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. 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.