Bartonella is a group of bacteria that causes infectious diseases and are mainly transmitted by carriers such as fleas, lice, or sandflies. These carriers are also called vectors. One species of the Bartonella bacteria is the Bartonella henselae that causes a bacterial infection known as cat scratch fever or cat scratch disease. The name was derived from the main cause of contracting Bartonella henselae infection which are cats. Bartonella henselae infects cats through infected fleas. The infected cats may transmit the bacteria to humans through bites and scratches. It can also be transmitted when the infected cat licks an open wound or its saliva gets on the surface of the whites of the eyes. Cat owners are the number one at risk to have the cat scratch disease. Anyone can have it but it most commonly occurs in children between 5 and 9 years old. Males are most likely to be hospitalized even though females are the majority to be diagnosed with cat scratch disease. People with a weak immune system, pregnant women, and people with diseases such as cancer, diabetes, HIV/AIDS, and those who have undergone organ transplants are also at risk. Cat scratch disease increases the risk of becoming severely ill.
Cat scratch disease cases occur worldwide, but the incidence is greater in areas with higher temperatures and humidity since it supports heavy populations of fleas.