clear at first and later thick, yellow or green
• Red, swollen or watery eyes, often with discharge
• Squinting, blinking a lot or keeping one eye closed
• Fever, tiredness and hiding
• Poor appetite, often because a blocked nose means the cat cannot smell its food
• Drooling

Once signs appear, the illness usually lasts about 10 to 20 days. Severe cases can take longer. Herpesvirus is the most common cause of conjunctivitis, or pink eye, in cats. Some cats go on to have long-term eye problems, such as repeated ulcers on the surface of the eye, scarring or dry eye. A few are left with a chronic stuffy nose.

When it is an emergency

A vet visit is recommended for any cat with signs of cat flu. Some signs mean the cat should be seen the same day:

• Breathing with the mouth open, or breathing that looks like hard work
• A kitten that stops eating or nursing, or seems weak or cold
• An adult cat that has not eaten for a day or more
• Signs of dehydration, such as sunken eyes or dry, sticky gums
• A cloudy eye, an eye held shut, or obvious eye pain
• Extreme tiredness or collapse

Kittens are most at risk. In young kittens the infection is often more severe, and it can spread to the lungs and be fatal. Eye ulcers also need prompt care, because an untreated ulcer can damage the eye for good.

How vets diagnose and treat it

Vets often diagnose cat flu from the signs and a physical exam. To check for ulcers, they may put a harmless dye on the eye that makes damaged areas glow under a blue light. To confirm the virus, a vet can take swabs from the eye, nose or throat for a PCR test. Carriers shed the virus on and off, so a negative result does not always rule it out. Blood antibody tests cannot tell infection apart from vaccination, so they are of little use here.

There is no treatment that removes the virus from the body. Care supports the cat while its immune system fights the infection. Depending on how sick the cat is, a vet may give fluids for dehydration, help with feeding, or in severe cases place a feeding tube. Saline nebulizing or saline nose drops can help loosen thick mucus. For eye ulcers or severe illness, vets may prescribe antiviral eye drops or ointment, or antiviral medicine by mouth. Antibiotics have no effect on the virus itself. Vets prescribe them when bacteria cause a second infection on top of it, which is common.

Lysine supplements were widely suggested for cats with herpesvirus in the past. Current guidance from European feline specialists finds no good evidence that they help, so ask your vet before giving any supplement. Steroid medicines can reactivate the virus, and some human medicines are toxic to cats, so give only the medicines your vet prescribes.

Caring for your cat at home

Good nursing helps a cat recover. Gently wipe away discharge from the eyes and nose several times a day with a soft cotton pad moistened with warm water, using a fresh pad for each eye. Moist air can help loosen mucus, so ask your vet whether humidifying the room or short sessions in a steamy bathroom would help your cat.

Cats rely on smell to decide what to eat. Slightly warmed, strong-smelling wet food can tempt a cat with a blocked nose. Offer small amounts often and keep fresh water close by. Keep the cat warm, quiet and indoors, away from other cats, and wash your hands after handling it. If your cat still refuses food, tell your vet, because cats that go without food for long can become seriously ill.

Carriers and flare-ups

After the first infection, the virus hides in nerve cells in the head and stays there for life. Almost every infected cat becomes a carrier. Most of the time the virus is quiet and the cat is healthy.

Stress can wake the virus up. Common triggers include moving to a new home, boarding, a new pet in the home, illness, injury or surgery, steroid medicines, and giving birth or nursing kittens. When this happens, the cat sheds the virus again. Some cats show mild signs such as sneezing or a runny eye. Others shed the virus with no signs at all and can still infect other cats.

Steady routines, safe hiding places and slow introductions to changes can lower the chance of flare-ups. If flare-ups keep coming back or involve the eyes, talk to your vet about a plan.

Vaccination and prevention

The feline herpesvirus vaccine is a core vaccine, which means it is recommended for every cat, including indoor cats. It is usually given in a combined vaccine that also covers calicivirus and panleukopenia.

Vaccination reduces how sick a cat gets and can reduce how much virus it sheds. It does not always prevent infection, and a vaccinated cat can still become a carrier. Kittens usually get their first dose at 6 to 9 weeks of age, then further doses every few weeks until about 16 weeks of age, followed by a booster six months to a year later. After that, adult cats are usually given boosters every one to three years, depending on their risk. Cats in shelters, boarding or busy multi-cat homes may be boosted more often. Your vet will set the schedule that fits your cat.

Kittens get some protection from their mother's first milk, but in some kittens it is gone by six weeks of age, before the vaccine series is finished. A mother cat that carries the virus can also pass it to her litter, because giving birth and nursing can wake the virus up. Keeping young kittens away from unknown cats helps. When you bring home a new cat, keep it apart from your other cats for at least one to two weeks, or longer if your vet advises. Use separate bowls, litter boxes and bedding, and wash your hands between cats.

Cats from rescues and shelters

Cat flu is very common in rescued kittens and in cats from shelters. In large groups of cats, up to half may be shedding the virus at a given time. A move to a new home is also a well-known trigger, so a newly adopted cat may start sneezing or get runny eyes in its first days or weeks with you, even if it looked well before.

These flare-ups are often mild and pass, but a vet check is a good idea, especially for kittens or if the eyes are affected. At Paw Squadron, the first stops after every rescue are the vet and a bath. Every animal gets a checkup, treatment, vaccinations and a microchip before adoption. Vaccination lowers the risk of severe illness, but a cat that already carries the virus can still have flare-ups later in life. Bring your cat's vaccination record to the first visit with your own vet.

If you are thinking about adopting a cat, the Adoptions page shows the animals looking for homes, and the FAQ answers common questions about the process.