Feline Herpesvirus (FHV-1 / Feline Viral Rhinotracheitis)

Overview

Feline Herpesvirus (FHV-1), also called Feline Viral Rhinotracheitis (FVR), is one of the two major viruses behind "cat colds" — the other being calicivirus, covered elsewhere in this library. It's extraordinarily common: an estimated up to 97% of cats are exposed at some point in their lives, and once infected, cats become lifelong carriers.

• Extremely common — most cats have been exposed by adulthood
• Once infected, the virus becomes lifelong and latent (dormant), capable of reactivating during stress
• Not contagious to humans or other species — cat-specific only
• Generally has a good prognosis for recovery from individual flare-ups, though recurrence is common

Common Symptoms

Typical Flare-Up

• Sneezing with nasal discharge
• Conjunctivitis (eye inflammation/discharge) — often more prominent than with calicivirus
• Oral ulcers (less common than with calicivirus, but can occur)
• Corneal ulcers — a distinguishing feature of herpesvirus specifically; raises suspicion especially in both eyes or in young/unvaccinated cats

Severe / Kitten Cases

• Young kittens with poor immune response can develop severe nasal/eye inflammation, sometimes leading to permanent facial or sinus deformity
• Kittens who recover from a severe pediatric infection may have chronic, recurrent nasal/sinus inflammation for life due to that early structural damage

Possible Causes

• Direct contact with an infected cat, or contact with contaminated surfaces/objects
• Reactivation (recrudescence) of a dormant infection is triggered by stress — this includes boarding, moving to a new home, lactation, illness, or other physical stressors
• Studies show reactivation happens in around 70% of latently infected cats following steroid treatment experimentally, and stress-related triggers like moving environments (about 18%) or lactation (about 40%) are recognized real-world triggers

Diagnosis

• Often diagnosed based on clinical pattern: sneezing, nasal/eye discharge, conjunctivitis, and especially corneal ulcers, particularly in young or unvaccinated cats
• No perfect direct test exists for latency itself, since the virus hides silently within nerve tissue between flare-ups
• During an active flare-up, testing (PCR, viral isolation) can confirm active infection if needed

Treatment

• No cure — treatment is symptomatic and supportive during flare-ups
• Antiviral eye drops for corneal ulcers/conjunctivitis; oral antiviral medication (like famciclovir) for more severe or recurrent cases
• Antibiotics only if a secondary bacterial infection is suspected, not for the virus itself
• L-lysine is commonly recommended, though it's worth knowing that while lab studies showed promise, there isn't strong published evidence it helps in cats with natural infection — many vets and owners still use it anecdotally
• Cats prone to recurrence may benefit from periodic booster vaccination (intranasal combo vaccine), which can help reduce reactivation frequency

Nutrition & Food Intake

• Congestion reduces smell-driven appetite; warming food or offering strongly-scented wet food can help
• Adequate hydration matters, especially during active flare-ups
• No specific "herpesvirus diet" exists beyond general supportive nutrition during illness

Home Physical Checks (What to Look For Yourself)

• Eyes – watch for one or both eyes affected, discharge type, and especially any cloudiness or visible ulceration on the eye surface (corneal ulcers need prompt attention to prevent permanent damage)
• Nose – sneezing frequency and discharge character
• Stress triggers – note any recent changes (new pet, move, boarding, illness) that might explain a flare-up in a known carrier cat
• Recurring pattern – tracking how often flare-ups happen and what seems to trigger them can help your vet tailor a management plan

Supportive Supplements (General Info — Not a Prescription)

• L-lysine – widely used, though evidence in naturally-infected cats is limited; discuss with your vet whether it's worth trying for your cat specifically
• Nebulization with sterile saline – used by some vets, especially for cats with chronic nasal/sinus changes from an early severe infection, to help with ongoing symptom relief
• These are supportive measures, not cures — the virus itself remains lifelong regardless

When to Seek Emergency Care

Seek prompt veterinary care if:

• Corneal ulcers are suspected (visible cloudiness, squinting, eye pain) — these need timely treatment to prevent permanent vision damage
• A kitten with severe symptoms stops eating or becomes very lethargic
• Symptoms don't improve after a week or clearly worsen

Prevention

• Vaccination (part of the standard FVRCP combo vaccine) doesn't prevent infection entirely but significantly reduces severity and shedding
• Minimize stress for known carrier cats — consistent routine, reducing overcrowding, gentle transitions during moves or boarding
• Isolate new cats before introducing them to a household or shelter population
• Periodic booster vaccination for high-risk cats (shelter cats, breeding colonies, frequent boarders) may help reduce reactivation frequency

Prognosis

Generally good for individual episodes, with an important caveat about recurrence:

• Most cats exposed to FHV-1 live long, normal lifespans — this is not typically a life-shortening diagnosis on its own
• The virus is not curable; it goes into remission between flare-ups, and most cats appear completely normal in between episodes
• Recurrence is common and can mean repeated treatment episodes over a cat's life, which can add up in cost and management effort, but doesn't usually indicate a worsening underlying condition
• Kittens with severe initial infections are the group most likely to have lasting structural changes (chronic sinus issues) — this is where early, aggressive treatment during the first infection matters most for long-term outcomes

Sources: Cats.com; ABCD Cats & Vets Guidelines; Cat Fanciers' Association; VCA Animal Hospitals; PMC ocular herpesvirus research.