Cats Flu, Upper Respiratory Tract Infection

kitten with conjunctivitis

can cats get the flu

Cat flu or upper respiratory tract infection (URI) may be a quite common disease that will vary considerably in severity, and on occasions can even be life-threatening.

In the overwhelming majority of cases, disease results from infection with feline calicivirus (FCV) or feline herpes (FHV, or FHV-1). Clinical signs include sneezing, nasal discharge, conjunctivitis (inflammation of the liner of the eyes), ocular discharge, loss of appetite, fever, and depression. Mouth ulcers, coughing, excessive drooling of saliva, and eye ulcers can also be seen. Very young, very old, and immunosuppressed cats are more likely to develop severe disease and possibly die as a result of their URI, usually thanks to secondary infections (such as pneumonia), lack of nutrition, and dehydration.

What cats are in danger of URIs?

URIs are common because the causative viruses are widespread in cat populations. Typical risk factors include:

Cats kept in large groups or colonies like breeding catteries, rescue centers, and feral cat colonies – in these situations the viruses are ready to spread easily

Elderly and immunosuppressed cats (e.g., cats with FeLV or FIV infection, or cats receiving immunosuppressive therapy) are more susceptible to developing severe disease

Causes of URIs in cats

Most cat URIs are caused by infection with one or both of the cat flu viruses:

Feline herpes (FHV or FHV-1, formerly referred to as feline rhinotracheitis virus)

Feline calicivirus (FCV)

These two viruses are thought to be liable for quite 90% of URIs in cats. Other important organisms which will be involved in some cases include:

Bordetella (may be an explanation for sneezing, nasal discharge and sometimes coughing – important in some colony situations)

Chlamydophila felis (this is especially an explanation for ocular disease – conjunctivitis)

Clinical signs of URI

The period following infection with FCV or FHV is typically just a couple of days (2-10 days). After this, typical clinical signs develop which include:

  • Sneezing
  • Nasal discharge
  • Ocular discharge
  • Lethargy
  • Inappetence
  • Fever
conjunctivitis feline

The severity of those signs varies considerably – in some cats, the signs are very mild and transient, in others, they’ll be very marked and severe. There are some differences in clinical presentation between the 2 viruses, but these aren’t sufficient to be ready to distinguish them simply from clinical signs:

FHV infection tends to be more severe, often causing more marked conjunctivitis (eye infection and ocular discharge), and a few ulceration of the cornea (the clear part at the front of the eye). FHV can also cause severe pharyngitis resulting in anorexia; inflammation within the trachea; and coughing.

FCV infection is usually milder, with inapparent or less severe ocular signs, but FCV often causes ulceration of the tongue (and sometimes the palate or the lips). FCV may cause transient arthritis (‘limping syndrome’), usually seen in young kittens, and very young kittens can cause a severe viral infection.

Although FCV and FHV are viral infections, secondary infection with bacteria is common and may contribute to rhinitis (infection within the nose) conjunctivitis, and even lung infections. While most cats will get over URIs, on occasions they will be life-threatening, and with severe infections, the recovery may take several weeks. Some cats can also be left with permanent damage within the nose and should have persistent or recurrent nasal discharge (so-called ‘chronic rhinitis’).

In rare cases, a way more severe and sometimes fatal sort of FCV infection may occur. this is often related to particular strains of the virus that are highly virulent and termed ‘virulent systemic FCV’ (vsFCV) infection. Fortunately, such infections are very rare (see: Feline calicivirus (FCV) infection).


Diagnosis by your vet is typically supported by the standard signs related to URIs, and exclusion of other causes. it’s possible to verify a diagnosis and to research which virus(es) are involved, but this is often not necessary.

Testing for FCV or FHV involves collecting a mouth or eye swab which is then sent to a specialized veterinary laboratory. Here the virus is often identified through culturing or by a PCR test (a molecular test to point out the presence of the viral genes).

cat weight


Treatment of URIs is essentially symptomatic and supportive. Your vet might want to try some additional tests if they’re concerned about the extent of disease (e.g., the likelihood of pneumonia) or if they’re worried about complications (such as infection with FIV or FeLV).

Antibiotics are indicated to treat secondary bacterial infections and to undertake to scale back the damage the infection causes. If nasal congestion is severe and breathing is difficult your vet can also suggest steam inhalation or nebulization make discharges more liquid and more easily relieved by sneezing.

Interferons are proteins that are produced within the body, partially to assist fight viral infections. Injectable interferons could also be used as a supportive treatment (either high doses of recombinant human interferons or recombinant feline interferon) – there’s some evidence that this might be of benefit, but it probably must tend early within the course of disease for best effect.

There are a variety of topical antiviral agents that will help to manage FHV-associated ocular disease (such as trifluridine, idoxuridine, and cidofovir). More recently a drug wont to treat human herpes infections – famciclovir – is safe and effective in cats when given orally. this is often a serious breakthrough in managing severe FHV infection in cats.

General nursing is additionally essential – discharges from the eyes and nose should be gently wiped away using damp cotton, and therefore the cat should be kept warm and cozy.


Most cats that get over infection with URI viruses will become ‘carriers’. Carrier cats usually show no sign of illness but, may shed virus in saliva, tears and nasal secretions, and maybe a source of infection to other cats.

Although most cats infected with FHV will remain long-term carriers, many of those will never shed significant amounts of virus. Others may shed virus intermittently, especially during times of stress. Some cats may show mild signs of URI again once they shed the virus, but most don’t. Carrier cats during a breeding colony are a source of risk to their kittens, because the stress of kittening may induce shedding of FHV.

Most cats infected with FCV remain carriers of the virus, and still shed the virus for weeks or months after infection, but the bulk (although not all) will eventually eliminate the virus within a couple of months.

Spread of infection

cat viruses

The viruses related to URIs are spread in three ways:

Direct contact with an infected cat showing signs of URI

Direct contact with a carrier cat shedding virus

Contact with a virus carried on clothing, food bowls, and other objects. Large amounts of viruses are present within the saliva, tears, and nasal discharges, and therefore the viruses could also be ready to survive within the environment and on objects for up to 2 (FHV) to 10 (FCV) days.


Vaccination: the danger of URIs are often dramatically reduced by vaccination against FHV and FCV. These vaccines are important for all cats, regardless of how they’re kept (even if kept indoors) because the diseases are so ubiquitous. Although vaccination usually prevents severe disease development, it cannot always prevent infection occurring then mild disease should develop in some cats. FCV has many various strains, and this will cause further problems with vaccination as vaccines won’t necessarily work against these strains. Newer FCV vaccines contain quite one strain within the vaccine to assist overcome this problem. this is often not a problem with FHV as just one virus strain exists.

Barrier nursing and disinfection: If there’s quite one cat during a household, it’s important to undertake to minimize the danger of infection being spread to the opposite cats. this is often not always possible, but additionally to make sure that each one cat is vaccinated, where possible a cat showing clinical signs should be kept isolated from the opposite cats (e.g., confined to at least one room). Separate food bowls and litter trays should be used, and ideally, the cat should be kept during a room that has very easy to disinfect surfaces (i.e., not soft furnishing and carpet). These viruses are vulnerable to most disinfectants but confirm you ask your vet – some disinfectants (such as phenolic-based products) aren’t safe to use around cats. Hypochlorite (bleach-based) disinfectants (eg, 5% bleach diluted 1:32) are effective against these viruses, but lookout to use any disinfectant carefully – most are irritant to cats if they are available into direct contact with the disinfectant cat litter.

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