Cat Fever in Humans. Everything You Need to Know About This Strange Illness

What is Cat Fever?

Cat fever, also known as cat scratch disease, is an illness caused by the bacteria Bartonella henselae. It is transmitted between cats and humans, typically when a person is scratched, bitten, or exposed to the saliva of an infected cat. The disease results in fever and enlarged lymph nodes in humans (Merriam-Webster Medical, 2022).

Cat fever is characterized by a respiratory infection accompanied by fever, which is why it has historically been known as “cat fever”, especially in the United States Navy. It is not technically a true fever limited to cats, but rather a zoonotic bacterial disease that can spread between cats and humans. The Bartonella henselae bacteria is the primary cause of cat scratch disease in both felines and human patients (Merriam-Webster Medical, 2022).

Overall, cat fever refers to an illness transmitted from cats to humans and characterized by fever, respiratory infection, and swollen lymph nodes. It is caused by the Bartonella henselae bacteria and also known as cat scratch disease.

Symptoms in Humans

Cat fever symptoms in humans can appear 3-10 days after infection. Some of the most common symptoms include:

Swollen lymph nodes: The lymph nodes near the original scratch or bite will often become swollen, tender, and painful within 2 weeks of the initial skin infection. This is one of the classic symptoms of cat fever in humans. The swelling occurs as the lymph nodes produce more infection-fighting white blood cells (source:

Fever: Low-grade fevers, usually below 102°F (39°C), frequently occur with cat fever. Fatigue and body aches often accompany the fever (source:

Fatigue: Excessive tiredness and lethargy are common during the acute phase of cat fever. The fatigue results from the body’s immune response (source:

Headaches: Mild to moderate headaches often accompany the fever and fatigue. Headaches seem to be more common in adults than children (source:

Sore throat: Some people with cat fever develop a sore, scratchy throat. However, this is less common than the other symptoms (source:

The initial symptoms usually resolve within 2-3 weeks without treatment in healthy individuals. However, some people may experience recurring symptoms over several months. Seek prompt medical care for severe or persistent symptoms.

How Humans Get Infected

Cat fever in humans is caused by a bacterial infection transmitted by cats. The bacteria, Bartonella henselae, is spread to humans through scratches, bites, or exposure to the saliva of an infected cat, especially through claws contaminated with flea feces.

When an infected cat grooms itself, it ingests fleas and flea feces containing the bacteria. If the cat then scratches a person, its claws can introduce the bacteria into the wound. Transmission can also occur if the cat bites a person, exposing them to bacteria in the cat’s saliva.

Simply petting or handling an infected cat is unlikely to spread the bacteria. However, any situation where a person comes into contact with an infected cat’s saliva, scratches, or bites can potentially transmit the infection. Kittens under 12 months of age are more likely to transmit the disease.

To minimize risk, it is important to regularly use flea control products on cats. Promptly cleaning any cat scratches or bites with soap and water can also help prevent infection.


To diagnose feline infectious peritonitis (cat fever), veterinarians will start with a complete physical exam of the cat. They will check the cat’s lymph nodes, feeling for any swelling that could indicate infection. The veterinarian will also listen to the cat’s chest with a stethoscope to check for fluid buildup in the lungs, which can occur with cat fever.

In addition to the physical exam, the veterinarian will likely run blood tests. These can help detect antibodies related to cat fever, indicating whether the cat has been exposed to the feline coronavirus that causes the disease. Blood tests can also show organ inflammation and look for an elevation in protein levels, which are common in cats with cat fever.

If initial testing is inconclusive, the veterinarian may recommend more specialized tests. This can include imaging such as X-rays, ultrasounds, or MRIs to check for fluid accumulation. They may also perform a biopsy of tissue to check for the viral antigens related to cat fever under a microscope. These additional tests help confirm a diagnosis when symptoms indicate cat fever but initial bloodwork is unclear.


Cat fever usually resolves on its own within a few days as the cat’s immune system fights off the infection. Severe or persistent fevers may require antibiotics prescribed by a veterinarian to treat the underlying infection. There is no over-the-counter medication specifically for treating fever in cats.

Treatment is focused on making the cat comfortable and allowing the fever to run its course. This includes ensuring the cat rests, stays hydrated, and eats as normally as possible. Cooling measures like wet towels can help lower a high fever temporarily. It’s important not to give human fever reducers like acetaminophen to cats, as these can be toxic.

Cats should see a vet if the fever persists more than 1-2 days or is over 104°F. Respiratory distress, lethargy, or other concerning symptoms also warrant medical attention. With appropriate care, most cats recover fully from fever within a week.


There are several ways to prevent cat scratch disease. The most obvious is to avoid scratches and bites from cats (CDC). Keeping cats indoors and away from wildlife can reduce the risk of flea infestations and fights with other cats. When handling cats, wear thick gloves to prevent scratches. If scratched or bitten, promptly wash the area with soap and water.

It’s also important to control fleas on pet cats. Fleas can transmit Bartonella bacteria between cats. Work with your veterinarian to use safe and effective flea control products. Vacuum areas cats frequent to remove eggs and larvae.

Be sure to wash your hands with soap and water after playing with, petting or handling cats. Avoid touching your face or eyes until after handwashing. Teach children proper hygiene after interacting with cats.

Risk Factors

Some people are at higher risk of developing cat fever than others. This includes:

  • Children – Cat fever is more common in children, likely due to their still-developing immune systems.
  • Immunocompromised individuals – Those with weakened immune systems, such as people with HIV/AIDS, cancer patients undergoing chemotherapy, transplant recipients taking immunosuppressant drugs, and people taking steroids long-term, are at increased risk for cat fever.

People with compromised immune function have a harder time fighting off infections like Toxoplasma gondii. Young children’s immune systems are also not yet fully matured. Both of these groups are more susceptible to developing cat fever if exposed to the parasite.


While cat fever rarely spreads from the respiratory tract to other parts of the body, complications can occasionally occur. These include spread to the liver, spleen, eyes, bones and brain, although such disseminated infections are uncommon (source).

When cat fever does spread beyond the respiratory system, it is usually to local lymph nodes first. From there it may disseminate via the bloodstream to other organs. However, most cases remain localized in the upper respiratory tract and do not become systemic (source).

Overall, complications from cat fever are rare. While concerning if they do occur, the infection is generally mild in humans and often resolves on its own or with supportive treatment (source). Severe disseminated infections are uncommon.


The prognosis for cat scratch fever is excellent. Fatalities from cat scratch fever are extremely rare. According to the CDC, cat scratch disease usually resolves on its own without antibiotic treatment in healthy people. The infection typically lasts 2 to 4 months, but most symptoms start improving within just a few weeks. Only about 5-14% of lymph node infections will result in chronic lymph node infections lasting more than 6 months. In rare cases (less than 1% of infections), cat scratch fever can lead to complications like encephalitis, endocarditis, or parinaud oculoglandular syndrome if Bartonella spreads to other parts of the body from the initial infection site. However, complete recovery is expected even from these rare complications in healthy individuals. Overall, cat scratch fever has a mortality rate close to zero when treated properly. By comparison, the CDC states there has been a mortality rate of 0.4% from bartonella endocarditis, which can arise from untreated cat scratch fever spreading to heart valves. So while very serious complications can arise, they remain extremely rare, and most people who acquire cat scratch fever can expect a full recovery within a few months at most.


Cat fever, also known as cat scratch disease, is usually a mild illness in humans that resolves on its own. The infection is caused by a bacterium called Bartonella henselae which is spread to humans through bites, scratches, or saliva from infected cats. The most common symptoms are swollen lymph nodes around the head, neck or arm, fever, headache, fatigue, and loss of appetite. More serious complications like encephalitis can occur but are rare.

To avoid getting infected, take precautions against cat scratches and bites. See your doctor if you develop symptoms suggestive of cat fever, especially if they persist beyond 1-2 weeks. With rest and symptom management, most people recover fully within 2-4 months. While antibiotics are not routinely used, they may be indicated for more severe cases. The prognosis is generally good, but some patients can experience lingering fatigue even after the infection clears.

In summary, cat fever is usually a mild, self-limiting illness in humans. Avoiding scratches and bites from cats, and seeing a doctor for persistent symptoms, are the keys to dealing with this infection. With proper care, most people recover fully.

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