Introduction
Flu viruses that normally circulate in people can sometimes infect cats. Cat flu is the common name for the upper respiratory infection caused by these viruses. The most common strains infecting cats are H7N2 and H3N2. Cat flu is very contagious among cats and can cause symptoms like fever, lethargy, sneezing, and discharge from the nose or eyes. While rare, cat flu viruses can sometimes spread to humans. However, the risk is low and they typically do not cause severe illness in healthy people. This article will provide an overview of cat flu, including the causes, transmission, symptoms, diagnosis, treatment, prevention, and zoonotic potential.
What is Feline Influenza?
Feline influenza virus (FIV) refers to strains of influenza A virus that can infect domestic cats. The two main strains are H5N1, an avian influenza virus, and H3N2, which emerged in Asia in the 2000s (Frymus, 2021).
FIV is very similar to human influenza viruses. Both are influenza A viruses that can cause respiratory disease. However, to date, FIV strains are genetically and antigenically distinct from human seasonal influenza A virus strains. This means that human flu vaccines do not protect against FIV and vice versa (CDC, 2022). Additionally, while human-to-human transmission is very efficient, cat-to-cat transmission of FIV appears to be less frequent (Frymus, 2021).
FIV was first discovered in 2004, when an outbreak occurred in tigers and leopards at a Thai zoo. Since then, it has spread globally in the domestic cat population. However, many infected cats show no symptoms. When symptoms do occur, they are similar to human flu including fever, lethargy, appetite loss, and respiratory signs like coughing and sneezing (CDC, 2022).
Transmission
Feline influenza spreads through direct contact between cats. According to the CDC, “The virus is shed in respiratory secretions and can be directly transmitted by sneezing, coughing or breathing.”
The two main risk factors for feline influenza transmission are:
- Direct contact with an infected cat – The virus spreads easily between cats in multi-cat households or shelters through saliva, mucus, sneezing, coughing, etc. Sharing food bowls, water bowls and litter boxes can facilitate transmission.
- Indirect contact with contaminated objects/surfaces – The virus can survive for 24-48 hours on surfaces. Exposure can occur by touching contaminated toys, bedding, food/water bowls, litter boxes, etc. Humans can also carry the virus on clothing after touching an infected cat. (https://www.bluecross.org.uk/advice/cat/health-and-injuries/cat-flu)
Symptoms
The most common signs of feline influenza are similar to the symptoms of the common upper respiratory infections in cats. According to the Blue Cross https://www.bluecross.org.uk/advice/cat/health-and-injuries/cat-flu, the symptoms generally include:
- Sneezing
- Runny nose and eyes
- Fever
- Lethargy
- Loss of appetite
- Coughing
Cats may also develop ulcers in the mouth and nose. In severe cases, pneumonia can develop which leads to labored breathing and difficulty breathing. The severity of symptoms can range from mild to severe. Most cats have a mild illness, but kittens, older cats, and cats with other medical conditions are at higher risk for more severe symptoms.
Diagnosis
There are a few options for diagnosing feline influenza in cats:
Veterinarians can take nasal or throat swabs and test them for the presence of the feline influenza virus. This testing can identify whether a cat is actively infected. Results may come back positive for influenza A or a specific subtype like H3N2 or H3N8. According to the CDC, polymerase chain reaction (PCR) tests are most accurate for diagnosis. https://www.cdc.gov/flu/avianflu/diagnosis-testing.htm
Blood tests can check for antibodies to feline influenza. A positive antibody test indicates a cat was exposed to the virus at some point, but does not necessarily mean an active infection. Paired acute and convalescent blood samples 2-3 weeks apart can show rising antibody levels indicating recent infection.
Veterinarians may also use clinical signs and case history to make a presumptive diagnosis. Common symptoms like fever, lethargy, nasal discharge and sore throat in a cat with potential exposure to infected cats may point to feline influenza. Definitive diagnosis requires laboratory testing.
Positive test results confirm feline influenza infection. However, negative results do not completely rule it out since sampling technique impacts detection. Veterinarians may need to retest or diagnose based on symptoms.
Treatment
Treatment for feline influenza focuses on supportive care to relieve symptoms and promote recovery. According to the Blue Cross, most cats can recover at home with rest, warmth, hydration, and appetizing food [1].
Antiviral medications may be prescribed in severe cases to fight the viral infection. Trudell Animal Health states that antivirals like oseltamivir can shorten the duration and reduce the severity of symptoms [2]. However, antivirals are most effective when started early in the infection.
Antibiotics may also be prescribed if there is a secondary bacterial infection present. WebMD notes that antibiotics can help clear up bacterial infections that often accompany feline influenza [3]. Reducing these secondary infections helps cats recover more quickly.
With supportive care and medication if needed, most cats fully recover from feline influenza within 2-4 weeks.
Prevention
There are a few ways to help prevent feline influenza in cats:
Vaccination is the best way to protect cats from feline influenza. There are vaccines available that protect against the H3N8 and H3N2 strains of the virus. Vaccination helps reduce the severity of symptoms if a cat does become infected. Kittens should receive an initial vaccination series followed by annual boosters (Source 1).
Biosecurity measures can also help prevent the spread of feline influenza. This includes isolating any new cats entering a home or cattery for a minimum of 7-10 days. Litter boxes, food bowls, and other items should not be shared between cats during the isolation period. Any equipment used for infected cats should be thoroughly disinfected before being used by other cats (Source 2). Catteries and shelters should have strict biosecurity protocols to avoid outbreaks.
In addition, limiting a cat’s exposure to stray and feral cats can reduce their risk. Indoor cats have less opportunity to come in contact with the virus. Washing hands after contact with any outside cats can also help stop transmission.
Prognosis
The prognosis for feline influenza is generally good, especially for cats who are otherwise healthy. According to the CDC, the fatality rate for feline influenza is less than 10%[1]. Most cats will recover within 2-4 weeks with supportive care and treatment. However, kittens and cats with underlying illnesses are at higher risk for complications and mortality[2].
Potential complications from feline influenza include secondary bacterial infections such as sinusitis or pneumonia. These can lead to more severe illness and extended recovery times. In rare cases, permanent damage to the lungs or other organ systems can occur[3]. With appropriate veterinary care, most cats will make a full recovery. However, fatality rates are higher in susceptible populations. Prompt treatment is key to preventing complications and reducing morbidity and mortality associated with feline influenza.
Zoonotic Potential
Feline influenza has the potential to spread to humans, although the risk is low. According to the CDC, there have only been a few isolated cases of humans becoming infected with influenza viruses that normally circulate in cats [1]. However, the CDC notes that more research is needed to fully understand the zoonotic threat. Some possible ways humans could contract feline influenza include [2]:
- Direct contact with a sick cat and touching contaminated secretions
- Inhalation of aerosols containing the virus
- Indirect contact by touching contaminated surfaces
The symptoms of feline influenza in humans appear to be similar to typical human seasonal flu. Cases are rare, but immunocompromised individuals may be at higher risk. Overall, while feline influenza has zoonotic potential, the current evidence suggests the risk of transmission from cats to humans is low.
Conclusion
In summary, while the flu virus mainly infects humans, cats can also get sick from influenza viruses. Cats are susceptible to feline influenza viruses H3N2 and H3N8 which are adapted from human and avian flu strains. Feline influenza is highly contagious between cats and the most common way it spreads is through direct contact with respiratory discharges from infected cats. Symptoms are similar to the human flu and include fever, lethargy, appetite loss and respiratory signs like coughing and sneezing. There is no cure for feline influenza but the disease is usually mild and self-limiting. Supportive care helps cats recover. Vaccination is available to protect cats from illness. While human flu viruses rarely infect cats, there is no evidence of cat-to-human transmission. But it’s still important for cat owners to practice good hygiene and minimize their cat’s exposure to unwell humans or other animals. With prompt veterinary care, most cats fully recover from feline influenza.
