Eye signs, flares, and how to care for a cat with Feline Herpesvirus.
Feline Herpesvirus (FHV-1) is one of the most common viral infections in cats and the main cause of what owners call cat flu. Most cats live full, comfortable lives with it, but the virus stays in the body for life and can flare during stress. This guide helps you recognise the signs, understand what treatment can and cannot do, care for your cat at home, and know what recovery realistically looks like.
Four parts, from the first signs to living well with it.
Everything you need to manage Feline Herpesvirus (FHV-1) confidently, including the parts that are permanent.
- 1
Recognise the signs
The eye, respiratory and recurrent signs of Feline Herpesvirus (FHV-1).
- 2
Why the eyes matter
The hallmark of Feline Herpesvirus (FHV-1), and why eye signs are urgent.
- 3
Treatment and home care
What HerpX does, what it cannot do, and what you can do at home.
- 4
Recovery expectations
What recovery actually means when a virus stays for life.
What is Feline Herpesvirus in cats?
Feline Herpesvirus (FHV-1) is a highly contagious virus and the primary cause of feline viral rhinotracheitis, part of the upper respiratory disease complex in cats. Its defining feature is latency. After the first infection the virus retreats into the nerves and stays there permanently. It cannot be cleared from the body, but in most cats it stays quiet and only reactivates during periods of stress. This is why treatment focuses on controlling flares and protecting the eyes, rather than on eliminating the virus.
- 1
A virus that stays for life
Once a cat is infected, Feline Herpesvirus (FHV-1) lives in the nerves permanently. Most of the time it stays dormant and causes no signs at all.
- 2
Flares triggered by stress
A house move, a new pet, boarding or another illness can wake the virus. Flares bring sneezing and eye signs, then settle again with prompt care.
Good to know: Feline Herpesvirus (FHV-1) is not the same virus as the human cold sore herpes virus. It infects cats and does not spread to people or dogs.
Recognising signs of Feline Herpesvirus
The picture varies with the cat's age, stress level, and whether other infections are present. Eye signs are the most telling. Watch for these.
- 1Sneezing, often in bouts
- 2Watery or runny eyes
- 3Clear nasal discharge
- 4Squinting or a partly closed eye
- 5Red, swollen conjunctiva
- 6Thick eye discharge
- 7Corneal ulcers
- 8Mild lethargy
- 9Reduced appetite
- 10Repeated eye or respiratory flares
The branching, dendritic corneal ulcer is characteristic of Feline Herpesvirus (FHV-1). Repeated or long lasting eye infections are a classic pattern of the virus reactivating.
Why the eyes matter most
For many cats, Feline Herpesvirus (FHV-1) shows up first and worst in the eyes. The virus attacks the surface of the eye and can cause painful corneal ulcers. Left untreated, severe ocular Feline Herpesvirus (FHV-1) can threaten the eye itself.
Treat eye signs as urgent
If your cat is squinting, holding an eye closed, or has a cloudy spot on the surface of the eye, contact your veterinarian promptly. Eye flares are the situations where prompt antiviral and supportive care make the biggest difference to the outcome.
Treatment and home care
No treatment removes Feline Herpesvirus (FHV-1) from the body, so the goal is to shorten flares, ease the signs and protect the eyes. Home care does not replace veterinary treatment, but it makes a real difference to your cat's comfort during a flare.
HerpX for Feline Herpesvirus.
HerpX is an oral antiviral for Feline Herpesvirus (FHV-1) containing famciclovir, a prodrug of penciclovir and the antiviral most established for the virus in cats. It is used to bring active flares under control, particularly when the eyes are involved.
- Oral antiviral therapy to shorten and control active flares.
- Supportive care alongside it: lubricating eye drops, fluids and nutritional support.
- Antibiotics only where a secondary bacterial infection is present, since the virus itself is not bacterial.
- Dose is set by your veterinarian, based on your cat's weight and how the flare is responding.
- 1
Reduce stress
Stress is the single biggest trigger for flares. Keep routines steady, minimise upheaval, and give a multi cat home enough space, litter trays and hiding spots.
- 2
Keep the face clean
Gently wipe away eye and nasal discharge with a clean, damp cloth, using a fresh area of the cloth for each eye.
- 3
Open the airways
A few minutes in a steamy bathroom, or a humidifier in the room, helps loosen nasal congestion so your cat can breathe and smell food.
- 4
Protect appetite
A blocked nose dulls the sense of smell, so cats stop eating. Warm the food, offer strong smelling wet food, and watch intake. A cat that stops eating needs to be seen quickly.
Never give human cold sore creams or human antiviral tablets on your own. Acyclovir and valacyclovir, both common human antivirals, are associated with toxicity in cats. Famciclovir is the one regarded as systemically safe in cats when dosed appropriately, which is why it is the active ingredient in HerpX. Only give medication your veterinarian has prescribed.
Recovery expectations
With Feline Herpesvirus (FHV-1), recovery means a comfortable cat with controlled signs and protected eyes. It does not mean a virus free cat. Here is what to expect.
- 1
Flares improve quickly
Most flares improve within days to a couple of weeks with prompt, appropriate care.
- 2
The virus does not leave
Even after a full recovery, your cat carries Feline Herpesvirus (FHV-1) for life and may have occasional flares, usually around stressful events.
- 3
Some cats are carriers
Certain cats look healthy but can shed the virus and infect other cats during a flare, so hygiene during flares matters.
- 4
A few need ongoing care
A minority develop chronic signs, such as long term snuffles or recurrent eye problems, and need an ongoing management plan with their veterinarian.
Common questions about Feline Herpesvirus
Can Feline Herpesvirus be removed from the body?+
No. The virus stays latent in the nerves for life, so no treatment clears it. Flares can be controlled well, and most cats live normal, comfortable lives with good management.
Is Feline Herpesvirus contagious to other cats?+
Yes. It spreads easily between cats through direct contact, sneezing, and shared bowls or bedding, especially in multi cat homes and shelters.
Can my cat infect me or my dog?+
No. Feline Herpesvirus (FHV-1) infects cats. It is not the same virus as the human cold sore herpes virus and does not spread to people or dogs.
Can vaccinated cats still get Feline Herpesvirus?+
Yes. Vaccination reduces the severity of disease but does not fully prevent infection or carrier status. It is still strongly recommended.
Does L-lysine help?+
L-lysine is widely sold for Feline Herpesvirus (FHV-1), but the published evidence is mixed and several studies found no clear benefit. Discuss it with your veterinarian rather than relying on it as a main treatment.
Why does my cat keep getting eye infections?+
Recurrent eye infections are a classic pattern, driven by the latent virus reactivating during stress. A plan focused on reducing stress and treating flares promptly helps most.
How long does a flare take to settle?+
Most flares ease within days to a couple of weeks with prompt, appropriate care. Some cats keep shedding the virus for longer, even after the visible signs have cleared.
More questions are answered in the CureFIP FAQ.
Think your cat may have Feline Herpesvirus?
If your cat is sneezing in bouts, squinting, or has watery or crusted eyes, act early, when treatment helps most. Browse HerpX to get started.
This page is for general educational purposes and does not replace veterinary advice. Always consult a qualified veterinarian for diagnosis and a treatment plan tailored to your cat.