CONDITION
Feline Herpesvirus (FHV-1)
Feline herpesvirus type 1 is one of the primary causes of upper respiratory infection in cats, characterised by sneezing, nasal discharge, and eye problems, with most infected cats becoming lifelong carriers.
Why this matters now
Feline herpesvirus infection is extremely common, with most cats exposed during kittenhood, particularly in multi-cat environments or rescue situations. Initial infection typically causes respiratory illness, while subsequent flare-ups can occur throughout life during periods of stress or immune compromise.
Primary infection usually affects kittens, causing sneezing, nasal congestion, and eye inflammation that peaks over one to two weeks. Following recovery, the virus establishes latency in nerve tissue, remaining dormant but periodically reactivating. Stress, other illness, or immunosuppression can trigger recurrence, with signs typically milder than the initial infection but sometimes affecting the eyes significantly.
Signals & patterns
Early signals
Sneezing episodes
Frequent, sometimes violent sneezing is often the first sign of upper respiratory infection.
Watery eye discharge
Clear fluid from one or both eyes, sometimes with reddening of the conjunctiva.
Clear nasal discharge
Runny nose that may later become thicker and discoloured if secondary bacterial infection develops.
Mild fever
Elevated body temperature may accompany acute infection, though often subtle.
Later signals
Thick, coloured nasal discharge
Yellow or green discharge suggests secondary bacterial infection complicating the viral illness.
Mouth breathing
Severe nasal congestion forces cats to breathe through their mouth, affecting eating and comfort.
Corneal ulcers
Herpesvirus can damage the surface of the eye, causing painful ulceration visible as cloudiness or squinting.
Reduced appetite
Inability to smell food due to congestion significantly reduces interest in eating.
Click to read about the biological mechanisms
How this is usually investigated
Diagnosis often relies on clinical signs in conjunction with history, as testing for herpesvirus has limitations in distinguishing current infection from latent carrier status.
Clinical examination
PCR testing
Fluorescein eye stain
Schirmer tear test
Blood tests
Options & trade-offs
Management combines supportive care during active episodes with strategies to reduce recurrence frequency and address specific complications like eye disease.
Supportive nursing care
Steam inhalation, gentle nasal cleaning, and encouraging food intake
Trade-offs: Essential foundation of treatment; requires owner commitment; addresses symptoms while virus runs its course.
Antiviral medication
Drugs like famciclovir that reduce viral replication
Trade-offs: Can shorten episodes and reduce severity; requires veterinary prescription; cost consideration; palatable formulation important.
Topical antiviral eye drops
Medication applied directly to affected eyes for ocular disease
Trade-offs: Targets eye involvement; requires frequent application; can be challenging to administer; often combined with systemic treatment.
L-lysine supplementation
Amino acid historically used to suppress viral replication
Trade-offs: Widely used and safe; recent research questions effectiveness; may still benefit some cats; palatable supplement available.
Antibiotics
Treatment for secondary bacterial infections complicating the viral illness
Trade-offs: Does not treat the virus itself; addresses bacterial component; important for complicated cases.
Stress reduction
Environmental modifications to reduce triggers for reactivation
Trade-offs: Addresses underlying cause of flare-ups; long-term benefit; requires understanding individual stressors.
Common misconceptions
"Cats that recover from herpesvirus are no longer infected"
Most cats become lifelong carriers after initial infection, with the virus remaining dormant in nerve tissue and periodically reactivating.
"Vaccination prevents herpesvirus infection completely"
Vaccination reduces disease severity and shedding but does not prevent infection or eliminate carrier status in previously infected cats.
"Herpesvirus can spread from cats to humans or other species"
Feline herpesvirus is species-specific and poses no risk to humans or other animals; it is unrelated to human herpes viruses.
Cat owners recognising respiratory signs or eye problems in their pet can understand that feline herpesvirus is extremely common and usually manageable. Awareness that stress triggers flare-ups and that supportive care forms the cornerstone of treatment helps frame realistic expectations for living with a carrier cat.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS