Why does my cat sneeze? (cat flu)

A sneeze is the nose clearing something out. A single sneeze, or a short run of them after a tickle from dust, is normal and passes within minutes.

Sneezing is a sign that the lining of the nose is irritated. It is not a disease by itself, so the cause matters more than the sneeze.

How often the cat sneezes, what comes out of the nose and eyes, and whether the cat is still eating and playing tell you more than one sneeze does.

Cat flu is an umbrella name for several infections of the upper airways that cause sneezing and discharge. It is not one single disease, and it is not related to human influenza.

Two viruses, feline herpesvirus and feline calicivirus, cause about 90 percent of cat flu, often with bacteria such as Chlamydia felis, Bordetella bronchiseptica and Mycoplasma felis on top.

Herpesvirus mostly hits the eyes and nose, sometimes with ulcers on the surface of the eye. Calicivirus tends to cause mouth ulcers, most of all on the tongue, and milder eye signs.

Irritants are a common reason for occasional sneezing: dust, dusty litter, perfume, cigarette smoke, scented candles, essential-oil diffusers, cleaning products, mould and pollen.

Cats can have something like hay fever (allergic rhinitis). It is often not clear what bothers the nose, so an owner who suspects an allergy can ask the vet.

Infection is the other big group. Cat flu is the best known, but dust and infection can look alike at first, which is why the extra signs matter.

A grass blade, seed or bit of litter can lodge in the nose or throat. This gives sudden, frantic sneezing fits, often from one nostril, and the vet has to remove it under anaesthetic.

Dental disease can show up in the nose, because the roots of the upper teeth sit just under the nasal passages. An infected tooth root can drain into the nose and give a runny nostril, sometimes on one side only.

Polyps are benign growths that mostly affect younger cats and can look like an infection. Tumours in the nose are more likely in middle-aged and older cats, and only a sample can tell what a growth is.

Rarer causes include a fungal infection (Cryptococcus), caught by breathing in spores from bird droppings or rotting plants. It gives a nasal discharge that lasts and may turn bloody. Bacterial infections such as Mycoplasma or Bordetella can cause sneezing with very smelly snot, or snot with blood in it.

Discharge from both nostrils usually points to something widespread, such as a virus or an allergy. Discharge from one nostril only points to something local, such as an object, a tooth or a growth, even if the cat seems fine.

A cat that was given a cat flu vaccine as nose drops may sneeze often for 4 to 7 days afterwards.

The viruses spread by direct contact with an infected cat: tears, saliva, nasal discharge and the droplets of a sneeze. They also spread on bowls, litter trays, bedding, grooming tools, hands and clothing.

Signs usually start 2 to 6 days after contact, though some sources say up to 10 days.

How long the viruses last outside the cat differs between sources. Herpesvirus survives for a short time, up to about two days. Calicivirus lasts longer: from several days to a month on dry surfaces.

Most cats that recover become carriers. They look well but can still shed virus in saliva, tears and nasal discharge.

Herpesvirus stays in the body for life, hidden in the nerves of the face. Stress, a move, a new pet, boarding, surgery or steroid medicine can wake it up, and the cat starts sneezing and shedding virus again, often about a week later.

Calicivirus is shed continuously in many infected cats. Most stop within weeks to months, but a minority keep shedding for years.

A cat that looks healthy can pass the virus on. In one shelter study 31 percent of cats that tested positive for the viruses had no signs at all. Up to 97 percent of cats meet herpesvirus at some point in life, most of them as young cats.

Kittens, elderly cats, cats with a weak immune system (for example with FIV or FeLV) and stressed cats get the most severe illness. Flat-faced breeds such as the Persian are more likely to have lasting nose problems.

The more cats share a space, the more cat flu there is. Shelters, rescue centres, breeding catteries, boarding catteries and feral colonies carry the highest risk. Calicivirus infects about 10 percent of cats in small groups and up to 90 percent of cats in crowded places such as shelters.

In a shelter study about 4 percent of cats were shedding herpesvirus when they arrived, and about half were shedding it one week later, both from old infections waking up and from new ones. Many cats are already carrying the virus when they are adopted, even when they show no signs, and a move to a new home is stressful enough to wake it up.

When cats with signs are isolated but cats without signs are mixed in straight away, infection keeps spreading from cats that look healthy. In a home with several cats, several ill cats at once is a reason to call the vet at once, because outbreaks spread fast.

A rare, severe form of calicivirus has caused outbreaks with swelling of the head and legs, sores, yellow skin and bleeding. It has killed up to about two thirds of affected cats.

Typical signs are sneezing, a runny nose, watery or sticky eyes, red eyes with a lot of blinking, drooling, tiredness, fever and eating less. A cat can have a few of these or all of them.

The nose discharge often starts clear and watery and later turns thick. Eye discharge from Chlamydia starts clear and later becomes thick, yellowish and pus-like.

Sores on the tongue, palate or lips are typical of calicivirus. They hurt, and the cat may drool.

Many cats stop eating, because a blocked nose takes away the sense of smell and mouth sores make eating sore.

A cough and fast breathing can mean the infection has reached the lungs. This is most serious in young kittens. Kittens with calicivirus can limp for a few days, and the limp usually passes without treatment.

Mild cases in healthy adults fade over one to two weeks. Most colds run their course in 7 to 10 days, though some sources allow up to three weeks.

Sneezing with a cough can mean a lower airway problem, not just a runny nose. Tell the vet about it.

Cats nearly always breathe through the nose. A cat that breathes with an open mouth, struggles to breathe or collapses needs a vet straight away. Fast breathing at rest, above about 35 breaths a minute, is a sign of lower airway disease. It needs a vet.

Sneezing together with coughing, retching or eating less is a reason for a vet visit, and so is sudden violent sneezing that may mean something is lodged in the nose or throat.

A short snorting fit that sounds like the cat is breathing in sharply (a reverse sneeze) is, in most cats, a harmless reflex that passes within seconds. Frequent episodes still deserve a vet check.

In kittens, Bordetella can spread to the chest and has a relatively high death rate.

A vet usually works out cat flu from the signs, after looking at other causes. A swab from the eye, nose or mouth for a PCR test is used when the cat is very ill, signs do not settle, or in an outbreak.

A positive PCR test can come from a cat that only carries the virus, so the result has to be read next to the signs. One negative result does not rule cat flu out.

Treatment is mostly supportive: keeping the cat comfortable, hydrated and eating while the body fights the infection. A mildly affected healthy adult may need no medicine.

Vets commonly give antibiotics when a bacterial infection is on top of the virus, not for the virus itself. They may use antiviral eye treatment for herpesvirus eye ulcers, and antiviral tablets in severe or long-lasting cases. There is no antiviral that clearly works against calicivirus.

Other things a vet may add are eye drops or ointment, pain relief for sore mouths, saline or nebulising to loosen mucus, and fluids for a cat that is dehydrated.

A cat that will not eat may be offered soft, strongly smelling food, gently warmed. Some cats need hand feeding, and some need hospital care with a drip and a feeding tube.

At home the usual advice is to keep the cat warm and quiet, with food, water, a litter tray and a bed close by. Wipe discharge from eyes and nose gently with a damp cloth or cotton wool. A steamy bathroom can ease a blocked nose; stay with the cat near hot water.

Vets advise asking before you try any home treatment or medicine, because some are harmful to cats. Lysine supplements do not cure cat flu. Studies are mixed, and a shelter study found they may make signs and shedding worse.

If sneezing lasts, is on one side, or is bloody, a vet may look at the teeth and inside the nose, and may use X-rays, CT or a small camera (rhinoscopy), often under sedation or anaesthetic.

Treatment of the other causes depends on what is found: an object in the nose is removed under anaesthetic, dental disease needs dental care, and a growth is checked with a sample. Most cats recover over several weeks. Some are left with a runny nose or sneezing that keeps coming back and is managed rather than cured.

Vaccination against herpesvirus and calicivirus is part of the core vaccines that WSAVA advises for every cat. It lowers the risk and usually prevents severe disease, but it does not always stop infection or virus shedding. A vaccinated cat can still sneeze with cat flu, usually in a milder form. The herpesvirus and calicivirus vaccines protect less strongly than the one against panleukopenia.

A cat that has had cat flu is not protected for life, so vaccinating recovered cats is advised. Chlamydia and Bordetella vaccines are not given to every cat. The vet decides from the cat's life, for example a shelter or boarding stay. A vaccine given as nose drops can protect within 3 to 4 days, and vets sometimes choose it for cats that go into shared housing.

Keep a cat with signs in one room, with its own bowls and litter tray and surfaces that are easy to clean. A cat can still spread virus after the signs stop, so ask the vet when it can rejoin the others. Wash your hands after handling a sick cat, its bowls or its litter, and clean litter trays daily. Care for healthy cats first and the sick cat last.

Herpesvirus is killed by most disinfectants, but calicivirus resists many of them, so cleaning has to be thorough. Bleach-based cleaners are named as working on both; ask your vet which product to use.

Before you bring a cat home, look for sneezing, watery eyes or a runny nose, and keep the new cat apart for the first week or longer. One source advises about three weeks of quarantine in a home with other cats.

Stress wakes up herpesvirus. Calm routines, hiding places, gradual introductions and fewer cats in each group all help. To protect the nose from irritants, avoid smoke, aerosols, diffusers and scented candles, and consider a low-dust litter. Keeping a cat indoors reduces its contact with the fungus behind some chronic nose disease and with objects such as grass seeds.

The cat flu viruses (herpesvirus and calicivirus) are not known to infect people, and a cat cannot catch human flu.

Rare bacterial species involved in cat flu can affect people with a weak immune system. People who are immunocompromised or pregnant are advised to avoid cleaning litter trays where possible.

A dog or other pet does not carry the cat's viruses. Bordetella is the exception: infected dogs can pass it to cats.

You can carry virus to another cat on your hands or clothes after touching a sick cat.