Epidemic typhus is an uncommon infection caused by the bacterium Rickettsia prowazekii and is also called louse-borne typhus [1][2]. It is transmitted to humans by the body louse Pediculus humanus corporis [2].
Disease overview
Bacterial Evidence-backed information EN 5/7 applicable sections · ZH 5/7 applicable sections Updated Oct 23, 2026
Epidemic typhus, also known as louse-borne typhus, is an uncommon bacterial infection caused by Rickettsia prowazekii that was historically responsible for millions of deaths but is now rare [1][2]. It persists as a public-health concern because poor sanitary conditions favor body-louse proliferation and because the agent is regarded as a potential bioterrorism threat [2]. Rare United States cases linked to flying squirrels have also been documented [1][3].
Read the full clinical and epidemiological profile 6
Symptoms typically begin within two weeks after contact with infected body lice [1]. Some individuals can remain asymptomatically infected for years and rarely experience a later relapse known as Brill-Zinsser disease, which presents with milder symptoms than the initial illness and is associated with a weakened immune system [1].
The disease is now rare but can occur where extreme overcrowding permits body lice to pass between people [1]. In the United States, rare cases termed sylvatic typhus have followed exposure to flying squirrels and their nests, with more than 20 squirrel-related acute cases reported [1][3]. No outbreak of epidemic typhus has yet been reported in central and southern Europe, though reemergence there is considered possible [4].
Humans acquire infection through contact with infected body lice, specifically Pediculus humanus corporis [1][2]. Since 1975, human infection in the USA has also been linked to contact with the flying squirrel Glaucomys volans [2][3]. Brill-Zinsser disease relapse is unrelated to louse infestation and instead reflects reactivation of a persistent infection [2].
No vaccine is available for epidemic typhus [1]. Reducing risk depends on preventing and controlling body-louse infestation, including access to bathing and clean clothing [1]. Public-health authorities emphasize that poor sanitary conditions conducive to louse proliferation must be addressed to limit threat [2].
- 1 US Centers for Disease Control and Prevention. About Epidemic Typhus | Typhus Fevers | CDC [Internet]. cited 23 Oct 2026. Available from: https://www.cdc.gov/typhus/about/epidemic.html
- 2 Bechah Y et al. Epidemic typhus. Lancet Infect Dis. 2008 Jul. PMID: 18582834. doi: 10.1016/S1473-3099(08)70150-6. PubMed: https://pubmed.ncbi.nlm.nih.gov/18582834/
- 3 Woodward TE et al. Murine and epidemic typhus rickettsiae: how close is their relationship? Yale J Biol Med. 1982 May-Aug. PMID: 6817526. PubMed: https://pubmed.ncbi.nlm.nih.gov/6817526/
- 4 Blanco JR et al. Rickettsiosis in Europe. Ann N Y Acad Sci. 2006 Oct. PMID: 17114677. doi: 10.1196/annals.1374.003. PubMed: https://pubmed.ncbi.nlm.nih.gov/17114677/
- A75.0
- 1C30
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