Cat Flu Antibiotics. What Works Best for Your Feline Friend

What is Cat Flu?

Cat flu is a common upper respiratory infection in cats that is similar to the common cold in humans. It is sometimes also referred to as feline viral rhinotracheitis or feline herpesvirus. According to Cats Protection UK, cat flu is caused by several viruses that affect a cat’s upper respiratory tract, including the nose, throat, windpipe and sometimes the eyes.

The most common viruses that cause cat flu are:

  • Feline herpesvirus type 1 (FHV-1)
  • Feline calicivirus (FCV)

These viruses are extremely contagious and spread through direct contact between cats, on surfaces, or in the air through sneezing and coughing. According to the CDC, most cats with cat flu experience symptoms within 2-6 days of exposure.

Common symptoms of cat flu include sneezing, runny nose and eyes, fever, lethargy, loss of appetite, and ulcers in the mouth. In severe cases, pneumonia can develop. While many cats recover fully, some develop chronic infections and may continue to spread the virus to other cats.

Common Causes

The most common causes of cat flu are viral infections from feline herpesvirus, feline calicivirus, and bacterial infections from Chlamydophila felis. These pathogens are highly contagious and easily spread between cats through direct contact, saliva, nasal secretions, and contaminated surfaces or objects.

Feline herpesvirus is responsible for about 80% of cat flu cases. It targets a cat’s upper respiratory tract, causing symptoms like sneezing, nasal discharge, fatigue, fever, and eye infections. The virus remains dormant in a cat’s body even after recovery, leading to potential flare-ups when the immune system is compromised (Cat Flu: Symptoms, Treatment, and Prevention).

Feline calicivirus accounts for about 15% of cases and also infects the respiratory tract. Common symptoms include oral ulcers, limping, and pneumonia. It is highly contagious and can spread through shared food bowls, grooming items, or litter boxes (Cat Flu | Symptoms, Causes, and Treatment).

The bacterium Chlamydophila felis triggers respiratory infection in cats, causing lethargy, fever, and ocular and nasal discharge. Young kittens are particularly susceptible. Without treatment, the bacteria can penetrate more deeply into the lungs (Feline Upper Respiratory Infection (Cat Flu)).


Diagnosing cat flu involves a thorough physical exam, medical history, and diagnostic tests. The veterinarian will check for common symptoms like sneezing, nasal discharge, fever, lethargy, loss of appetite, and conjunctivitis (eye discharge). They will also examine the mouth, ears, and throat for ulcers, inflammation, and discharge. The medical history provides insight into potential exposure to infected cats and whether vaccines are up to date.

Diagnostic tests may include:

  • Blood work to check for elevated white blood cell count indicating infection
  • Nasal swabs, conjunctival swabs, or pharyngeal swabs to test for viral presence
  • Radiographs (x-rays) to check for pneumonia

While tests can identify the specific virus, the clinical signs usually make diagnosis clear even without lab tests. Treatment often proceeds based on symptoms since many cats have complex infections with multiple viruses involved (Blue Cross).


There is no specific antiviral treatment for cat flu. Antibiotics may be prescribed by a veterinarian to treat secondary bacterial infections that can occur with cat flu, according to Blue Cross [1]. Common antibiotics used include doxycycline, amoxicillin, or clavamox [2]. Antibiotics are given for 7-10 days depending on the severity of symptoms.

Supportive care is also an important part of treatment. This includes ensuring the cat stays hydrated by encouraging eating and drinking. Appetite stimulants may be prescribed. Nasal decongestants can help open nasal passages for easier breathing. Nebulization helps open airways and loosen mucus. Cats with mouth ulcers may need soft foods. Keeping the cat in a quiet, warm area helps them rest and recover.

While antibiotics treat secondary infections, there are no antiviral medications that can cure the primary viral infection causing cat flu. Treatment focuses on managing symptoms and preventing complications while the cat’s immune system fights the virus [3]. Most cats recover fully in 2-4 weeks with appropriate supportive care and antibiotics if needed.


Recommended Antibiotics

The most common antibiotics used to treat cat flu are doxycycline and azithromycin. These are broad-spectrum antibiotics that are effective against the bacteria that commonly cause secondary infections in cats with flu (Source).

Doxycycline is commonly prescribed by vets to treat bacterial infections associated with cat flu. It is given orally and treats respiratory infections caused by Mycoplasma species and Chlamydophila. Doxycycline helps reduce nasal discharge and makes cats feel better more quickly (Source).

Azithromycin is another antibiotic option that is effective against Mycoplasma, Chlamydophila, and Bordetella species – common bacteria involved in cat flu infections. It is given orally and helps treat and prevent pneumonia. Azithromycin also has anti-inflammatory effects that can help reduce symptoms of upper respiratory illness in cats.

The dosage and length of antibiotic treatment depends on the severity of the infection and will be determined by a veterinarian. In mild cases, a short 5-7 day course is typical. More advanced infections require a longer treatment duration of 2-4 weeks. Antibiotics are most effective when paired with proper supportive care and rest.


The recommended dosage of antibiotics for cat flu depends on the weight of the cat and severity of symptoms. Amoxicillin is commonly prescribed at a dose of 22 mg/kg given orally every 12 hours (1, 2). For a 5 lb cat, this would equate to about 50 mg twice daily. Doxycycline is another option, given at a dose of 5 mg/kg once daily.

For severe upper respiratory infections, injectable antibiotics may be used initially, such as ceftazidime (20-40 mg/kg IV or IM every 12-24 hours) or enrofloxacin (5 mg/kg SQ once a day) (1). However, oral antibiotics are usually transitioned to quickly.

The typical course of antibiotics is 10-14 days but may need to be extended to 4 weeks for persistent infections. Cats should show improvement within 2-3 days on appropriate antibiotics. Close follow up with a veterinarian is recommended to monitor response.

Length of Treatment

When treating cat flu with antibiotics, the typical length of treatment is 7-14 days.1 Antibiotics help address any secondary bacterial infections that may develop and provide symptomatic relief, so it’s important to follow through with the full course as prescribed by your veterinarian. Usually about 5-7 days of antibiotics are necessary before improvement is seen. Some vets may prescribe a longer 10-14 day course to ensure the infection is fully resolved. It’s critical to complete the entire course as prescribed and not stop early, even if your cat seems better. Stopping antibiotics too soon can allow bacteria to persist and develop resistance. With a full treatment duration, your vet will ensure your cat’s cat flu is properly addressed.

Considerations When Treating Cat Flu With Antibiotics

When treating cat flu (feline upper respiratory infection) with antibiotics, it’s important to work closely with your veterinarian and follow their directions carefully. Here are some key considerations:

Work with your vet to determine the appropriate antibiotic and dosage based on your cat’s symptoms and the suspected underlying cause of infection. Antibiotics commonly used for cat flu include doxycycline, azithromycin, and amoxicillin (VCA Animal Hospitals). Your vet may prescribe an antibiotic shot or oral medication.

Follow your veterinarian’s instructions carefully in terms of dosage amount and schedule. It’s important to give antibiotics exactly as directed and for the full course of treatment, usually 5-14 days. Don’t stop early even if your cat seems better.

Monitor your cat closely over the treatment period. Look for improvements in symptoms like discharge from nose/eyes, sneezing, coughing, fever, and lethargy. Contact your vet if symptoms get worse or don’t improve within a few days of starting antibiotics.

Let your vet know right away about any side effects like vomiting, diarrhea, or lack of appetite. Your vet may adjust the medication type or dose.

Schedule a follow-up vet visit at the end of the antibiotic treatment period to confirm the infection has resolved. Additional medication may be needed if the infection persists.

With appropriate antibiotic treatment guided by a veterinarian, most cats fully recover from upper respiratory infections within 7-14 days.


Preventing cat flu involves taking measures to reduce exposure and boost the cat’s immune system. The most important prevention strategy is vaccination. Kittens should receive a series of vaccinations starting as early as 6-8 weeks old to protect against the main viral causes of cat flu such as feline herpesvirus and calicivirus. Annual boosters are recommended thereafter. While the vaccine doesn’t completely prevent infection, it reduces the severity and duration of symptoms if a cat does become infected. Vaccination is highly recommended for all cats, especially those with outdoor access who are at higher risk of exposure.

In addition to vaccines, good hygiene can help prevent spread of infection. Shared water and food bowls, litter boxes, and bedding should be thoroughly cleaned and disinfected regularly. New cats entering a household should be quarantined for at least 2 weeks and only allowed contact with resident cats after a vet exam confirms they are not infectious. Proper nutrition, reducing stress, and avoiding crowded conditions can help support a cat’s immune function. While total prevention is difficult, combining vaccination with good hygiene and care practices offers the best protection.


The prognosis for cats with cat flu is generally good, with most cats making a full recovery within 2-4 weeks (source). However, in some cases, cat flu can become chronic and difficult to fully resolve.

With supportive care at home and antibiotics if prescribed, the vast majority of cats will recover completely from cat flu. According to the Blue Cross, over 85% of affected cats will make a full recovery given appropriate treatment and time (source). The key is addressing any secondary bacterial infections with antibiotics and providing nutrition, fluids, and rest during the symptomatic period.

In a small percentage of cases, cats may experience lingering upper respiratory symptoms or eye discharge even after the main viral infection has resolved. Some cats can become chronic carriers of cat flu viruses and periodically suffer relapses. Cats with compromised immune systems may also have more persistent infections. In these situations, long-term medication may be required to manage the condition.

With attentive home care and veterinary oversight, the vast majority of cats fully bounce back from cat flu. But the illness can sometimes become chronic, requiring extended treatment. Overall, the prognosis is good for complete recovery, but cat flu can be challenging to completely cure in some cats.

Scroll to Top