How Long Does Cat Flu Hide Before Striking?


Cat flu refers to a range of infections in cats that cause upper respiratory symptoms like runny eyes and nose, sneezing, fever, and lethargy. Cat flu is a common illness in cats While it can cause significant discomfort in cats, it usually resolves on its own. However, kittens and cats with weak immune systems are at higher risk for complications from cat flu.

The most common causes of cat flu are viral infections like feline herpesvirus and calicivirus. These viruses spread easily between cats and infect the upper respiratory tract, leading to inflammation and respiratory signs Bacterial infections can also play a role. Cat flu is not contagious to humans, but it’s important to keep infected cats isolated from other pets. While curable cases are possible, most cats continue to carry the virus latent in their system even after recovery.


The two main causes of cat flu are Feline herpesvirus (FHV-1) and Feline calicivirus (FCV). These viruses account for approximately 90% of upper respiratory infections in cats (source).

Feline herpesvirus is highly contagious and causes fever, nasal discharge, sneezing, coughing, eye discharge, and ulcers on the cornea. The effects of FHV-1 tend to be more severe in kittens. Once a cat is infected with herpesvirus, they are infected for life. The virus goes dormant but can reactivate during periods of stress.

Feline calicivirus also causes similar upper respiratory symptoms including nasal discharge, ulcerations and respiratory issues. This virus mutates frequently, making natural immunity difficult. Most cats recover within 2-4 weeks, however some strains cause more severe disease. Calicivirus is very contagious and transmitted through respiratory secretions and saliva (source).


Cat flu spreads between cats primarily through direct contact. When an infected cat sneezes, coughs, or even just breathes, it releases viral particles that can infect other cats. These particles enter the body through the nose or eyes of uninfected cats. Direct forms of contact that spread cat flu include:

  • Nuzzling or close face-to-face contact
  • Licking and grooming
  • Sharing food bowls
  • Sneezing or coughing directly at another cat

Cat flu can also spread indirectly when viral particles land on surfaces like food bowls, litter boxes, bedding material, and toys. When uninfected cats come in contact with these contaminated objects, they can pick up the virus. Cat flu viruses can survive in the environment for several days or even weeks in optimal conditions. In shelters or multi-cat households, the virus spreads rapidly through the entire population due to close contact and shared items.

Incubation Period

The incubation period refers to the time between exposure to an infectious agent and the appearance of the first clinical signs and symptoms of the disease. For cat flu (feline herpesvirus and calicivirus), the typical incubation period is 2-10 days (Cat Flu – Upper Respiratory Infection).

After initial exposure to the herpesvirus or calicivirus, it takes a few days for the virus to multiply and spread within the cat’s body and reach transmissible levels. Most cats will begin showing symptoms within 2-6 days, though it can take up to 10 days in some cases (Cat flu information sheet). The incubation timeframe can vary slightly depending on the specific viral strain, the cat’s immune response, and other factors.

Knowing the typical incubation period for cat flu is important to monitor cats after potential exposure and isolate sick cats to prevent spreading the infection. Cat owners should watch for symptoms for up to 10 days after suspected contact with infected cats.

Common Early Symptoms During the Incubation Period

Cats with feline upper respiratory infections (also called cat flu) often start showing symptoms within 2 to 10 days after exposure to the virus (Cat Flu | Symptoms, Causes, and Treatment). During the incubation period, some of the earliest signs of cat flu include:

  • Sneezing
  • Watery eyes and nose discharge
  • Loss of appetite
  • Lethargy
  • Congestion
  • Fever

Cats may also develop mouth ulcers and lose their voice as the infection progresses. However, these symptoms usually take a bit longer to appear than the initial upper respiratory signs like sneezing and watery eyes (Feline Upper Respiratory Infection (Cat Flu)). Being aware of the early symptoms can help cat owners recognize feline upper respiratory infections quickly and get veterinary treatment started right away.


Veterinarians diagnose cat flu based on the clinical signs and symptoms. They will take a full medical history and perform a thorough physical exam of the cat. Diagnostic tests that may be performed include:

  • Nasal and ocular discharge samples – Samples are taken with swabs from the nasal cavity and eyes. These samples can be analyzed for the presence of viral organisms like herpesvirus or calicivirus that cause cat flu.
  • Complete blood count (CBC) – A CBC can detect an elevated white blood cell count, indicating infection or inflammation.
  • Chest x-rays – X-rays allow vets to see any abnormalities in the lungs that may indicate pneumonia secondary to cat flu.
  • Additional tests – Vets may recommend blood chemistry, urinalysis, FeLV/FIV testing, and other assessments to rule out underlying issues.

While laboratory tests can confirm cat flu, many vets diagnose based on clinical signs alone since treatment is often the same regardless. Rapid point-of-care tests for respiratory viruses are also becoming more available in veterinary clinics.

According to Blue Cross, diagnosis to identify which type of cat flu they have may be made by taking swabs and looking for the virus but, in most pet cats, this is not usually necessary.


Cat flu is treated with medications prescribed by a veterinarian. Common medications used are antibiotics like doxycycline to fight secondary bacterial infections and anti-inflammatories like meloxicam to reduce fever and make the cat more comfortable (WebMD, 2022). Antibiotics are crucial for treating secondary infections but are not effective against the primary viral infection. There are currently no antiviral medications approved for treating cat flu viruses (Trudell Animal Health, 2022).

In addition to medications, supportive care at home is important for cats recovering from cat flu. Make sure the cat eats and drinks enough by providing palatable food like canned cat food. Help clear nasal congestion by placing the cat in a steamy bathroom. Disinfect food bowls and litter boxes daily and isolate sick cats from other pets (Blue Cross, 2023). With appropriate medication and home care, most cats recover fully in 2-4 weeks.


WebMD. (2022). Cat Flu: Symptoms, Treatment, and Prevention.

Trudell Animal Health. (2022). Feline Upper Respiratory Infection (Cat Flu).

Blue Cross. (2023). Cat Flu | Symptoms, Causes, and Treatment.


There are several ways to try to prevent cat flu infection (

The most effective prevention method is vaccination. Kittens can be vaccinated against cat flu starting as young as 8 weeks old, with a booster shot given 3-4 weeks later. After that, annual vaccination is recommended to maintain immunity ( The vaccine helps prevent infection, though it is not 100% protective if a cat is heavily exposed. Vaccination can reduce the severity of symptoms if a cat does become infected.

To help prevent the spread of infection, isolate any new cats entering the home for a period before introducing them to other household cats. Good hygiene is also important, including washing hands before and after handling cats and keeping food bowls, bedding, and litter boxes clean ( Limiting interactions with outdoor/stray cats can reduce exposure risk.

While cat flu cannot be fully prevented, following these precautions can help reduce the likelihood of cats becoming infected and developing serious illness.


The prognosis for cats with feline calicivirus or herpesvirus infections depends on the severity of symptoms. According to Blue Cross, many cats will recover completely and are no longer contagious after 1-2 years ( With mild cases, cats may recover fully within 5-10 days. More severe cases involving secondary infections can take up to 6 weeks for recovery (

While many cats recover completely, complications can sometimes occur. Secondary bacterial infections are common and may lead to pneumonia. In rare cases, the calicivirus can cause painful ulcerations on the tongue, hard palate, and nose. Some cats may experience chronic nasal discharge or eye symptoms due to permanent damage from the infection ( However, with prompt veterinary treatment, most cats can fully recover from cat flu.


In summary, the incubation period for cat flu, also known as feline viral rhinotracheitis caused by feline herpesvirus, is typically 2-10 days. During this time, the virus multiplies rapidly but the cat will not yet show any symptoms. Most cats will begin to show signs of infection within 2-6 days after exposure. The incubation period can be influenced by factors like the viral load, exposure route, and individual immune response. After the incubation period ends, cats usually start displaying symptoms like sneezing, eye and nasal discharge, fever, lethargy, and loss of appetite. To control the spread of cat flu, newly exposed cats should be quarantined for at least 2 weeks. While antibiotics won’t treat the underlying viral infection, they may help prevent secondary bacterial infections. Supportive care and keeping the cat comfortable are the mainstays of treatment. Most cats recover fully within 2-4 weeks, but the virus remains latent and periodic reactivation is possible throughout their lifetime.

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