Cat scratch disease (CSD) is a bacterial infection that primarily affects the lymph nodes. It is typically caused by the bacteria bartonella (Bartonella henselae). It is usually transmitted by being scratched or bitten by a cat, but rarely, no scratch or bite is involved. Symptoms frequently include the formation of a small bump at the site of the scratch or bite, followed by fever and swollen lymph nodes (lymphadenopathy) within 1-3 weeks. Lymphadenopathy commonly resolves on its own within a few months, but in some cases it may persist for up to 2 years. People with weakened immune systems (and less commonly, people with healthy immune systems) may develop more widespread disease and additional symptoms or neurological complications, which can be severe. In most cases, particularly in children and adolescents, having CSD once means that it cannot occur again. The recurrence of symptoms months after disease onset has been reported in a few adults with CSD. Treatment in mild or moderate cases typically involves medicines or strategies to improve symptoms, such as using fever reducers, pain relievers, or local heat over the affected lymph node(s). In more severe or systemic cases, management may involve lymph node aspiration and/or antibiotics.

Most people with cat scratch disease have been bitten or scratched by a cat and develop a mild infection at the point of injury within about 3-14 days. The infected area may be warm and painful and may appear appear swollen and red with round, raised lesions. Lymph nodes, especially those around the head, neck, and upper limbs, become swollen. Additionally, a person with cat scratch disease may experience fever, headache, fatigue, achiness and discomfort (malaise), sore throat, enlarged spleen, and/or loss of appetite.