Is Your Cat Infecting You? The Truth About Cat Scratch Disease


Cat scratch disease (CSD) is a bacterial infection primarily caused by Bartonella henselae bacteria. The infection is usually spread to humans through a bite or scratch from an infected cat. Symptoms of CSD include swollen lymph nodes, fatigue, fever, and alesions at the site of the scratch or bite. While most cases are mild and resolve on their own, complications can sometimes occur. The main question this article will address is whether CSD is actually caused by a virus or the Bartonella henselae bacteria.

According to the CDC, cat scratch disease is caused by a bacterium called Bartonella henselae (CDC – Cat Scratch Disease). B. henselae bacteria are found in the saliva of infected cats, and can be transmitted to humans through scratches, bites, or even just by handling an infected cat. Most people develop symptoms 3-14 days after exposure. The trademark symptom is enlarged lymph nodes near the site of the scratch or bite. Other symptoms may include fever, headache, exhaustion, and loss of appetite. In healthy individuals, symptoms usually resolve on their own within 2-4 months. However, complications can sometimes develop, especially in those with weakened immune systems.


Cat scratch disease is transmitted to humans primarily through scratches, bites, or licks from infected cats, especially kittens. The bacteria Bartonella henselae causes cat scratch disease and is spread through the saliva of infected cats. When an infected cat scratches, bites, or licks a person with an open wound, the bacteria can enter the skin and cause an infection.

Kittens are more likely to transmit the bacteria than adult cats, likely because their immune systems are still developing. Up to 40% of cats can carry the bacteria at some point in their lives. Cat fleas can also transmit the bacteria between cats. When an infected cat scratches or bites, its contaminated claws or teeth can introduce the bacteria into the wound. The cat’s saliva can also carry the bacteria.

While scratches and bites are the most common modes of transmission from cats to humans, it is also possible for the bacteria to enter the body through the eyes, nose, or mouth after exposure to an infected cat. However, this is less common.

Proper wound care after interacting with cats can help prevent infection. It’s also important for cat owners to control fleas and regularly inspect their cats for fleas or wounds if a human in the household develops cat scratch disease.


The most common symptoms of cat scratch disease are swollen lymph nodes, fever, fatigue, and loss of appetite (CDC). The lymph nodes usually swell near the scratch or bite, often in the neck, armpit or groin. The swollen lymph nodes may develop 1–3 weeks after the injury and can persist for several weeks or months. Fever and fatigue often accompany the swollen lymph glands. Some people also experience headaches, poor appetite, and muscle aches. Less common symptoms include rashes and eye inflammation (Cleveland Clinic).

The infected scratch or bite site can appear swollen and red with round, raised lesions and pus. However, only about half of people remember being bitten or scratched by a cat before symptoms started (Johns Hopkins Medicine). While the infection usually resolves on its own,prompt diagnosis and care of the wound site is recommended.


While most cases of cat scratch disease are relatively mild, some potential serious complications can occur in a small percentage of patients. One such complication is encephalitis, which is an inflammation of the brain that can result in headaches, fever, confusion, seizures, and more severe neurological symptoms. Encephalitis from cat scratch disease is rare, occurring in less than 1-2% of patients, but can potentially be life-threatening if not properly treated [1].

Another potential complication of cat scratch disease is neuroretinitis, which is inflammation of the optic nerve and retina. Symptoms of neuroretinitis include blurred vision, seeing black spots, pain in the eyes, and vision loss. While concerning, most patients with cat scratch neuroretinitis recover their vision after antibiotic treatment [2].

Less commonly, the bacteria that causes cat scratch disease can spread to the bones, leading to osteomyelitis. This bone infection causes swelling, pain, and damage, usually occurring in the arms, legs, fingers, or toes. Osteomyelitis from cat scratch disease is relatively rare but may require prolonged antibiotics or surgery for treatment [3].

While serious complications are not the norm, it’s important to monitor for any concerning or worsening symptoms after a cat scratch or bite. Prompt medical care can help manage complications like encephalitis, neuroretinitis, or osteomyelitis from cat scratch disease.


Cat scratch disease is typically diagnosed through a combination of physical examination, patient history, and lab tests. If a doctor suspects cat scratch disease, they will first perform a physical exam of any skin lesions and check for swollen lymph nodes near the scratch or bite. They will also ask about any recent exposure to cats and symptoms that have developed. Blood tests can help confirm the diagnosis by detecting antibodies to the bacteria Bartonella henselae that causes cat scratch disease. This includes tests such as an indirect fluorescent antibody (IFA) assay. The initial blood test may be negative if done too soon after infection, so a follow-up test 2-8 weeks later may be needed. Lymph node biopsy is another diagnostic technique that can be used to detect the bacteria. This involves surgically removing part of an enlarged lymph node to examine it under a microscope and test for the presence of B. henselae. A lymph node biopsy allows doctors to definitively diagnose the disease in cases that remain uncertain after the initial workup. Along with looking for signs of the infection itself, biopsy results help doctors rule out other potential causes of the lymph node swelling such as lymphoma or other bacterial infections (Source).


Usually, cat scratch disease resolves on its own without the need for treatment. According to the American Academy of Family Physicians, most cases of cat scratch disease are self-limited and do not require antibiotics.

In severe cases, antibiotics may be prescribed to help manage symptoms and complications. The antibiotics azithromycin and doxycycline are sometimes used for this purpose. However, antibiotics do not appear to significantly speed recovery in uncomplicated cases of cat scratch disease.

Other treatments focus on relieving symptoms. These can include over-the-counter medications for pain and fever, warm compresses for lymph node swelling, and elevating the affected limb. In rare cases where severe complications develop, more aggressive treatments like surgery may be warranted.

Overall, the majority of people with cat scratch disease recover fully within a few months without antibiotics or other specific treatment, as the immune system clears the infection on its own.


The best way to prevent cat scratch disease is to avoid scratches and bites from cats, especially kittens. According to the CDC, it’s important to wash any cat scratches or bites gently with soap and water right away. Apply an antibiotic ointment as well to reduce the risk of infection. Supervise young children when playing with cats so they don’t get scratched or bitten. Avoid rough play with cats that could lead to scratches or bites. Also be careful when attempting to break up fights between cats.

Controlling fleas on cats is another prevention measure. Fleas can transmit the Bartonella bacteria between cats. Work with your vet to keep your cat on a regular flea prevention medication. Limit opportunities for your cat to roam outdoors and hunt, which also reduces flea exposure. Bring outdoor cats in at night when fleas are most active. Regularly comb and bathe cats to control fleas as well.

Keep cats indoors as much as possible to limit the risk of flea exposure. An indoor cat has a lower chance of contracting Bartonella bacteria. If there are stray or feral cats in your neighborhood, do not allow your cat to interact with them. This limits potential Bartonella transmission from unknown cats.


There are some common misconceptions about cat scratch disease that are important to address. First, despite the name, cat scratch disease is not caused by a virus. Rather, it is caused by a type of bacteria called Bartonella henselae. This bacteria can be carried by cats, especially kittens, and transmitted to humans through scratches, bites, or exposure to fleas from an infected cat. However, cat scratch disease is not contagious between humans. You cannot catch it from another person, only directly from an infected cat.

Another myth is that you can only get cat scratch disease from being scratched. In fact, bites and exposure to fleas from an infected cat can also lead to transmission of the bacteria. Additionally, some people assume that because it has the word “fever” in its name, cat scratch fever always causes a high fever. While fever can be a symptom, not everyone with the disease develops a fever. The name is partly a misnomer.

In summary, cat scratch disease is not a viral illness, cannot be passed between humans, and does not always involve a literal fever. Knowing the facts about this bacterial infection can help prevent misconceptions.


The Causative Agent

Cat scratch disease is not caused by a virus, but rather by a bacterium called Bartonella henselae. This bacterium is carried by cats, especially kittens, and can be transmitted to humans through scratches, bites, or even just contact with a cat’s saliva. According to the CDC, around 12,000 cases of cat scratch disease caused by B. henselae are reported annually in the United States.

The Bartonella henselae bacterium is a small, gram-negative rod. Cats are the main reservoir for this bacteria, with kittens being more likely to carry it than adult cats. The bacteria reside in the blood stream of cats and can be found in their saliva as well. When a cat scratches or bites a person, the bacteria can be introduced into the wound and cause an infection in humans.

While cat scratch disease is often benign, B. henselae can cause more serious complications in immunocompromised individuals. Fortunately, many healthy people’s immune systems can effectively fight the infection. But antibiotics are often prescribed for those with weaker immune systems to clear the bacteria.

So in summary, cat scratch disease is not caused by a virus but rather by a bacterium called Bartonella henselae that is carried by cats. Proper diagnosis and treatment of this bacterial infection is important, especially for those with weakened immune systems.





In summary, cat scratch disease is not caused by a virus, but rather by a bacterium called Bartonella henselae. This bacterium is carried by cats, particularly kittens, and can be transmitted to humans through bites, scratches, or even just contact with a cat’s saliva. The most common symptoms are swollen lymph nodes, fever, headache, fatigue, and a blister or pustule at the initial scratch site. While usually mild, complications like encephalitis, neuroretinitis, and osteomyelitis can occur. Diagnosis involves clinical examination, lab tests, and sometimes biopsy of affected tissue. Treatment is usually symptomatic, with antibiotics only used for severe cases. To prevent cat scratch disease, prompt cleaning and disinfecting of any cat wound is essential. While many may refer to it casually as cat scratch fever, it is important to understand that this illness is not caused by a virus at all, but rather by a bacterial infection.

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