Cat scratch fever, also called cat scratch disease, is an infection most commonly caused by the bacterium Bartonella henselae. It can follow a cat scratch or bite and often presents with swollen lymph nodes near the exposure site (armpit, neck, groin). Fever, fatigue, and headache may occur. Most cases are self-limited and improve with supportive care, but complications—such as eye involvement or systemic disease—are more likely in immunocompromised people. When suspected, diagnosis is based on clinical history and may be supported by laboratory testing to rule out other causes.