Cat scratch disease is an infection transmitted from humans to cats. In most cases, the disease does not pose a serious health threat to the patient.

Cats infected with the bacteria Bartonella henselae transmit cat scratch disease to humans through scratches and bites. In other cases, people get cat scratch disease when they touch their own eye, or through broken skin after petting a cat that has the bacteria on its fur. The infection can also be transmitted in this way in people who have the cat’s saliva on their fingers. 

A bump or blister at the site of injury is the first sign of cat scratch disease. It may take anywhere from three to 10 days before this sore appears. About two to three weeks after infection, the patient will begin to experience swelling of the lymph nodes near the infection site.

In most cases, cat scratch disease resolves on its own and does not require treatment. However, more severe cases in which symptoms linger should receive medical attention. In addition, patients with compromised immune systems may be at greater risk for health problems as a result of cat scratch disease.

In diagnosing cat scratch disease, a physician will look for a characteristic scratch or injury and the presence of an enlarged spleen (splenomegaly). In addition, blood tests may be performed and samples of lymph fluid may be taken.