Cat flu, also known as a feline upper respiratory infection, is a condition that can affect cats of all ages and breeds. It's similar in a way to a human's common cold, since it affects the cat's respiratory system. 

While this disease isn’t generally life-threatening in healthy adult cats, it’s still a major concern. Cat flu can be dangerous for kittens, old cats, and cats with weak immune systems.

In this blog, we’ll share everything you need to know about cat flu, from what it is to how it’s treated. 

What Causes Cat Flu?

Cat flu is a term for an upper respiratory infection that is usually caused by two viruses: feline herpesvirus and feline calicivirus. Additionally, cat flu can also be caused by bacterial infections. This makes cat flu more of a general term for infections involving a cat’s upper respiratory system.

Feline Herpesvirus

Feline herpesvirus, also known as FHV-1, is a highly contagious virus that targets a cat’s upper respiratory system. It primarily affects the eyes, nasal passages, and throat. Once infected, the virus can cause serious issues other than cat flu.

The virus causes multiple problems, such as corneal ulcers, conjunctivitis, and other eye problems in cats. Be sure to look out for your cats as the virus can spread from one cat to another easily, especially in crowded areas.

Feline Calicivirus

Feline calicivirus is another major cause of cat flu, affecting the respiratory tract and oral health. The virus comes in multiple strains, with some causing mild symptoms and others leading to severe, systemic illness. These strains can also affect the joints and kidneys.

The virus will mostly stay on the lining of the cat’s mouth. After replicating, it can spread to other organs. This can cause sneezing, nasal discharge, fever, and drooling. In more severe cases, cats may experience joint pain or pneumonia.

FCV is remarkably resilient and capable of surviving in the environment for extended periods. Cats can easily contract the virus from direct contact and contaminated items.

Chlamydia felis

Chlamydia felis is a bacterial pathogen that can cause cat flu, with conjunctivitis as an accompanying symptom. Cats infected with C. felis often have red, swollen eyes with watery or thick discharge. 

It can also contribute to problems in the upper respiratory symptoms, gastrointestinal tract, and reproductive tract. The bacterium generally spreads through direct contact.

Bordetella bronchiseptica

Although more commonly associated with kennel cough in dogs, Bordetella bronchiseptica can also infect cats, particularly in crowded settings such as shelters or catteries. 

Bordetella bronchiseptica is highly contagious, which means the bacteria can easily spread through respiratory droplets. Cats can also get them from infected dogs.

How Can Cats Have the Flu?

Cat flu is a highly contagious disease, meaning all cats are at risk. Take note of the ways the disease spreads:

Direct Contact

Physical interactions are a common way for cat flu to spread. This includes activities such as grooming, playing, or nuzzling. Plus, an infected cat's secretions, like their saliva and nasal discharge, can transmit the disease.

Airborne droplets can also be modes of transmission, as whenever an infected cat coughs or sneezes, the pathogens can reach another healthy cat. 

Contaminated Objects

Transmission doesn’t stop at direct contact. Cats can also get infected when they use items that have been used by infected cats. The pathogens that cause cat flu can remain on environmental surfaces, shared spaces, and common items. 

When healthy cats come into contact with these objects and places, they can get infected.

Human Contact

The disease can also spread through human contact. When cats touch our hands, items, or clothes, we can potentially spread the pathogen to them. This happens when handling other infected cats. 

What Are the Symptoms of Cat Flu?

Since the disease targets the upper respiratory system of cats, expect the symptoms to mostly cover this area. 

• Coughing and Sneezing. One of the most noticeable signs of cat flu is through respiratory symptoms. Cats with the flu can have persistent coughing and sneezing. These indicate irritation.

• Nasal Discharge and Congestion. A runny nose and blocked nasal airways are often common symptoms of cat flu. Some can even wheeze when their nasal passageways are severely blocked. 

• Eye Issues. Eye-related symptoms are to be expected with infections caused by feline herpesvirus or Chlamydia felis. Cats may develop conjunctivitis, which causes redness, swelling, and discharge from the eyes. Some cats may have discharge as well. 

• Fever and Lethargy. Lethargy in cats with the flu is common, so expect them to be less playful and more inclined to rest. Many cats can also come down with mild to moderate fever.

• Loss of Appetite. Cats with flu often lose their appetite due to a combination of nasal congestion and oral discomfort. As a result, dehydration and weight loss are inevitable.

• Oral Pain. Mouth ulcers caused by feline calicivirus often result in excessive drooling. Cats may also paw at their mouth or show signs of oral pain, such as avoiding hard food or refusing to eat altogether.

• Behavioral Changes. Cats suffering from the flu may show subtle behavioral changes. Because of the stress and discomfort they experience, they’ll be grooming less and might seek to hide in solitude. Other cats might also become clingy and vocalize more.