Cat-scratch disease

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Cat-scratch disease is infection caused by the gram-negative bacteria Bartonella henselae and transmitted by a scratch or bite from an infected cat, often causing a crusted bump and swollen lymph nodes.

People with cat-scratch disease have a red bump at the site of the scratch, and some have a fever, headache, poor appetite, or swollen lymph nodes.
In people with a weakened immune system, the infection may spread throughout the body and, without treatment, may result in death.
Doctors do blood and fluid tests to check for the bacteria.
Usually, applying heat to the infected area and taking pain relievers are all that is needed, but if people have a weakened immune system, doctors give them antibiotics.

(See also Overview of Bacteria.)
Most domestic cats throughout the world are infected, but most show no signs of illness. Fleas transmit the Bartonella bacteria from one cat to another. People become infected by a cat bite or scratch, which need not be severe for infection to occur.