Typhus fever – infectious disease

Typhus, also known as typhus fever is a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus. Common symptoms include fever, headache, and a rash.[1] Typically these begin one to two weeks after exposure.[2]

They are caused by a bacterial infection. Epidemic typhus is due to Rickettsia prowazekii spread by body lice, scrub typhus is due to Orientia tsutsugamushi spread by chiggers, and murine typhus is due to Rickettsia typhi spread by fleas.[1]

There is no commercially available vaccine. Prevention is by reducing exposure to the organisms that spreads the disease.[3][4][5] Treatment is with the antibiotic doxycycline.[2] Epidemic typhus generally occurs in outbreaks when poor sanitary conditions and crowding are present.[6] While once common, it is now rare.[3] Scrub typhus occurs in Southeast Asia, Japan, and northern Australia.[5] Murine typhus occurs in tropical and subtropical areas of the world.[4]

Typhus has been described since at least 1528. The name comes from the Greek typhus (τύφος) meaning hazy, describing the state of mind of those infected.[7] While “typhoid” means “typhus-like”, typhus and typhoid fever are distinct diseases caused by different types of bacteria.[8]

Signs and symptoms[edit]

The following signs and symptoms refer to epidemic typhus as it is the most important of the typhus group of diseases.[9]

Signs and symptoms begin with sudden onset of fever, chills, headache, and other flu-like symptoms about 1 to 2 weeks after being infected.[10] Five to nine days after the symptoms have started, a rash typically begins on the trunk and spreads to the extremities. This rash eventually spreads over most of the body, sparing the face, palms, and soles. Signs of meningoencephalitis begin with the rash and continue into the second or third weeks. Other signs of meningoencephalitis include sensitivity to light (photophobia), altered mental status (delirium), or coma. Untreated cases are often fatal.

Causes[edit]

Multiple diseases include the word “typhus” in their description.[11] Types include:

Condition Bacterium Reservoir/vector Notes
Epidemic Louse-borne Typhus Fever Rickettsia prowazekii Human Body louse When the term “typhus” is used without clarification, this is usually the condition described. Historical references to “typhus” are now generally considered to be this condition.
Murine typhus or “endemic typhus” Rickettsia typhi Fleas on rats
Scrub typhus Orientia tsutsugamushi Harvest mites on humans or rodents Unlike the two conditions above, though it has the word “typhus” in the name, it is currently usually not classified in the typhus group, but in the closely related spotted fever group.[12]
Queensland tick typhus[13] or “Australian tick typhus” (and a spotted fever[14]) Rickettsia australis Ticks

Prevention[edit]

As of 2017 there is no commercially available vaccine.[3][5][4] A vaccine has been in development for scrub typhus known as the scrub typhus vaccine.[15]

Treatment[edit]

The American Public Health Association recommends treatment based upon clinical findings and before culturing confirms the diagnosis.[16] Without treatment, death may occur in 10 to 60 percent of patients with epidemic typhus, with patients over age 60 having the highest risk of death.[citation needed] In the antibiotic era, death is uncommon if doxycycline is given. In one study of 60 hospitalized patients with epidemic typhus, no patient died when given doxycycline or chloramphenicol.[17] Some patients also may need oxygen and intravenous (IV) fluids.

Epidemiology[edit]

According to the World Health Organization, the current death rate from typhus is about one out of every 5,000,000 people per year.[18]

Only a few areas of epidemic typhus exist today. Since the late 20th century, cases have been reported in Burundi, Rwanda, Ethiopia, Algeria, and a few areas in South and Central America.[19][20][21][22]

Except for two cases, all instances of epidemic typhus in the United States have occurred east of the Mississippi River. An examination of a cluster of cases in Pennsylvania concluded the source of the infection was flying squirrels.[23] Sylvatic cycle (diseases transmitted from wild animals) epidemic typhus remains uncommon in the US. The Centers for Disease Control and Prevention have documented only 47 cases from 1976 to 2010.

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