Flea-borne typhus is a disease caused by Rickettsia typhi bacteria that are spread by fleas. Human cases of flea-borne typhus are reported worldwide, but mainly in tropical and coastal areas. In the United States, most cases occur in Texas, California, and Hawaii, with an average of about 300 cases every year. In California, flea-borne typhus is considered endemic (always present) in areas of Los Angeles and Orange counties, but cases sometimes are also reported from other parts of California. A person can get typhus by coming in contact with fleas that are infected with the bacteria that cause typhus. Fleas become infected when they bite small animals like rats, opossums, and stray cats. Fleas can then spread the bacteria that cause typhus to other animals and humans.