Feline Herpesvirus (FHV-1) Infection

Overview

A highly contagious virus and, alongside Calicivirus, one of the two primary causes of feline upper respiratory infection — notable specifically for its ability to establish lifelong latent infection, meaning the virus remains dormant in the body indefinitely after the initial infection and can reactivate later, particularly during periods of stress, sometimes causing recurrent respiratory or eye symptoms years after the original infection.

Symptoms

• Sneezing (moderate, very common)
• Eye discharge/conjunctivitis (moderate, very common)
• Nasal discharge (moderate, common)
• Fever (mild, common)
• Corneal ulceration (some episodes) (moderate, uncommon)

Causes

Infection with Feline Herpesvirus-1, transmitted through direct contact with infected cats, respiratory secretions, and contaminated objects.

Risk Factors

Multi-cat environments, lack of vaccination, young age (kittens particularly vulnerable), and stress — which is specifically and notably relevant for this virus given its tendency to reactivate from latency during stressful periods.

Transmission

Highly contagious via direct contact, respiratory secretions, and contaminated surfaces; the virus doesn't survive as long outside the body as calicivirus, making direct or close contact the more significant transmission route. FHV-1 spreads through direct contact with infected secretions, and notably establishes lifelong latent infection in a majority of exposed cats — the virus essentially hides in nerve tissue and can reactivate periodically, particularly during stress, meaning a cat exposed once may experience recurring flare-ups throughout life even without new exposure.

Incubation Period

Typically 2-6 days from exposure to onset of signs.

Disease Stages & Progression

Initial infection typically causes upper respiratory and sometimes eye symptoms, resolving over 1-3 weeks in most cases; critically, the virus then establishes lifelong latency in nerve tissue, capable of reactivating — sometimes repeatedly over a cat's lifetime — particularly during stress, causing recurrent symptoms that can affect the respiratory tract or specifically the eyes (see the Feline Corneal Ulcer entry for herpesvirus's role there). Primary infection typically causes the classic upper respiratory signs (sneezing, nasal/eye discharge, sometimes fever) lasting 1-3 weeks; after apparent recovery, the virus becomes dormant, and stress-triggered reactivation later in life can cause milder recurrent symptoms, most commonly conjunctivitis, without necessarily involving a full new respiratory infection.

Early Warning Signs

Sneezing, nasal discharge, eye discharge/conjunctivitis, and sometimes fever and reduced appetite during an active episode.

Advanced Symptoms

More severe respiratory signs, corneal ulceration (sometimes with a characteristic branching pattern), pneumonia in severe cases (particularly in young kittens), and chronic nasal/sinus issues in some cats with repeated reactivation episodes over time.

Diagnostic Methods

Often diagnosed based on characteristic clinical signs; PCR testing on an eye or respiratory swab can confirm the specific virus when needed, particularly for recurrent or eye-focused presentations where confirming herpesvirus specifically guides treatment (including antiviral eye medication).

Veterinary Examination Process

Assessment of respiratory signs, examination of the eyes for discharge or corneal involvement (using fluorescein staining if a corneal ulcer is suspected), and overall evaluation of hydration and appetite.

Recommended Lab Tests

PCR testing for specific confirmation when needed; general bloodwork for more severely affected cats.

Diagnostic Imaging

Not typically needed for standard cases; chest X-rays if pneumonia is suspected.

Blood Test Indicators

Not specific for routine diagnosis.

Biopsy / Histopathology

Not typically needed for standard diagnosis.

Differential Diagnoses

Feline Calicivirus infection (often co-occurring or presenting similarly), Feline Chlamydiosis, and Feline Bordetellosis.

Home Monitoring Guidance

Supportive home care for mild upper respiratory episodes (keeping the face/nose clean, encouraging eating with palatable warmed food, a warm comfortable environment) is reasonable under veterinary guidance; any eye involvement specifically warrants a veterinary visit rather than home management alone given the risk to the eye if a corneal ulcer is present.

Veterinary Treatment Options

Supportive care addresses standard respiratory episodes; antiviral treatment (oral or topical, particularly for eye involvement) may be used for more significant or recurrent cases. Managing stress can help reduce reactivation frequency in cats with a pattern of recurrent episodes. Supportive care manages acute episodes; L-lysine supplementation was historically commonly recommended, though more recent research has genuinely called its effectiveness into question, making it a less consistently recommended intervention than it once was. Antiviral medication (oral or as eye drops for ocular involvement specifically) is used for more severe or refractory cases.

Surgery Requirements

Not typically needed for standard infection; surgical intervention for a severe, non-healing corneal ulcer would be addressed under that condition's own management.

Recovery Timeline

Initial episodes typically resolve within 1-3 weeks with supportive care; because the virus establishes lifelong latency, there's no 'cure' that eliminates the virus from the body entirely — management focuses on treating active episodes and reducing reactivation triggers.

Possible Complications

Recurrent reactivation episodes throughout life, chronic nasal/sinus changes with repeated episodes over time, corneal ulceration and potential vision impact, and pneumonia in severe cases, particularly in young kittens.

Long-Term Management

Stress reduction (a stable environment, minimizing major changes where possible, addressing any sources of anxiety) is a genuinely relevant long-term strategy given the virus's stress-triggered reactivation pattern; some cats with frequent reactivation may benefit from more targeted, ongoing veterinary management.

Prevention

Core FVRCP vaccination (which includes herpesvirus protection) significantly reduces disease severity, though — similar to calicivirus — may not prevent infection entirely, particularly given how extremely common and easily transmitted this virus is; reducing stress in already-infected cats helps limit reactivation frequency.

Vaccination Availability

Included in the core FVRCP vaccine, widely available and part of standard core vaccination recommendations.

Prognosis

Good for standard episodes with appropriate supportive care; the lifelong latent infection means an excellent short-term prognosis for any given episode doesn't mean the condition is fully 'cured,' which is worth understanding for long-term expectations.

References

American Association of Feline Practitioners (AAFP); American Association of Shelter Veterinarians.

Medications Used

• Antiviral medication (oral or topical, particularly for corneal involvement)
• Antibiotics if secondary bacterial infection develops
• Appetite stimulants if needed
• Lysine supplementation has historically been used, though current evidence for its effectiveness is genuinely mixed and it's no longer as strongly recommended as it once was

Estimated Treatment Cost by Country

Frequently Asked Questions