Typhus should not be confused with typhoid fever. Although there are some similarities between these two febrile illnesses, they are caused by different bacteria and typhoid is transmitted mainly in infected food, not by body lice.Louse-borne typhus (also known as epidemic typhus) is similar in many ways to relapsing fever. Like RF, it is a bacterial infection transmitted by the human body louse, but the causative bacteria are different. They are extremely small bacteria called Rickettsia prowazekii (named after two doctors who died of typhus when they were researching into the disease). These bacteria quickly have to get inside the cells of their human host in order to survive and multiply – unlike the bacteria that cause RF, which circulate in the blood and don't live inside the host's body cells.
Louse-borne typhus has caused major epidemics over many centuries, resulting in millions of deaths during war, famine and mass displacement. The WHO estimates that globally in recent years around 1,400 people die from typhus every year. Like RF, outbreaks occur in situations of overcrowding in unhygienic conditions where body lice can easily breed and spread.