The CDC divides sleeping sickness into two different diseases. East African sleeping sickness is caused by Trypanosoma brucei rhodesiense , but West African sleeping sickness is caused by Trypanosoma brucei gambiense. Apart from this difference the diseases are very similar

Infection
When a tsetse fly infected with the protozoa that causes sleeping sickness bites a human the organism is transferred. The bite of a tsetse fly is easily noticable by the pain it causes, and the red swelling that may develop afterwards.

It is theoretically possible for the infection to be passed in bodily fluids, whether in a blood transplant, from a mother to her child or any other concievable way. Because death occurs fairly soon after infection this method of transmission is uncommon.

Symptoms
Symptoms may begin to occur from between 7-30 days of infection. The most common of these are:

If no treatment takes place, death typically occurs after several more weeks or months.

Treatment
Sleeping sickness must be caught early if the sufferer is to survive. Diagnosis is usually by lab examination of CS fluid. Treatment involves the use of drugs, the specific combination depending on which type of sleeping sickness is present. All of these drugs cause extensive and undesirable side-effects, but this is considered more desirable than the alternative of near certain death.

No vaccine exists for sleeping sickness, and immunity does not develop. Aside from staying out of Africa, the best way to avoid contracting sleeping sickness is the prevention of fly bites. This can be accommplished by wearing covering clothing, and sleeping in locations protected by netting. Tsetse flies tend to live in bushes, so not disturbing undergrowth is a sensible measure.

Cases of sleeping sickness have risen in central African countries since they gained independence. Due to poor recording of statistics regarding the disease it is difficult to accurately estimate how many cases there are per year. It is thought that as many as 20 000 people per year could die due to sleeping sickness.

Sources:
CDC
WHO
Collins Medical Encyclopaedia

At the beginning of the 20th century, an epidemic of sleeping sickness (or encephalitis lethargica) swept through Europe. The disease broke out in 1916. In 1917, Constantin von Economo (Romanian aristocrat of Macedonian extraction, doctor of psychiatry in Vienna, and Austria's first military pilot) undertook study of the phenomenon after returning to his clinic in the wake of his brother's death in The War.

In January of that year, von Economo began to delineate the common symptoms preceding the final descent into an often-fatal sleep: high temperature, hallucination, impaired vision, and excessive sleepiness.

Approximately a third of patients reporting precursor symptoms fell asleep for extended periods, and were impossible to wake. The majority of these died while still asleep. Others manifested a complete inability to fall asleep, even with the administration of strong sedatives. All of these patients died of extreme fatigue and related side-effects.

A small number of patients sank into a deep sleep from which they neither woke nor died, until neurophysiologst Oliver Sacks found them - years later - and woke them by administration of levodopa. (His book "The Awakenings" and the film of the same name chronicles the tribulations - and horrifying trials - of Dr. Sacks and his patients in this process.)

The disease spread throughout the world and killed more than five million people over the course of 10 years. In 1927 the epidemic disappeared with the same mysterious abruptness in which it appeared.

This form of encephalitis still provides scientists with a resilient mystery, as it can be caused by a variety of agents (virus, bacteria, or spirochete), and symptoms are often interpreted etiologically as sleep disorders rather than viral infection.

While incidence of sleeping sickness has tapered down to a rarity, it is still found occasionally. There is no known cure.

Source: The Enchanted World of Sleep, by Paretz Lavie

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