Typhus
Overview
Several different illnesses are called "typhus," all of them caused by one of the bacteria in the family Rickettsiae. Each illness occurs when the bacteria is passed to a human through contact with an infected insect.
Symptoms
The main symptoms include fever, headache, muscle aches and pains, cough, abdominal pain, nausea and vomiting, and diarrhea. Some patients experience only these symptoms. Some patients develop a rash, which can be flat or bumpy. The individual spots eventually develop crusty black scabs. Other patients go on to develop a more serious disease, in which encephalitis, pneumonia, and swelling of the liver and spleen (hepatosplenomegaly) occur.
Causes
The four types of typhus cause similar types of illnesses, though varying in severity. Epidemic typhus causes fever, headache, weakness, and muscle aches. It also causes a rash composed of both spots and bumps. The rash starts on the back, chest, and abdomen, then spreads to the arms and legs. The worst types of complications involve swelling in the heart muscle or brain (encephalitis). Without treatment, this type of typhus can be fatal. Brill-Zinsser disease is quite mild, resulting in about a week-long fever, and a light rash similar to that of the original illness. Endemic typhus causes about 12 days of high fever, with chills and headache. A light rash may occur.
Prevention
Prevention for each of these forms of typhus includes avoidance of the insects that carry the causative bacteria. Other preventive measures include good hygiene and the use of insect repellents.
Diagnosis
A number of tests exist that can determine the reactions of a patient's antibodies (immune cells in the blood) to the presence of certain viral and bacterial markers. When the antibodies react in a particular way, it suggests the presence of a rickettsial infection. Many tests require a fair amount of time for processing, so practitioners will frequently begin treatment without completing tests, simply on the basis of a patient's symptoms.
Prognosis
The prognosis depends on what types of complications an individual patient experiences. While children usually recover well from epidemic typhus, older adults may have as much as a 60% death rate without treatment. Brill-Zinsser, on the other hand, carries no threat of death. People usually recover uneventfully from endemic typhus, although the elderly, those with other medical problems, or people mistakenly treated with sulfa drugs may have a 1% death rate from the illness. Scrub typhus responds well to appropriate treatment, but untreated patients have a death rate of about 7%. The relatively high death rate from untreated typhus is one reason why some researchers are concerned that its causative organisms might be used in the future as agents of bioterrorism.
Treatment
The antibiotics tetracycline or chloramphenicol are used for treatment of each of the forms of typhus.