Cat Upper Respiratory Infections: Testing for Feline Herpesvirus, Calicivirus & Panleukopenia at Home

Feline herpesvirus (FHV-1), feline calicivirus (FCV), and feline panleukopenia virus (FPV) are among the most common and dangerous infections in domestic cats. Together, herpesvirus and calicivirus cause the majority of feline upper respiratory tract infections (cat flu), while panleukopenia can be rapidly fatal. At-home rapid tests help identify these diseases quickly so treatment can begin as soon as possible.

Feline Upper Respiratory Tract Infections: An Overview

Feline upper respiratory disease – commonly called “cat flu” – is not a single disease but a syndrome caused primarily by two viruses:

• Feline Herpesvirus Type 1 (FHV-1): Responsible for approximately 50% of cat flu cases
• Feline Calicivirus (FCV): Responsible for approximately 40% of cat flu cases

Both are extremely contagious, spreading through direct contact with infected discharge from the eyes, nose, or mouth. Shared food bowls, bedding, and grooming are common transmission routes. Shelter cats, kittens, and cats living in multi-cat households are at highest risk.

While vaccination provides good protection, it does not always prevent infection – particularly in highly stressed cats or those exposed to large viral loads. Vaccinated cats can still become infected but typically show milder symptoms.

Feline Herpesvirus (FHV-1): Lifelong Latency

Unlike calicivirus, feline herpesvirus establishes lifelong latency in infected cats. Once a cat is infected, it carries the virus for life in nerve ganglia. The virus can reactivate during periods of stress – such as moving house, a new cat, or veterinary visits – causing repeated episodes of clinical disease.

Symptoms of feline herpesvirus infection include:

• Sneezing and nasal discharge (initially clear, progressing to yellow-green)
• Conjunctivitis (red, inflamed eyes with discharge)
• Corneal ulcers (a specific and serious complication of FHV-1)
• Fever, lethargy, and reduced appetite
• Mouth ulcers (less common than with calicivirus)

The Feline Herpes Virus Antigen Test detects the virus directly from an eye, nasal, or oral swab. Early identification allows your vet to prescribe antiviral medications (such as famciclovir) and appropriate supportive care.

Feline Calicivirus (FCV): Oral Ulcers and More

Feline calicivirus is a highly variable virus with many strains. Classic FCV causes respiratory disease similar to herpesvirus, but with some distinguishing features:

• Mouth ulcers (on the tongue, hard palate, or lips) – a classic sign of FCV
• Sneezing and nasal discharge
• Conjunctivitis (milder than with FHV-1)
• Limping syndrome (transient lameness, particularly in kittens)
• Virulent systemic FCV (VS-FCV): a rare but severe form causing facial oedema, skin ulceration, and high mortality

FCV is also notable for its ability to persist in the environment for up to a month on surfaces, making decontamination important in multi-cat environments. The Feline Calicivirus Antigen Test helps distinguish FCV from FHV-1, which guides treatment choices (FCV does not respond to antiviral medications available for herpesvirus).

Feline Panleukopenia: Cat Parvovirus

Feline panleukopenia virus (FPV) – also called feline parvovirus or feline distemper – is one of the most serious and potentially fatal cat diseases. It is related to canine parvovirus and attacks rapidly dividing cells, particularly:

• Cells of the intestinal lining (causing severe vomiting and bloody diarrhoea)
• Bone marrow cells (causing panleukopenia – a dramatic drop in all white blood cells)
• The developing brain in foetuses and newborn kittens (causing cerebellar hypoplasia)

Panleukopenia has a high mortality rate, particularly in kittens and unvaccinated cats. Symptoms develop 2-10 days after exposure and include sudden lethargy and anorexia, profuse vomiting, bloody or watery diarrhoea, severe dehydration, and collapse. The virus survives in the environment for up to one year.

The Feline Panleukopenia Virus Antigen Test provides rapid detection of FPV in faecal samples. Because panleukopenia can progress to death within days, rapid testing is critical. There is also a combination panleukopenia + coronavirus test for simultaneous screening of both pathogens.

Comparing the Feline Rapid Tests

Prevention: Vaccination is the Foundation

Vaccination against FHV-1, FCV, and FPV is included in the core vaccine protocol for cats in virtually every country. These are among the most important vaccines a cat can receive. However, vaccination does not always prevent infection entirely – it greatly reduces severity and duration of illness.

Additional prevention measures:

• Isolate new cats from resident cats for at least 2 weeks before introduction
• Clean shared areas and food bowls with dilute bleach (effective against FPV and FCV)
• Minimise stress, which triggers FHV-1 reactivation
• Test any cat showing symptoms before introducing it to a group

FAQ

Can cat flu spread to humans?

No. Feline herpesvirus, calicivirus, and panleukopenia are species-specific and do not infect humans. However, you can carry the virus on your hands or clothing and transmit it to other cats.

My cat has been vaccinated – can it still get cat flu?

Yes, vaccination significantly reduces severity but does not always prevent infection. Many FCV strains are not fully covered by existing vaccines, and FHV-1 persists as a latent infection throughout a cat’s life. Vaccinated cats typically recover faster and show milder symptoms.

How do I know if my cat has herpesvirus or calicivirus?

Clinically they can be difficult to distinguish. Corneal ulcers strongly suggest FHV-1. Mouth ulcers (especially on the tongue) and limping are more characteristic of FCV. The FHV-1 antigen test and FCV antigen test can confirm which virus is present.

Is panleukopenia (FPV) the same as parvovirus in dogs?

They are related viruses in the same family (Parvoviridae), and canine parvovirus can infect cats (but not vice versa). They cause similar diseases – attacking the gut and bone marrow – but are generally species-specific. The rapid progression of panleukopenia is similar to parvovirus in dogs.

How long does it take to get results from at-home cat tests?

Rapid antigen tests typically give results within 5-10 minutes. Always follow the specific instructions provided with each test.

My kitten is very sick with diarrhoea – should I test at home or go straight to the vet?

If a kitten is very sick, lethargic, vomiting, and has bloody diarrhoea, go to your vet immediately – panleukopenia can be fatal within days. You can run the FPV rapid test en route or ask your vet to test, but do not delay veterinary care for a severely ill kitten.

Be prepared for your cat’s health needs. View all feline diagnostic tests at The Tester.