Feeding on a human who carries the bacterium infects the louse. R. prowazekii grows in the louse's gut and is excreted in its feces. The louse transmits the disease by biting an uninfected human, who scratches the louse bite (which itches) and rubs the feces into the wound. The incubation period is one to two weeks. R. prowazekii can remain viable and virulent in the dried louse feces for many days. Typhus will eventually kill the louse, though the disease will remain viable for many weeks in the dead louse.<unk>  has historically occurred during times of war and deprivation. For example, typhus killed millions of prisoners in German Nazi concentration camps during World War II. The unhygenic conditions deliberately created by the Nazis in camps such as Auschwitz, Theresienstadt, and Bergen-Belsen allowed diseases such as typhus to flourish. Situations in the twenty-first century with potential for a typhus<unk>  would include refugee camps during a major famine or natural disaster. In the periods between outbreaks, when human to human transmission occurs less often, the flying squirrel serves as a zoonotic reservoir for the Rickettsia prowazekii bacterium. In 1916, Henrique da Rocha Lima proved that the bacterium Rickettsia prowazekii was the agent responsible for typhus; he named it after H. T. Ricketts and Stanislaus von Prowazek, two zoologists who had died from typhus while investigating<unk> s. Once these crucial facts were recognized, Rudolf Weigl in 1930 was able to fashion a practical and effective vaccine production method. He ground up the insides of infected lice that had been drinking blood. It was, however, very dangerous to produce, and carried a high likelihood of infection to those who were working on it. A safer mass-production-ready method using egg yolks was developed by Herald R. Cox in 1938. This vaccine was widely available and used extensively by 1943.
Epidemic typhus
Flying squirrel typhus
Murine typhus
Scrub typhus
Tomato fever
Haverhill fever
Blackwater fever
North Asian tick typhus