Cat flu in cats in India: which virus does what, why a recovered cat carries it for life, and what the vaccine actually promises

Signs of Cat flu (feline upper respiratory tract disease)

The 10 signs to watch for are listed below. Any one of them is a reason to consult your nearby vet; none of them is a diagnosis.

• Sneezing in bursts, usually the first thing an owner notices
• Runny eyes and a runny nose, watery at first and thicker later
• Red, swollen eyelids, sometimes gummed shut in the morning
• Ulcers on the tongue or the roof of the mouth
• Drooling and refusing food because the mouth is painful
• Fever, hiding and flat, quiet behaviour for the first few days
• Squinting, or a dull or cloudy patch on the eye surface
• Shifting lameness with fever, a different leg each day
• Loss of smell, so the cat stops eating food it cannot smell
• Noisy or open-mouth breathing, which is never normal in a cat

Breeds on this site that document this condition

Each breed page below carries the figure for this condition with its denominator and its source. The 5 breeds listed are the ones on this site that document it, not a ranking of risk.

Cat flu is two unrelated viruses, and they leave different marks

Cat flu is the everyday name for feline upper respiratory tract disease, and in most cases it results from infection with feline calicivirus (FCV) or feline herpesvirus (FHV). The two viruses are not related to each other, neither is an influenza virus, and they damage different tissue. Getting the split right is the whole job, because it tells you which sign to watch and what the cat is likely to be left with.

Feline herpesvirus-1 is the eye virus. After entering through the nose, mouth or conjunctiva it replicates in the lining of the upper airway and the eye, and viral replication is associated with conjunctivitis, ulcerative keratitis and rhinotracheitis. A dendritic ulcer on the cornea, a branching scratch pattern that only shows up under fluorescein stain, is considered pathognomonic for acute herpesvirus infection, which means nothing else produces it.

Feline calicivirus is the mouth virus. Oral ulcerations, sneezing and a serous nasal discharge are its main signs, the ulcers sit mainly on the tongue, and the anorexia and drooling that follow the mouth pain are often more prominent than any sign of rhinitis. A tongue ulcer is painful enough that a cat will sit over its bowl and refuse to eat from it.

The incubation figures disagree and both are worth carrying. ABCD puts the incubation period for acute calicivirus disease at 2 to 10 days, while the Merck Veterinary Manual gives 2 to 6 days for both feline viral rhinotracheitis and calicivirus and 5 to 10 days for pneumonitis. In practice that means a kitten brought home on a Sunday can start sneezing any time up to the second weekend, and a quiet first week proves nothing.

Why cat flu stays a useful phrase even though it names the wrong thing

The phrase survives because the two viruses turn up together so often that separating them at the door is not possible. In a UK cohort of 430 pet cats swabbed by their own owners, feline calicivirus was present in five of the nine herpesvirus-positive cats, a co-infection rate of 44 percent, and in three of the five cats positive for Chlamydia felis. In a southern Brazilian series of 120 cats with upper respiratory signs, co-infections affected 64.45 percent of cases.

Other organisms join in and change what a swab finds. Chlamydia felis, Mycoplasma felis and Bordetella bronchiseptica can be responsible for some of the respiratory signs rather than the calicivirus itself. A Shanghai survey of 374 urban stray cats found Mycoplasma felis in 70 of them (18.72 percent) and Chlamydia felis in 44 (11.76 percent), both well ahead of feline calicivirus at 14 of 374 (3.74 percent) and feline herpesvirus at 13 of 374 (3.48 percent).

How long cat flu lasts, and what the days actually look like

Acute cat flu usually resolves within 10 to 14 days, although ocular signs in cases of keratitis can persist longer. Calicivirus signs usually resolve after a few days with only symptomatic treatment, and the Merck manual puts the milder cases at 5 to 10 days. Two clocks keep running after that, and neither is visible to the owner.

The first clock is the illness. It opens with fever, frequent sneezing, nasal discharge that is either mucopurulent or watery, conjunctivitis, rhinitis and salivation, and the fever tends to fluctuate rather than hold. Appetite goes before anything else does, partly because the nose is blocked and a cat that cannot smell food will not eat it.

• Days 1 to 3. Fever, sneezing, watery eyes and nose, a flat and hiding cat that stops eating.
• Days 3 to 6. Discharge thickens as secondary bacteria arrive, eyes may gum shut, mouth ulcers show if the cat has calicivirus.
• Days 5 to 10. Milder cases start turning, appetite returns before the sneezing stops.
• Days 10 to 14. Acute disease has usually resolved, though eye signs can run on.
• Beyond 14 days. A cat still sneezing at three weeks is a chronic rhinosinusitis conversation, not a longer flu.

The limping syndrome runs on its own short clock. An acute transient shifting lameness with fever can accompany calicivirus infection, the lameness can be severe and can move quickly from one limb to another, and full recovery usually occurs within 24 to 48 hours without treatment. Owners who have not been warned about it reasonably assume the cat has been hit by something.

The two clocks that keep running after the cat looks well

The shedding clock. On recovery from calicivirus, many cats continue shedding, most of them for at least 30 days after infection, and a few for several years up to life-long. Herpesvirus behaves differently: during latency the virus is not shed at all, and shedding restarts only when something reactivates it.

The environment clock, where the sources disagree. International Cat Care says the viruses may survive in the environment and on objects for up to 2 days for herpesvirus and 10 days for calicivirus. ABCD says calicivirus survives in the environment and remains infectious for up to one month on dry surfaces at room temperature, and even longer in colder conditions. Both were read on 27 September 2026, both are current, and the longer figure is the one to clean to.

That gap is not academic in an Indian household where a rescued kitten shares a balcony, a carrier basket and a food bowl with a resident cat. Cleaning to the two-day figure and cleaning to the one-month figure produce very different routines.

Why a recovered cat carries feline herpesvirus for the rest of its life

A cat that recovers from feline herpesvirus does not get rid of it. The virus travels along the sensory nerves to the neurons of the trigeminal ganglia, which are the main sites of FHV latency, and ABCD states that it is thought that all cats experiencing primary infection are likely to become lifelong latent carriers. This is the single fact that reframes a recurring infection as one virus the cat already has.

That sentence deserves reading exactly as written. ABCD hedges it twice, with *it is thought* and *likely*, and attaches no denominator, because latency cannot be measured directly: there are no direct diagnostic methods to identify latency, since the virus persists as genomic DNA in the nucleus of latently infected neurons without replicating or shedding. Anyone quoting a clean percentage of cats that become carriers is quoting something the guideline does not say.

What has been measured is reactivation, and those numbers do carry denominators of a sort. Virus shedding can be induced experimentally in approximately 70 percent of latently infected cats following glucocorticoid treatment, and other reactivating stressful events include lactation at 40 percent and moving the cat into a new environment at 18 percent.

Some adult cats show acute clinical signs at the moment of reactivation, and that disease is called recrudescence; reactivation without any clinical signs is also observed. So a cat can be spreading virus to a new kitten in the house while looking entirely well.

Calicivirus persists by a different route. Healthy cats can be feline calicivirus carriers, and in those cats the virus is localised mainly in the retropharyngeal area close to the tonsils; in an experimental setting, tonsillectomy did not eliminate the carrier state, which suggests some virus also sits outside the tonsils. A small proportion of cats were found to be non-shedders despite continuous exposure over long periods, probably through immune-mediated or genetic host factors.

How many cats around yours are carrying it right now

In a UK cohort of 430 pet cats sampled by their own owners, 2.1 percent (9 of 430, 95 percent confidence interval 1.0 to 3.9) were positive for herpesvirus, 13.3 percent (57 of 430, 95 percent confidence interval 10.2 to 16.8) for calicivirus and 1.2 percent (5 of 430) for Chlamydia felis. Those are ordinary pet cats in ordinary homes, not a clinic caseload.

Both viruses are contagious enough that density, not luck, is the variable that moves the number. Calicivirus prevalence is lowest in healthy household cats kept in groups of fewer than four cats, at 2.5 percent, and higher in groups of four or more, at 32 percent, while prevalence within individual colonies and shelters ranges from low to 50 to 90 percent. For herpesvirus, prevalence of shedding is usually under 10 percent in healthy small populations and up to 50 percent in large ones, with the highest positivity rates of 25 to 50 percent found when cats with acute upper respiratory disease are sampled.

The sources also disagree, and the disagreement is really about which instrument was used. A study of 151 stray cats in Italian colonies found 85 percent antibody-positive for calicivirus and 70 percent of 669 feral, stray and community cats in Australia had neutralising antibodies, while only 1.4 percent of 347 urban stray cats in Shanghai were found to be shedding calicivirus RNA. Antibody answers *has this cat ever met the virus*; RNA answers *is this cat shedding it today*. They are not the same question and they should not be read as one.

For scale against the whole cat population rather than a swab study, upper respiratory tract disorder was recorded in 406 of 18,249 UK cats (2.2 percent) in one year and conjunctivitis in 302 (1.6 percent), and in a UK swab cohort purebred cats carried calicivirus at 2.48 times the odds of crossbreds (95 percent confidence interval 1.37 to 4.49). Those two studies used different years and different disorder taxonomies, so read them side by side rather than as one trend. The shelter number is the one that matters for a rescued Indian kitten. Four percent of cats are herpesvirus shedders on entering a shelter, and after one week that rises to 50 percent, which reflects both new infections in naive cats and reactivation in latently infected ones.

Cat flu is not influenza, and on Google India that confusion has two separate versions

Cat flu is not caused by an influenza virus. It results from feline calicivirus or feline herpesvirus, neither of which is related to the viruses that cause flu in people, and the resemblance is in the runny nose and nothing else.

The confusion is visible on the search results themselves. On 27 September 2026, reading the Google India results for the bare query, the second result was the United States Centers for Disease Control page about influenza in animals, and on the India-specific query a Facebook post about the first case of bird flu in domestic cats in India ranked sixth. An owner whose cat is sneezing lands on avian influenza content twice in ten results.

There is a clean positive test against that reading. The Shanghai stray-cat surveillance screened 374 ocular, nasal and oropharyngeal swabs for six respiratory pathogens including influenza A virus, and influenza A was not detected in a single sample, while 146 of the 374 were positive for something else. Cats do occasionally get influenza viruses, but they are not what cat flu means.

The Indian version of the confusion is a different disease entirely

In India the most widely read piece of journalism carrying the phrase is a Times of India Kolkata report of 21 October 2025 headlined *Cat flu turns fatal, vets pin hope on early diagnosis*. It opens by describing "a feline flu caused by a type of haemoprotozoa, or blood protozoa, and spread by infected ticks", lists loss of appetite, severe lethargy, anaemia, vomiting, dehydration and bloody stool as the symptoms, and quotes one veterinarian as seeing 25 to 30 cases of feline tick fever daily.

That is not cat flu. It is a tick-borne blood parasite, and it has exactly the Indian evidence base that herpesvirus and calicivirus do not. Three hundred and ninety domestic cats were screened at the Veterinary Clinical Complex of Bihar Veterinary College and three private clinics in Bihar, 90 showing compatible signs went forward for examination, and Cytauxzoon was confirmed in 24 of the 90 microscopically (26.66 percent) and 34 of the 90 by molecular testing (37.77 percent). The authors conclude that the infection has reached the domestic cats of Bihar, an area where it was not previously expected.

The last version of the question is whether any of it reaches people. For the real cat flu viruses the answer is settled: ABCD states that there is no evidence of feline herpesvirus infecting humans. A person nursing a sneezing cat is not at risk from the cat's virus, though ordinary hand washing still matters because hands and clothing carry the virus between cats.

How cat flu is diagnosed, and why a positive PCR does not settle it

To diagnose cat flu, a veterinarian works from the signs and the household situation first, and adds PCR on a conjunctival, corneal or oropharyngeal swab when the result will change what happens next. The test is useful and it is also easy to over-read in both directions.

The preferred method for detecting herpesvirus is PCR performed in a diagnostic laboratory, run on conjunctival, corneal or oropharyngeal swabs, corneal scrapings, aqueous humour, corneal sequestra, blood or biopsy specimens, and real-time quantitative PCR is the routine choice for its sensitivity and the quantitative result it gives. Calicivirus is best detected by reverse-transcriptase PCR.

Both directions of error are documented. A negative calicivirus RT-PCR result does not rule out infection, and healthy cats can test positive. For a cat with classic signs the swab often adds nothing; for a multi-cat house deciding whether to separate animals, it can add a great deal.

There is a third trap that matters wherever modified live vaccines are used, which is everywhere. A Thai study of 184 cats detected a vaccine-like calicivirus variant in one cat, and the ABCD guideline notes that RT-PCR or sequencing of calicivirus cannot be used to confirm or rule out virulent systemic disease, because the clinical signs and the epidemic situation have to be weighed as well.

The tests an Indian clinic will and will not have

Government teaching hospitals publish their rate cards, which is the most reliable way to see what is actually available. The list below was read live on 27 September 2026 and every figure was divided by 84.38 and by 74; none of them resolves to a round dollar amount, so none is a converted foreign price.

One line in that table is missing on purpose. The Bihar Veterinary College PCR menu names Parvo, canine distemper, PPR, Brucella, the Theileria, Babesia and Anaplasma panel and feline Cytauxzoon, and it names no herpesvirus and no calicivirus test at all. The most expensive feline PCR on an Indian government list is for the tick-borne disease the Kolkata newspapers called cat flu, and the test for the actual cat flu viruses is not on the list. That is the practical Indian answer: expect a clinical diagnosis, not a laboratory one.

For the eye, the cheap test beats the expensive one. Fluorescein staining is what reveals an ulcer, and the branching dendritic pattern it exposes is regarded as pathognomonic for acute herpesvirus. Any cat with a squint, a held-shut eye or a dull patch on the cornea should have that stain put in before anything is dripped into the eye.

Treatment for cat flu in general terms, and the supplement the evidence turned against

Treatment for cat flu is mostly supportive, because no drug clears either virus from the cat. Purina India's own page states that there is currently no single curative treatment and that antibiotics help only with certain complications, and that is the honest position. What a veterinarian adds is hydration, pain relief for an ulcerated mouth, antibiotics where secondary bacteria have taken hold, and an antiviral in selected herpesvirus cases.

Supportive care is not a consolation prize. In moderate cases it is the whole of the treatment, and the parts that make the difference are nursing parts. Getting food into a cat that cannot smell, getting fluid into one that has stopped drinking, and keeping the eyes and nose physically clear are what move the case, and an Indian clinic will price the fluid line at Rs 150 plus tax on the ICAR-IVRI rate card.

Antibiotics have a place and it is a narrow one. Both viruses are viruses, so an antibiotic does nothing to them; it is aimed at the bacteria that colonise damaged airway lining afterwards, and at organisms such as Chlamydia felis and Mycoplasma felis that genuinely respond to it. Dosing and choice are decisions for the veterinarian who has the cat in front of them, and this page prints no doses for anything.

Antivirals exist for herpesvirus and the evidence for them is real but modest. In a randomised, placebo-controlled trial in two United States shelters, 22 cats with upper respiratory signs were split evenly between famciclovir and placebo, herpesvirus DNA was detected in 11 of 21 cats sampled, and the risk of a worsening clinical score with each day of treatment was significantly lower in the famciclovir group than in the placebo group, at a p value of 0.006. Twenty-two cats is a small trial and the authors say so, calling for further pragmatic studies.

Lysine: what the evidence says, and when it changed

Lysine is the supplement almost every cat owner is offered, and the evidence has moved decisively against it. When Bol and Bunnik published their systematic review in 2015, lysine supplementation was recommended by more than 90 percent of veterinarians in cat hospitals. They reviewed seven studies on lysine and feline herpesvirus 1, two of them in vitro and five in cats, plus ten publications on lysine and human herpesvirus 1.

Their conclusion was blunt. There is evidence at multiple levels that lysine supplementation is not effective for the prevention or treatment of feline herpesvirus 1 infection in cats, lysine has no antiviral properties, it does not antagonise arginine in cats, in vitro work showed no effect on the replication kinetics of the virus, and several clinical studies found no benefit while some reported increased infection frequency and disease severity in cats receiving lysine. The recommendation printed in the paper is an immediate stop to lysine supplementation because of the complete lack of any scientific evidence for its efficacy.

The guideline position followed. ABCD states that because of lack of efficacy, l-lysine supplementation is not recommended for preventing herpesvirus re-excretion, that Cave and colleagues found the virus was not inhibited at any l-lysine concentration studied in vitro, and that l-lysine supplementation might potentially affect a kitten's growth by inducing arginine deficiency, as has been demonstrated in puppies.

None of that makes lysine dangerous for an adult cat in the way a wrong drug would be; no side effects have been published. It makes it ineffective, which matters because money and owner attention spent on it are money and attention not spent on the eye that needs staining.

What the cat flu vaccine actually promises, in the guideline's own words

The core cat flu vaccine reduces disease and does not prevent infection, and WSAVA says so in plain language. Vaccines intended to protect against FHV and FCV cause seroconversion but may only provide partial protection against disease and do not protect effectively against infection or development of the carrier state. Overpromising here is what destroys an owner's trust in the whole vaccination schedule, so it is worth quoting exactly.

WSAVA goes further in the same document. The protection afforded by the core FCV and FHV vaccine components will not match that provided by the panleukopenia vaccine, it is still possible for infection and disease to occur in fully vaccinated adult animals, and there is no FHV vaccine that can prevent infection. ABCD puts the calicivirus half in one sentence: vaccination usually protects from disease but not from infection.

The cleanest evidence for what that means over time comes from a controlled challenge trial. Cats given a primary course and a revaccination one year later were challenged three years afterwards with a virulent heterologous calicivirus strain and then a virulent herpesvirus strain. Vaccination produced a significant reduction in the severity of disease after the herpesvirus challenge and in the frequency of cats showing severe calicivirosis, but viral shedding was not reduced three years after revaccination, as opposed to the significant reduction in excretion seen a few weeks after primary vaccination and even one year after it.

Read that as two separate promises with two different shelf lives. The disease promise held for three years. The shedding promise did not.

Field data still shows the vaccine paying for itself. In a study of 184 cats across regions of Thailand, calicivirus detection was notably less likely in vaccinated cats, with an odds ratio of 0.22 (95 percent confidence interval 0.07 to 0.75, p equals 0.015). A vaccinated cat in that population was substantially less likely to be carrying the virus, which is a real effect even though it is not the zero an owner might have imagined.

What that means for the booster decision, and where India disagrees with the guideline

WSAVA's recommendation for adult low-risk cats, meaning solitary indoor animals that do not visit boarding catteries, is revaccination with modified live core vaccines at intervals of three years or longer, while for higher-risk cats more frequent revaccination to protect against calicivirus and herpesvirus, up to annually, may be warranted, and a calicivirus and herpesvirus vaccine can be given one to two weeks before the main annual visit to a boarding cattery. The 2020 AAHA and AAFP guidelines place the same three antigens in the core category for all cats, with non-core vaccines assigned on an individual risk assessment.

Indian practice does not follow the three-year default. Vetic, a clinic chain operating across Indian metros, prints on its own national cat vaccination page that cats once infected with feline calicivirus or rhinotracheitis virus will remain hosts for life and that adult cat vaccination with CRP is therefore always recommended annually, pricing the adult annual CRP and anti-rabies visit from Rs 1,899 and the three-visit kitten course from Rs 3,999, read live on 27 September 2026. Half of that reasoning is sound and half overstates the evidence: lifelong carriage is the documented pattern for herpesvirus, while for calicivirus most cats shed for at least 30 days and only a few for years up to life-long.

Where the guideline and the clinic genuinely differ is on risk, not on biology. A cat that meets other cats, boards, or lives in a house that keeps taking in rescues is a higher-risk cat by WSAVA's own definition, and annual revaccination is what WSAVA recommends for it. A single indoor cat in a closed flat is the case where three years is defensible.

One shortcut does not work. You cannot titre-test your way past this decision, because the presence of antibody against FHV or FCV is not currently considered a reliable predictor of immune protection against either virus, and tests for anti-FPV antibodies are considered more reliable indicators of protection in cats than tests for anti-FHV and anti-FCV antibodies. A titre result can tell you about panleukopenia and cannot tell you about cat flu.

Breeding households hit a wall of their own. Vaccinating the queen to prevent infection of her kittens is not effective, because vaccination does not prevent the development of carrier status, although a queen with a good antibody titre passes high levels of maternally derived antibody in the colostrum that protect the kittens through their first weeks. There are no reliable tests that identify latently infected queens or predict which of them will infect their kittens.

When cat flu is dangerous: young kittens, pneumonia and virulent systemic calicivirus

Cat flu turns dangerous in three recognised situations, and an owner who knows all three in advance loses much less time. The three are very young kittens infected before weaning, pneumonia in a cat whose immune system is already compromised, and the rare virulent systemic form of calicivirus.

Kittens before weaning. Infection typically appears between four and eight weeks of age as maternally derived antibody wanes, the source is often the queen whose latent infection reactivated during kittening and lactation, the disease in such young kittens is often severe and involves the entire litter, the level of mortality can be high, and some kittens that recover are left with complications, notably chronic rhinitis. This is the single commonest reason a street-rescued Indian kitten arrives already snuffling.

Pneumonia, especially with a retrovirus underneath. A Brazilian necropsy study assessed 60 cats that died of respiratory disease and found herpesvirus in 12, calicivirus in 7 and both viruses in 3, giving 22 positive cats, of whom 18 had pneumonia. Fourteen of those 22 were co-infected with a retrovirus, six with feline leukaemia virus, four with feline immunodeficiency virus and four with both.

That finding is echoed in living cats. In 120 cats with upper respiratory signs in southern Brazil, retroviral infections were found to increase susceptibility to upper respiratory disease agents, particularly Chlamydia felis and calicivirus. A cat with cat flu that keeps relapsing, or that gets unusually sick from it, is a cat worth testing for FeLV and FIV, because retroviral status changes the whole picture for a chronic snuffler.

Virulent systemic feline calicivirus, and why it is almost certainly not what your sneezing cat has

Virulent systemic feline calicivirus is a rare, outbreak-associated form that behaves nothing like ordinary cat flu. Outbreaks have been described in the United States, China, France, Germany, Austria, Italy, Switzerland, the United Kingdom, Ireland and Korea. The strains cause severe systemic inflammatory response syndrome, disseminated intravascular coagulation, multi-organ failure and usually death, with cutaneous oedema mainly on the head and limbs and crusted ulcers on the nose, lips, ears and around the paws.

The mortality figures are what make it frightening and also what make it identifiable. Mortality is high at roughly 30 to 70 percent, and in two outbreaks over six months in Korea 72 percent of cats (13 of 18) died or were euthanised, while in one French outbreak the figure was 79 percent (11 of 14). Unusually, the disease appears to be more severe in adults than in kittens, which inverts the normal pattern for this virus.

Three things separate it from a runny nose. It spreads as an epizootic through a multi-cat environment rather than appearing in one animal, it produces swelling and skin ulceration rather than sneezing alone, and it kills quickly. There are no diagnostic assays that specifically detect it, so diagnosis relies on the clinical picture, the multi-cat setting, the high contagiousness, the high mortality and isolating the same strain from several diseased cats.

The long tail: chronic rhinosinusitis, the scarred eye and the mouth that never settles

Chronic rhinosinusitis is the outcome most cat flu pages skip, and it is why a cat can sneeze for years after one illness as a kitten. Damage to the nasal turbinates during acute disease is thought to be a predisposing factor for chronic rhinitis, and once that architecture is gone it does not grow back.

The mechanism is worth understanding because it explains why antivirals disappoint here. Chronic rhinosinusitis, a frequent cause of sneezing and nasal discharge, has been associated with herpesvirus infection, but viral DNA is detected only in some affected cats and also in healthy controls, viral replication is not observed, and the likely picture is that the virus initiates the condition which is then maintained by immune-mediated mechanisms, with inflammation and remodelling leading to permanent destruction of nasal turbinates and bone, complicated by secondary bacterial infection. The virus lights the fire and then leaves.

That is also why the honest answer to whether the chronic form can be cured is no, and ABCD's own framing supports it, because the chronic outcomes it lists under herpesvirus are immune-mediated disease rather than active infection, and an exclusion of concurrent infection with other agents is required before a chronic rhinitis is even attributed to herpesvirus.

Working a chronic case up properly is expensive and it is diagnostic rather than therapeutic. In cases of chronic rhinitis and obstructive respiratory syndrome, imaging is needed to separate inflammatory from neoplastic disease, comprising radiography and computed tomography of the head followed by nasal endoscopy, all performed under general anaesthesia. An Indian owner can price that from a government rate card rather than guessing.

Read those prices as what a government teaching hospital publishes, not as a national average; a private referral centre in a metro will be a multiple of it. Every figure was divided by 84.38 and by 74 and none lands on a round dollar figure, so none of them is a converted foreign price.

The eye that does not go back to normal

Herpesvirus keratitis can leave permanent change. In advanced disease, corneal neovascularisation can accompany a stromal keratitis related to immune-complex deposition, with scarring, and where the stroma degenerates a corneal sequestrum forms. A sequestrum is a dark plaque of dead corneal tissue, and it is surgical rather than medical.

Two breeds carry that risk visibly. In 110 Sphynx cats examined at one ophthalmology referral centre over nine years, 42 had corneal sequestrum and 19 had presumed herpetic keratoconjunctivitis, with sequestrum running at 8.0 times the odds of non-Sphynx cats (95 percent confidence interval 5.3 to 12.2) and diagnosed at a significantly younger age. In a French referral population, ulcerative keratitis affected 36 percent of brachycephalic cats (72 of 202) against 15 percent of non-brachycephalic cats (218 of 1,418), which is 3.02 times the odds (95 percent confidence interval 2.20 to 4.14).

That brachycephalic group is exactly the set of breeds Indian buyers gravitate to. The study's brachycephalic cats were Persian, British Shorthair, Exotic Shorthair, Bombay, Burmese, Scottish Fold, Himalayan and Exotic Longhair, and Persians supplied 82 of the 128 affected brachycephalic eyes. A flat-faced cat with cat flu has less margin in its eyes than a domestic shorthair with the same virus.

The mouth that never settles

Feline chronic gingivostomatitis is the calicivirus long tail, and it is a diagnosis that gets handed out too freely. ABCD cautions that severe gingivitis in a cat infected with calicivirus does not automatically make it gingivostomatitis, because by definition the inflammation must extend beyond the mucogingival junction to involve the alveolar mucosa and other soft tissues, and inflammation confined to the gums is not the condition.

The association with the virus is real and strong. In 184 Thai cats, detection of calicivirus on its own carried an odds ratio of 7.15 for gingivostomatitis lesions (95 percent confidence interval 1.89 to 26.99, p equals 0.004). In a free-roaming population screened during trap-neuter-return in South Korea, feline chronic gingivostomatitis was diagnosed in 92 of 345 cats, a prevalence of 26.6 percent.

One thing calicivirus is not responsible for. Calicivirus does not appear to play a role in feline odontoclastic resorptive lesions, which is a separate and very common problem covered on the tooth resorption in cats page.

What is different in India: the word, the tick, the price and the missing evidence

In India, cat flu is a phrase before it is a diagnosis, and three things separate the Indian picture from the British and Australian pages that rank for it. The word points at the wrong disease, the published evidence for the right disease does not exist here, and the vaccine is affordable while the confirmatory test is not on offer.

Start with the word, because it decides what an Indian owner reads first. The Times of India Kolkata report of 21 October 2025 that carries the phrase in its headline is about a tick-borne haemoprotozoan illness, and the veterinarians quoted in it describe checking the head, neck, ears and paws for ticks and removing them with fine-tipped tweezers, with one of them seeing 25 to 30 cases of feline tick fever daily. The disease behind that story has an Indian denominator: Cytauxzoon confirmed in 34 of 90 symptomatic cats screened in Bihar by molecular testing, and in 24 of the same 90 microscopically.

The Indian evidence that does not exist, and exactly how that was checked

There is no Indian clinical series, seroprevalence survey or molecular study of feline herpesvirus or feline calicivirus in the Europe PMC index. That is an absence, so it was tested rather than assumed, with two instruments and a control, on 27 September 2026.

• Title and abstract instrument. A search for feline herpesvirus together with India returned zero records, and the same search for feline calicivirus returned one, which is a wastewater metagenomics paper and not a study of cats.
• Affiliation instrument. Searching feline calicivirus against an Indian author affiliation returned two records, a wastewater surveillance paper and a chemical virus-inactivation study, and the equivalent herpesvirus search returned zero.
• Control, in the same session. The Labrador hip dysplasia control returned 110 on-topic canine papers through the identical route, so the searches ran.
• Positive test on the absence. The Indian feline virology that does exist came back clearly in the same searches, including panleukopenia work from Chennai, Mizoram and Gujarat and the first molecular detection of feline coronavirus from India, so the instrument was finding Indian cat papers and simply found none on these two viruses.

The health roster this page was built from recorded two Indian records for these viruses. Both were artefacts. One is a study of the Delta variant of SARS-CoV-2 in a symptomatic cat in Spain and the other is a wastewater metagenomics paper, and neither describes an Indian cat with cat flu.

The nearest usable data therefore comes from Asian neighbours. In Thailand, samples from 184 cats across several regions between 2016 and 2021 gave detection rates of 46.7 percent for calicivirus, 65.8 percent for herpesvirus and 31.5 percent for co-infection. In Shanghai, 374 urban stray cats gave much lower figures of 3.74 percent for calicivirus and 3.48 percent for herpesvirus, with Mycoplasma felis the dominant finding at 18.72 percent. Those two are not contradictory: the Thai samples came from cats presented to clinics and the Shanghai samples from free-roaming cats caught in the street.

The population this sits in, and why kitten season matters here

India had an estimated 9.1 million stray cats in 2021, and a survey that completed 763 interviews across 13 cities, led by Mumbai at 13.63 percent of responses and taking in Chennai, Lucknow, Kochi, Bengaluru, Ahmedabad, Kolkata, Delhi, Patna, Bhubaneshwar, Nagpur, Varanasi and Vijayawada, found a high rate of sightings and interactions with them; the Animal Welfare Board of India had already issued an advisory to state governments in 2018 about the overpopulation of cats in urban areas. A large share of Indian pet cats begin as street kittens taken in by a neighbour or a rescue, which means they arrive from exactly the density that drives these viruses.

The shelter shedding curve explains what happens next. Four percent of cats are herpesvirus shedders on entering a shelter facility and 50 percent are shedding after one week, which reflects both new infections in naive cats and reactivation in latently infected ones. A kitten that looked well in the box on day one and is sneezing by day eight has followed the published curve exactly, and did not catch it from your house.

What it costs here, and what you cannot buy

The vaccine is the cheap part. The Madras Veterinary College teaching hospital in Chennai, the clinical arm of Tamil Nadu Veterinary and Animal Sciences University, publishes the trivalent CRP that carries both the herpesvirus and calicivirus fractions at Rs 580, with anti-rabies at Rs 160 and small animal registration, valid for seven days, at Rs 100. A private chain prices the three-visit kitten course from Rs 3,999 and the adult annual CRP and anti-rabies visit from Rs 1,899, printed on its own page in the rupee glyph as ₹3,999 and ₹1,899. Every rupee figure on this page was divided by 84.38 and by 74, and none resolves to a round dollar, so none of them is a converted foreign price list.

What you largely cannot buy is confirmation. No Indian government rate card opened for this page lists a herpesvirus or calicivirus PCR, while the Bihar Veterinary College list prices a feline Cytauxzoon PCR at Rs 1,000 and a Theileria, Babesia and Anaplasma panel at Rs 750. The Indian testing market has followed the Indian disease burden, and the tick-borne diseases are where it went.

The last Indian difference is what gets sold instead. The 2015 systematic review recommending an immediate stop to lysine supplementation has not reached the Indian retail listings, one of which still advertises lysine for its known efficacy against herpesvirus respiratory infections in cats. For the schedule, the Indian products and the full price comparison, the cat vaccination schedule in India guide carries the detail this page does not repeat.

Nursing a cat with cat flu at home in India, and the point where that stops being enough

To nurse a cat with cat flu at home, the job is to keep it eating, keep its airways clear, keep it warm and keep it away from other cats, while a veterinarian decides whether anything more is needed. Home care is the treatment for a mild case and it is dangerous as a substitute for a clinic in a severe one.

The steps below are the ones the published advice agrees on, and they are ordered by how much difference each makes.

• Restore the appetite first. Warm the food so it smells stronger, offer strong-smelling wet food, and hand-feed if that is what it takes, because a cat that cannot smell will not eat.
• Keep fluids going. Encourage drinking, since water helps loosen catarrhal secretions, and use steam if the cat tolerates it.
• Clear the face gently. Wipe eye and nasal discharge away with cotton wool and warm water rather than letting it crust over.
• Isolate properly. Give the sick cat its own room with its own litter tray, bed, food and water, away from uninfected cats.
• Disinfect with the right product. Calicivirus resists many disinfectants, so disinfect bowls, trays, bedding and the carrier with something based on sodium hypochlorite, potassium peroxy-monosulphate or chlorine dioxide, which are the three ABCD names.
• Wash hands and change clothes between cats. The virus is carried on clothing, food bowls and other objects.

Two of those steps are harder in an Indian flat than the British pages assume. Isolation in a one-bedroom apartment usually means a bathroom or a balcony, and a balcony in summer is not a sickroom for a cat that is already dehydrated. If the only isolation space available is hot, the cleaner answer is a corner of an air-conditioned room with separate bowls and a separate tray rather than a separate room that cooks.

Monsoon adds the second problem. Damp is exactly the condition calicivirus prefers, because the virus persists longer in damp environments than in dry ones, so a monsoon flat with washing drying indoors is a better environment for the virus than a dry one. Wiping down bowls, trays and the carrier with one of the named disinfectants matters more in July than in January.

Steam is the one home measure that is both cheap and genuinely useful, and it needs no equipment. A cat carried into a bathroom after a hot shower has run gets the same humidified air that a nebuliser would give it, without anyone buying anything.

One last thing worth saying to an owner nursing a first case. Most cats recover from cat flu within weeks, and the most common lasting consequence is not disability but carriage: the cat becomes a carrier of the virus, usually with no way to tell, which means it can be infectious to other cats and may have minor recurrences during stressful times. Planning for that, rather than being surprised by it in two years, is most of what this page is for.