Classical typhus fever occurs when infected body lice or their faeces contaminate a bite, an abrasion or the eyes. It can also be caused by inhalation of dried faeces. The disease can spread rapidly in times of famine and war when large numbers of people are living in crowded, unsanitary conditions. Incidence tends to increase in winter, when close quarters and heavy clothing contribute to infestation by body lice. The lice live in clothing and feed on human blood.
Symptoms of infection, which begin suddenly about 1 to 2 weeks after exposure, include high fever, severe headache, dry cough, chills, limb pain, nausea and vomiting. Typhus rash typically appears first on the torso then spreads over the body. Delirium and neurological symptoms may appear, and survivors may suffer permanent damage. If untreated, the disease may either resolve or result in death after about 2 weeks; the death rate if untreated is 30 percent.
The causative organism is Rickettsia prowazeki, (so-called after Ricketts and Prowazeki, investigators of typhus, both of who died of the disease.) The rickettsiae can survive in the dried faeces of lice for 60 days and this infected material is probably the main source of infection. There is evidence that squirrels also carry the disease organism.
Epidemic louse-borne typhus can be found in cool, mountainous regions of Africa, Central and South America, Asia, Eastern Europe. It is particularly common in eastern Europe, Russia, northern Africa and China. It manifests differently in different localities. The death rate without antibiotic treatment is variable, varying from nearly 100% in epidemics among debilitated refugees to about 10%.