of the Burundian Civil War in 1993, which caused the displacement of 760,000 people. Refugee camps were crowded and unsanitary, and often far from towns and medical services. 21st century A 2005 study found seroprevalence of R. prowazekii antibodies in homeless populations in two shelters in Marseille, France. The study noted the "hallmarks of epidemic typhus and relapsing fever". History of vaccines Major developments for typhus vaccines started during World War I, as typhus caused high mortality, and threatened the health and readiness for soldiers on the battlefield. Vaccines for typhus, like other vaccines of the time, were classified as either living or killed vaccines. Live vaccines were typically an injection of live agent, and killed vaccines are live cultures of an agent that are chemically inactivated prior to use. Attempts to create a living vaccine of classical, louse-borne, typhus were attempted by French researchers but these proved unsuccessful. Researchers turned to murine typhus to develop a live vaccine. At the time, murine vaccine was viewed as a less severe alternative to classical typhus. Four versions of a live vaccine cultivated from murine typhus were tested, on a large scale, in 1934. While the French were making advancements with live vaccines, other European countries were working to develop killed vaccines. During World War II, there were three kinds of potentially useful killed vaccines. All three killed vaccines relied on the cultivation of Rickettsia prowazekii, the organism responsible for typhus. The first attempt at a killed vaccine was developed by Germany, using the Rickettsia prowazekii found in louse feces. The vaccine was tested extensively in Poland between the two world wars and used by the Germans for their troops during their attacks on the Soviet Union. A second method of growing Rickettsia prowazekii was discovered using the yolk sac of chick embryos. Germans tried several times to use this technique of growing Rickettsia prowazekii but no effort was pushed very far. The last technique was an extended development of the previously known method of growing murine typhus in rodents. It was discovered that rabbits could be infected, by a similar process, and contract classical typhus instead of murine typhus. Again, while proven to produce suitable Rickettsia prowazekii for vaccine development, this method was not used to produce wartime vaccines. During WWII, the two major vaccines available were the killed vaccine grown in lice and the live vaccine from France. Neither was