Cat scratch fever (cat scratch disease) is not contagious from person to person. You cannot catch it from someone who has it, and an infected person poses no risk to family members, coworkers, or anyone else. The bacteria responsible, Bartonella henselae, spreads to humans only through the scratch or bite of an infected cat, or when an infected cat licks an open wound.
How Cat Scratch Fever Actually Spreads
The chain of transmission starts with fleas, not cats themselves. Fleas carry Bartonella henselae and pass it to cats through their bites. Infected flea droppings (often called “flea dirt”) collect on a cat’s claws and fur. When a cat scratches or bites you, the bacteria enter through the break in your skin. A cat licking an open wound or your eyes can also transmit the infection.
Cats themselves often show no symptoms. Kittens are more likely to carry the bacteria than adult cats, partly because they’re more prone to flea infestations and more likely to scratch during play. Both domestic and feral cats can be carriers.
Who Gets It Most Often
Children between ages 5 and 9 have the highest infection rate, at roughly 9.4 cases per 100,000 people per year in the United States. That likely reflects how kids play with cats: more roughhousing, more scratches, less careful wound cleaning. Cases are most common in the southern U.S., where warmer, more humid climates support larger flea populations. Rates are lowest in drier mountain regions, where fleas are less common.
People with weakened immune systems face greater risk of severe complications. In people with advanced HIV, for example, the infection can become chronic, lasting months to over a year, and can affect multiple organ systems.
Symptoms and Timeline
After a scratch or bite from an infected cat, symptoms typically develop within one to two weeks. In most cases, a small reddish-brown bump (about half a centimeter across) forms at the scratch site. This bump is often the first clue that something more than a simple scratch is going on.
Within 3 to 10 days of that bump appearing, nearby lymph nodes swell. If you were scratched on the hand, for instance, the lymph nodes in your armpit on that side would enlarge and become tender. You may also develop a low-grade fever, fatigue, headache, and a general feeling of being unwell. For most healthy people, the swollen lymph nodes are the most noticeable and bothersome symptom, sometimes persisting for weeks or even a few months before resolving on their own.
When It Becomes More Serious
In a small percentage of cases, the infection moves beyond the lymph nodes. Bartonella can cause eye inflammation (retinitis), heart valve infection (endocarditis), bone infection, and liver complications. These severe outcomes are rare in people with healthy immune systems but occur more frequently in immunocompromised individuals. Skin lesions that resemble other conditions can develop in advanced cases, making diagnosis tricky without lab testing.
How It’s Diagnosed
Diagnosis usually starts with your symptoms and a history of cat contact. Blood tests that look for antibodies against Bartonella are the most commonly used tool, but they aren’t perfect. The antibodies can cross-react with other bacteria, sometimes producing misleading results. Culturing the bacteria from blood or tissue is possible but has low sensitivity because Bartonella is slow and difficult to grow in a lab. Molecular testing (PCR) can identify the specific bacterial species and is particularly useful when standard tests come back negative but suspicion remains high.
Treatment
Most cases of cat scratch disease in healthy people resolve without antibiotics, though the process can take several weeks. When the infection is more severe, or when it occurs in someone with a compromised immune system, antibiotics shorten the illness and prevent complications. Treatment typically lasts at least three months for immunocompromised patients. Swollen lymph nodes that become very large and painful sometimes need to be drained, but this is uncommon.
Preventing Cat Scratch Fever
Since fleas are the root of the problem, flea control is the single most effective prevention strategy. Keep your cats on a veterinarian-recommended flea prevention product year-round. Permethrin-based products are safe for dogs but should never be used on cats. No vaccine exists for Bartonella in cats or dogs.
Beyond flea control, a few practical habits reduce your risk:
- Wash scratches and bites immediately with soap and running water
- Avoid rough play with cats, especially kittens, that might lead to scratches
- Don’t let cats lick open wounds or broken skin
- Keep cats indoors to limit their exposure to fleas and feral cats
Indoor cats with consistent flea prevention are unlikely to carry Bartonella. The risk is highest with outdoor cats, stray cats, and kittens from shelters or unknown environments where flea exposure is common.