Cat scratch fever is absolutely real. It’s a bacterial infection caused by Bartonella henselae, and it’s one of the most common infections people pick up from domestic animals. An estimated 6.4 cases per 100,000 people occur annually in southern U.S. states, with children ages 5 to 9 at the highest risk. The name sounds like a rock song (because it is one), but the condition itself can range from a mild nuisance to a serious illness.
How You Get It
The infection starts with fleas. Cats pick up the Bartonella henselae bacteria from infected fleas, and the bacteria then circulate in the cat’s bloodstream. When an infected cat scratches or bites you, the bacteria enter through the break in your skin. Cats don’t have to look sick to carry the infection, and kittens are more likely to transmit it than adult cats because they tend to scratch and bite more during play.
You can’t catch it from another person. The chain is always flea to cat to human. Cases peak in late summer and fall, when flea populations are at their highest, with a second smaller spike in January.
What It Looks and Feels Like
Within a few days of a scratch or bite, the wound becomes red and swollen instead of healing normally. A small blister or pus-filled bump often forms at the site. This is the first real sign that something beyond a normal scratch is happening.
One to three weeks later, lymph nodes near the wound swell up and become tender. The location depends on where you were scratched: a scratch on your hand or arm typically causes swelling in your armpit, while a scratch on your leg leads to swollen glands in your groin. The swollen nodes can become quite large and painful.
Many people also develop flu-like symptoms: headache, fatigue, joint pain, fever, and loss of appetite. For most healthy people, these symptoms resolve on their own over several weeks to a couple of months without any treatment. The infection is self-limiting in the vast majority of cases.
When It Gets Serious
In a small percentage of cases, the infection doesn’t stay confined to the lymph nodes. It can spread to the eyes, liver, spleen, bones, or brain. One specific eye-related complication called Parinaud oculoglandular syndrome, which involves inflammation of the membrane lining the eye along with swelling of nearby lymph nodes, shows up in about 2 to 7 percent of cases. Another eye complication, neuroretinitis, causes swelling of the optic nerve and a distinctive star-shaped pattern of inflammation in the retina that can temporarily affect vision.
More rarely, the bacteria can cause inflammation of the heart valves (endocarditis), bone infections, or encephalitis. People with weakened immune systems face the greatest risk for these severe complications, though they’ve also been documented in otherwise healthy individuals. For immunocompromised patients, the infection can be genuinely dangerous and even life-threatening.
How It’s Diagnosed
Doctors often suspect cat scratch disease based on the combination of a recent cat scratch, a wound that won’t heal, and swollen lymph nodes. To confirm it, they typically order a blood test that checks for antibodies your immune system produces in response to the bacteria. A high level of these antibodies strongly suggests an active or recent infection.
In cases where the diagnosis is uncertain, or when the infection has spread to organs like the heart, a more precise DNA-based test (PCR) can detect the bacteria directly in blood or tissue samples. This test is especially useful for identifying the exact species of Bartonella involved.
Treatment
Most healthy people don’t need antibiotics. The swollen lymph nodes gradually shrink, and the infection clears on its own. Warm compresses and over-the-counter pain relievers can help manage discomfort in the meantime.
When the infection is more severe, or in people with compromised immune systems, doctors prescribe antibiotics. The course typically lasts several weeks, and for immunocompromised patients, treatment may continue for three months or longer to prevent the infection from coming back. In rare cases involving heart valve infections, treatment can extend well beyond that and may require a combination of antibiotics.
Reducing Your Risk
Flea control is the single most effective prevention strategy. Keeping your cat on a regular flea prevention product breaks the transmission chain at its source. No vaccine exists for cats against this bacteria, so flea management is the primary tool.
Beyond flea control, a few simple habits make a difference. Wash cat scratches and bites promptly with soap and running water. Avoid rough play with cats, especially kittens, that could lead to scratches. Keeping cats indoors reduces their exposure to fleas and to feral cats that may carry the bacteria. If you’re immunocompromised, these precautions are especially worth taking seriously, since you’re the group most vulnerable to the infection’s worst outcomes.