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5 Common Viral Infections in Kittens


By Leslie Ingraham

Published: 02/01/2022, edited: 02/01/2022

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Kittens, especially those in shelters and feral colonies, are particularly susceptible to viral infections. Due to a still developing immune system, a severe viral infection can quickly overwhelm a young kitten's body. And while vaccinations given to kittens during their first year of life can help to protect them against some of these infections, in some cases, they may only lessen symptoms if the kitten catches the actual viral infection. 

Whether you are caring for newborn kittens, or have adopted one into your home, knowing how to spot signs of an infection can make all the difference in your feline's health and recovery. Read on to learn more about the 5 most common viral infections that affect kittens.


Cats and kittens who spend time outdoors may come into contact with animals infected with the rabies virus. Rabies affects a kitten’s brain and spinal cord, and the condition is almost 100 percent fatal. Most often it’s the result of a bite, but even another animal spitting or hissing can result in an infection. Saliva can enter their mucous membrane or an open wound like a scratch. In the U.S., more cats are reported with rabies than other animal species. Rabies can spread quickly among unvaccinated kittens in a shelter or feral colony.


Most of the symptoms of rabies are related to the central nervous system. They include:

  • Changes in behavior, such as aggression, lethargy, or restlessness

  • Fever

  • Reduced water consumption

  • Increased vocalization

  • Loss of appetite

  • Excessive salivation

  • Weakness 

  • Disorientation

  • Paralysis

  • Seizures

  • Sudden collapse and death


Rabies is caused by the entry of the rabies virus into the kitten’s body, most often from a bite by an infected animal, although transfer of saliva from spitting and grooming can also cause it. 


Unfortunately, there is no accurate test to detect rabies in a live animal. Diagnosis is made through observation during a 10-day quarantine. The virus can incubate in the animal’s body for up to a year after infection, and the animal doesn’t have to exhibit symptoms to be contagious.

The only way to know if a kitten has succumbed to rabies is a test performed after death, called a fluorescent antibody test. It identifies the antibodies produced once the kitten is infected.


Once symptoms appear, there is no cure or treatment. A veterinarian will recommend euthanasia in confirmed cases. Euthanasia is mandatory in some states and municipalities. 

The medication used to treat human rabies exposure is not available for cats. The only way to prevent your kitten from becoming infected is with a rabies vaccine and boosters. Your vet will know when and how often to administer the vaccine during the kitten’s first year and thereafter.

Average cost of treatment: $150 - $500

Feline Panleukopenia

Feline panleukopenia is also sometimes called feline distemper or feline parvo. It is caused by the feline parvovirus, which infects and kills cells in the developing fetus, bone marrow, lymph nodes, and intestines. It exists everywhere in the environment and is most often contracted by kittens three to five months of age who may already be fragile and unvaccinated. It results in a shortage of all types of white blood cells (panleukopenia) and red blood cells (anemia).

The virus can be found in a kitten’s secretions, such as urine and stool, as well as nasal secretions. Sometimes fleas can carry the disease. Surfaces like bedding, cages, food and water dishes and human hands and clothing may also transfer the virus to a kitten.


Symptoms of a panleukopenia infection are the result of damage to continually reproducing cells, and include: 

  • Vomiting

  • Decreased water consumption

  • Severe diarrhea

  • High fever

  • Loss of appetite

  • Nasal discharge

  • Dehydration

  • Lethargy

  • General depression

The high fever may drop to lower than normal just before death. An infected pregnant cat may abort their fetuses, or birth kittens that suffer damage to the brain and eyes. The brain damage is called feline cerebellar ataxia, which causes severe tremors when the kitten moves. 


Infection by the feline parvovirus is the cause of feline panleukopenia. Because it’s so prevalent in the environment, kittens made susceptible by poor nutrition, exposure to the elements, or other diseases are common victims.  


The symptoms of feline panleukopenia resemble those of other conditions, making a diagnosis difficult. Blood tests will indicate a severe reduction in the amount of all white blood cells, leaving the kitten with little immunity to secondary infections. A stool sample is examined for the presence of the parvovirus. However, if a kitten has had a recent vaccination against the parvovirus, a stool sample may show a false positive. 


The first step in the treatment of feline panleukopenia is the isolation of the affected kitten to prevent cross-infection. Subsequently, the treatment regimen includes supportive care. This could include administering antiemetic or antidiarrheal medications, antibiotics to prevent secondary bacterial infections, or drugs to bring the fever down, as well as intravenous fluids for dehydration and nourishment. Kittens less than eight weeks old often have a poor prognosis. There is a feline vaccine available to prevent feline panleukopenia, and kittens receive it during their first few months of life. 

Average cost of treatment: $500 - $2,000

5 Common Viral Infections in Kittens

Feline Calicivirus Infection (FCV)

FCV is a highly contagious respiratory infection that often infects young kittens. It causes a mild to severe upper respiratory infection and oral disease. The condition is especially common in shelters, pet stores, and breeding colonies. While most kittens recover fully, there are rare viral strains that can prove deadly. FCV is not a threat to humans. 

A complication of feline calicivirus infection caused by a rare mutant strain is called FCV-associated virulent systemic disease (FCV-VSD). This condition is characterized by damage to multiple organs and often death.


Symptoms of the feline calicivirus depend on the strain and can range from mild to severe. Mild infections resemble a cold and last from five to ten days. Symptoms include:

  • Sneezing

  • Nasal congestion

  • Fever

  • Copious discharge from nose and eyes

  • Drooling

Severe calicivirus infections can last up to six weeks, and is most severe in young kittens and elderly cats. Opportunistic bacterial infections are common. In addition to the mild case symptoms, a severe infection can also cause:

  • Inflammation and ulcers on the tongue and lining of the mouth

  • Lethargy

  • Mild lameness

  • Lack of appetite

  • Weight loss


Feline calicivirus is caused by an infection of the virus. Infected cats normally shed the virus for two to three weeks after infection, and some cats become long-term carriers. This hardy virus can live on surfaces for up to a month. A kitten can become infected with the virus in several ways:

  • Direct contact with another animal infected with the virus. 

  • Contact with infected saliva, nasal mucus, eye discharge and airborne droplets caused by sneezing that are spread from an infected feline. 

  • Contact with infected urine, feces or blood.

  • Humans can transfer the virus to kittens after handling a cat or kitten with it, even if the feline is showing no symptoms


Feline calicivirus is diagnosed primarily by a physical examination and thorough medical history. Signs and symptoms are identified to determine the condition and its level of severity. The veterinarian may also take swab samples of the kitten’s eyes, nose, or mouth to detect the presence of the virus. If the vet suspects pneumonia, an x-ray may be performed to confirm it.


Treatment for calicivirus is largely supportive and can include intravenous fluids for dehydration and nourishment and oxygen therapy. Several medications are used to treat this virus, including fever-reducing medication, antihistamines, antibiotics for secondary bacterial infections, pain medication, and anti-inflammatory drugs. Most kittens recover completely with supportive care, but some infections result in chronic gingivitis with painful, inflamed gums that cause difficulty with eating. Soft, slightly warmed foods may help to make eating more comfortable for these kitties.

Average cost of treatment: $200 - $500

Intestinal Viral Infection

Intestinal viral infections in kittens cause inflammation of the lining of the intestines leading to diarrhea and upset stomach. It can occur in a cat of any age, but it is most common in young kittens and can be particularly severe and life-threatening in this population. The viruses that cause these infections can be passed to humans, and kittens with symptoms should be isolated from people, especially young children and elderly adults.


While adult cats may not have visible symptoms of an intestinal viral infection, kittens typically present with:

  • Mild to severe watery, abnormally colored diarrhea 

  • Loss of appetite

  • Vomiting

  • Severe weight loss

  • Fever

  • Abdominal pain

  • Dehydration

  • Nasal discharge

  • Watery eyes


Viral intestinal infections are most commonly caused by four common viruses:

  • Rotavirus

  • Parvovirus

  • Astrovirus

  • Coronavirus

Intestinal viral infections in kittens are very contagious. Transmission is through contact with an infected cat or kitten’s saliva or feces, and an infected mother cat can pass it to their offspring. It occurs frequently in places with many cats in small areas such as shelters, feral colonies, pet stores, and breeding colonies. The virus can live on surfaces such as bedding and litter boxes, as well as in food. Humans can pass it from kitten to kitten on their hands and clothing. Infected cats who may show mild or no symptoms may shed the virus from one month to two years.


A thorough history of symptoms followed by a physical examination are the primary diagnostic tools when a symptomatic kitten is brought to the clinic. The main focus is to rule out other causes before arriving at a viral infection diagnosis. Other causes may include parasites, tumors, other bacterial or viral infections, ingestion of poisons or other toxic materials, or food allergies.  

Blood tests will help to evaluate a kitten’s overall health, along with stool samples to determine if the infection is viral or bacterial. Stools may also demonstrate the presence of parasites and traces of toxic materials. Imaging tools such as x-rays and ultrasound may be used to visualize the abdominal cavity, along with direct viewing through endoscopy.


Treatment centers on relief of symptoms and supportive care, such as intravenous fluids to address dehydration and nourishment deficits, and antiemetic or antidiarrheal medications. Additionally, an easily digestible, high-protein diet to support healing may also be prescribed.

Average cost of treatment: $500 - $4,000

Feline Leukemia Virus (FeLV)

Feline leukemia virus is one of the most common causes of illness and death in cats and kittens. Kittens are much more susceptible to the condition, and can contract it from their mothers. The virus acts on the kittens’ immune systems to inhibit the ability to fight off infections and cancer. 


Symptoms may be mild to severe, and can include:

  • Appetite loss

  • Weight loss

  • Dehydration

  • Enlarged lymph nodes

  • Diarrhea

  • Fever

  • Poor coat condition

  • Pale gums and other mucus membranes

  • Secondary infections in the urinary tract, skin and upper respiratory tract

  • Behavior changes

  • Seizures and other neurological disorders

  • Eye conditions with discharge 

  • Reproductive failure (abortions, premature birth)

  • Jaundice


Contact with an infected cat is the primary cause of feline leukemia in kittens. Infected mother cats can pass it along to their kittens while in the uterus, during birth, or when grooming and nursing. FeLV is common in environments with multiple cats such as shelters and feral colonies. The virus is shed in the saliva, urine, feces, and nasal discharge of infected cats. It can also be caused by a bite or scratch, and less often from surfaces such as food bowls and litter boxes. The virus will live outside a cat’s body for only a few hours.


Screening for FeLV is commonly performed in a veterinarian’s office, using a test called an enzyme-linked immunosorbent assay (ELISA) that detects a specific protein found in the virus. A second test is indirect immunofluorescent antibody assay (IFA) which is done in a lab. The IFA test confirms the presence of the virus in white blood cells. In some cases, your veterinarian will recommend a third test that identifies whether the virus has infected the bone marrow. This is called a polymerase chain reaction (PCR) test.

A complete physical exam and symptom history will detect signs of the disease in kittens, although older cats may not display symptoms. Asymptomatic cats can still shed the virus, sometimes for life.


There is no cure for FeLV, but treatment is aimed at specific issues caused by the virus such as anemia or secondary infections. Treatment may include blood transfusions, intravenous therapy, supportive care to alleviate discomfort and support the kitten’s immune system, and isolation of infected cats. Antibiotics for secondary infections may be prescribed, as well as antidiarrheal or appetite-stimulating medications. A vaccine is available to prevent the condition in uninfected kittens.

Average cost of treatment: $200 - $1,000

Be prepared for anything

Viral infections in kittens can be expensive to treat. If you suspect your kitten is at risk of a viral infection, start searching for pet insurance today. Wag!’s pet insurance comparison tool lets you compare plans from leading companies like PetPlan and Embrace. Find the “pawfect” plan for your pet in just a few clicks!

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