Cat scratch disease is a bacterial infection caused by the bacteria bartonella henselae, which is present in cat saliva. It is transmitted to humans through exposure to cat saliva, primarily by being licked, bitten, or scratched by a cat. Most people who suffer from cat scratch disease do not remember a cat bite or scratch, so neither is actually necessary to develop the condition. It is not a particularly dangerous condition, but if the person is very young, old, or is suffering from an impaired immune system, medical supervision may be recommended. The symptoms discussed below will generally form a week or two after the infection sets in.