Bartonellosis is an infectious disease caused by bacteria from the genus Bartonella. The most common form is cat scratch fever, which can occur after being scratched or bitten by a cat. Symptoms may include fever, fatigue, and swollen lymph nodes. The disease can also be associated with other conditions, such as Bartonella henselae infection, which can lead to more severe complications in individuals with weakened immune systems. Diagnosis typically involves blood tests, and treatment usually consists of antibiotics to help manage the infection.