When to see a vet urgently
Seek immediate assessment if your cat has:
- open-mouth breathing, marked breathing effort or rapidly worsening breathing difficulty
- an eye held closed, strong squinting or corneal cloudiness
- failure to eat or drink together with clear lethargy
- rapid deterioration or signs of dehydration in a kitten
You can find a vet near you. Do not monitor breathing difficulty or a painful eye as ordinary cat flu.
Epidemiology and distribution
Herpesvirus is very common: as many as 80–90% of cats have been exposed during their lifetime. Infection risk is greatest in:
- kittens under one year old
- shelters and breeding catteries
- unvaccinated cats
- cats with chronic diseases or weak immune systems
The 80–90% estimate does not describe every cat population equally. The proportion exposed, the proportion with lifelong latent infection and the proportion shedding virus at sampling are different things. Test methods and living conditions affect figures, so the percentage cannot establish an individual cat's infectiousness.
After recovery, a cat remains a carrier and may shed virus particularly during stress.
Disease course and features
FHV-1 infects the nasal, throat and eye mucous membranes. It multiplies in epithelial cells, causing inflammation and tissue damage. Symptoms are clear during the acute stage, but afterwards the virus remains hidden in nerve cells. Stress or other diseases can reactivate it.
Latency means a hidden phase in which the virus persists in nerve cells. It does not mean a continuously active runny nose or uninterrupted shedding. Reactivation can cause symptoms, but can also occur without illness that you notice.
Cat flu is an umbrella term involving several pathogens. Calicivirus, Chlamydia and Mycoplasma can cause partly similar respiratory and eye signs, and concurrent infections occur. Finding FHV-1 therefore does not rule out other factors contributing to symptoms.
Symptoms in cats
In adult cats:
- sneezing and coughing
- clear or pus-like nasal and eye discharge
- conjunctivitis and squinting
- reduced appetite and lethargy
- fever
In kittens:
- severe eye damage, including corneal ulcers and keratitis
- heavy discharge that interferes with breathing
- loss of appetite due to reduced smell
- delayed growth
- high mortality without treatment
Chronic form:
- persistent watery eyes and nasal discharge
- chronic rhinitis
- recurring symptoms during stress
- progressive eye damage and impaired vision
This list does not mean every kitten or chronic carrier develops severe disease. Severe respiratory signs are less common in appropriately vaccinated adult cats. A kitten's prognosis also depends on maternal antibodies, general condition and food and fluid intake.
The cornea is the clear front surface of the eye. An ulcer can cause pain, keeping the eye closed and avoiding light. A small amount of visible discharge does not indicate ulcer depth. Persistent eye signs need examination even if herpesvirus has previously been diagnosed.
Persistent coughing or difficult breathing alone does not identify FHV-1. An ill cat may also need assessment of the lungs and other respiratory diseases. Clearly increased breathing effort particularly requires urgent assessment rather than ordinary home care for a blocked nose.
Consequences
FHV-1 can cause serious complications:
- chronic rhinitis and breathing difficulties
- corneal ulcers and blindness
- bacterial infections
- death in kittens due to dehydration and weakness
Complications are possible, but carrier status does not mean inevitable progressive eye damage or poor quality of life. Many cats live normal lives despite occasional episodes. A scarred cornea or persistent nasal signs may still need monitoring after acute infection settles.
Diagnosis at the vet
Your vet may use the following methods:
- clinical examination and medical history
- PCR testing of nasal or eye samples
- eye examination with an ophthalmoscope
- additional tests to exclude other diseases, such as calicivirus or chlamydial infection
Interpreting PCR results
PCR looks for viral genetic material in the sample. A positive result may reflect active disease, but also low-level shedding without symptoms. It does not, on its own, show that herpesvirus causes all current signs. The finding is compared with examination of the eyes and respiratory tract.
A negative sample does not reliably rule out latent infection either. Shedding is intermittent, and sample site and quality affect results. The test therefore cannot serve as a simple certificate that a new cat could never infect others.
Examining the eyes
The eye's surface is examined using fluorescein dye to reveal damaged areas. Tear production is measured where necessary. Looking at the back of the eye alone does not replace examination of the cornea and conjunctiva, as key FHV-1 changes may occur in those structures.
Repeat staining can confirm ulcer healing. Pain easing or discharge decreasing does not, by itself, prove the surface has healed completely. Sampling and eye examination order are planned at the clinic if pathogen testing is also needed.
Treatment
Treatment depends on symptoms and general condition. Mild disease requires adequate eating and drinking and gentle removal of discharge. A severely ill, dehydrated or non-eating cat may need hospital care, fluids and nutritional support. Breathing difficulty may also require supplemental oxygen.
Antivirals may be used particularly for eye signs and severe herpes infections. They do not permanently remove latent virus from nerve cells. An antibiotic instead targets any bacterial infection, rather than herpesvirus itself. Medication needs depend on findings, and not every episode of nasal signs receives the same prescription.
Do not use drops left from a previous eye disease without new instructions. Corticosteroid-containing medicine in particular can delay healing or cause serious problems in an ulcerated cornea. Your vet assesses the ulcer and inflammation before choosing medication and arranging the necessary follow-up.
Lysine has been used as support for herpes infection, but research does not demonstrate reliable benefit for prevention or treatment. Do not use it or other supplements marketed as immune support to replace nutrition, eye care or prescribed antiviral treatment.
Home care and monitoring episodes
Gently wipe discharge from around the eyes and nostrils with a clean, damp cloth. Use a different clean section for each eye. A blocked nose can reduce appetite through impaired smell; aromatic, palatable wet food may help. If intake remains inadequate, contact your vet.
Record appetite, alertness, breathing and eye changes. Tell the clinic about difficulty giving medication because repeated strong resistance increases stress. The approach may need adapting to suit your cat better. New eye pain is not automatically interpreted as a harmless recurrence of an old infection.
Transmission
- Direct contact with ill cats.
- Droplets from coughing or sneezing.
- Shared food bowls and toys.
- From mother to kittens.
FHV-1 is adapted to cats and does not infect people as human herpes. Some other microbes associated with feline eye or respiratory signs can be zoonotic, however, so hand hygiene is needed. Hands and care equipment can also transfer secretions between cats.
Prevention
Vaccination offers the best protection:
- FHV-1 vaccination is a core vaccination; follow a kitten primary course planned by your vet.
- Agree boosters according to age, previous vaccination, the product and infection risk; vaccination reduces disease severity but does not prevent carrier status.
- Review ongoing booster requirements with your vet.
Booster recommendations form an individual plan rather than additional overlapping instructions for every cat. Intervals depend on the product, previous vaccinations and infection risk. Vaccination particularly reduces severe disease risk but does not guarantee prevention of infection, carrier status or shedding.
Also:
- quarantine new cats for at least 2 weeks
- disinfect toys and food bowls regularly
- minimise stress
- provide a balanced diet and support immune health
- arrange regular veterinary visits
Quarantine duration and implementation are agreed according to circumstances. A symptom-free period alone does not rule out latent FHV-1. Care for an ill cat separately with its own bowls and equipment, paying attention to hand hygiene and removal of secretions during cleaning.
Wash away visible dirt before disinfecting because organic material reduces the effects of many products. Choose one suitable for a cat environment and follow its application and contact time. Do not mix cleaning products. Prevent access to wet treated surfaces according to instructions.
A quiet resting place of its own, hiding opportunities and suitable play help reduce stress. In a multi-cat home, provide enough clean litter trays and other separate resources. Make household changes while monitoring adaptation. These measures support daily life but cannot prevent every recurrence.
Important for cat owners
- A cat remains a virus carrier for life.
- Symptoms can recur during stress.
- Vaccination and good care reduce the risk of symptoms.
- Kittens and older cats need particular protection.
This text provides general information and does not replace veterinary care. Contact a vet if your cat develops symptoms.
Frequently asked questions
Can a vaccinated cat get FHV-1?
Yes. Vaccination reduces disease severity and helps limit harm, but does not prevent every infection or carrier state. A vaccinated cat with symptoms is examined where necessary too.
Does a positive PCR mean every symptom is due to herpesvirus?
Not necessarily. It can also detect shedding without symptoms, and other pathogens or an eye disease may be present in the same cat. Results are interpreted alongside examination findings.
Can feline herpes infect people?
FHV-1 does not infect people; it is a feline virus. Handwashing after handling secretions is still needed because other microbes may be present and infection can transfer to other cats.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- GUIDELINE for Feline Herpesvirus infection, European Advisory Board on Cat Diseases, accessed 2026-11-03.
- Respiratory Infections, Cornell University, accessed 2026-11-03.
- Feline Respiratory Disease Complex, Merck Veterinary Manual, accessed 2026-11-03.
- Herpesvirus Infection in Cats (Feline Viral Rhinotracheitis), VCA, accessed 2026-11-03.
- Corneal Ulcers in Cats, VCA, accessed 2026-11-03.
- GUIDELINE for Disinfectant choice in feline veterinary hospitals, shelters and cat households, European Advisory Board on Cat Diseases, accessed 2026-11-03.
- Basic Indoor Cat Needs, The Ohio State University, accessed 2026-11-03.