What Causes Typhus?

The causes of typhus, which shouldn't be confused with typhoid fever, are contact with bacteria that can be carried by lice, fleas, mites, or by animal hosts like rats. The most common types of the illness are called epidemic, endemic or murine, Queensland tick, and scrub. Each type represents contact with a different type of bacteria. All but one of these types, scrub typhus, are related to contact with forms of Rickettsia bacteria.

Specifically, murine or endemic typhus results from infection with Rickettsia typhi. Epidemic typhus occurs in people infected with Rickettsia prowazekii. Queensland tick is caused by Rickettsia australis. Rickettsia bacteria, as mentioned, do not cause the last type. Instead scrub typhus results from colonization by Orientia tsutsugamushi, and though it has features in common with the other illnesses, it may not be considered true variant of the disease.

Typhus is not common in the Western world because it ordinarily requires fairly poor living environments where pest infestation is tolerated. It most often shows up in the Western world in places notorious for poor living circumstances, like underfunded jails. It should also be noted that each type tends to be carried by specific animals. Rat fleas typically carry murine variants of the illness, mites or rodents may carry scrub typhus, ticks carry Queensland forms, and human lice are most commonly associated with the epidemic type of the disease. This is why incidence of these illnesses remains low in the Western world; most people with decent living quarters exert some effort to control pest populations.

There may be problems associated with this condition in especially poor or primitive living circumstances. The most profound outbreaks of typhus in the mid 1950s and onward have taken place in countries in Africa. Mass infections resulting from contact with Rickettsia prowazekii means that the disease has passed from person to person through human lice. Epidemic typhus can’t be communicated except through exposure to lice.

When these various illnesses were first described many centuries ago, some desperation was attached to their description. Depending on type, a typhus illness could have as much as a 60% mortality rate. Today, in areas where antibiotics are readily available, mortality rate is low. Many common antibiotics are capable of killing bacterial infections caused by Rikettsiae and Orientia, and understanding of how the disease is spread can help people eradicate it from their households with measures to control louse, flea, mite or vermin encroachment. In undeveloped countries, threat of epidemics of typhus are more real and more challenging because people may not have access to antibiotics to cure the disease.