What Is Sleeping Sickness? The Basics

Sleeping sickness is a serious parasitic infection spread by the bite of the tsetse fly. It is officially called human African trypanosomiasis, and it only occurs in sub-Saharan Africa. If left untreated, the parasite travels to the brain and causes severe neurological symptoms, which is where the name “sleeping sickness” comes from.

What Is Sleeping Sickness?

Sleeping sickness is caused by a single-celled parasite called Trypanosoma brucei. The parasite lives in the blood and tissue fluids of infected people and animals. When a tsetse fly bites an infected person, the fly picks up the parasite. The fly then passes the parasite to the next person it bites.

There are two forms of the disease. The two forms are caused by different subspecies of the parasite and are found in different regions of Africa. The form common in West and Central Africa tends to progress slowly over months or even years. The form found in East and Southern Africa is more aggressive and can progress to severe symptoms in a matter of weeks.

The disease is not spread from person to person through casual contact. You cannot catch it by touching someone, sharing food, or through sexual contact. The tsetse fly is the only natural way the infection passes to humans.

What Are the First Symptoms of Sleeping Sickness?

The first symptoms appear days to weeks after the bite. A painful red sore may develop at the site of the bite. This is called a chancre, and it is the first clear sign of infection in many people.

As the parasite multiplies in the blood, flu-like symptoms begin. Common early symptoms include:

• Fever that comes and goes
• Severe headaches
• Joint and muscle pain
• Swollen lymph nodes
• Itching
• Fatigue

A distinctive sign in some people is a swelling on the back of the neck. This happens when lymph nodes in that area become enlarged. Not everyone gets this symptom, but when it appears, it strongly suggests sleeping sickness.

How Does Sleeping Sickness Affect the Brain?

The disease has two stages. In the first stage, the parasite stays in the blood and lymph system. In the second stage, the parasite crosses the blood-brain barrier and enters the central nervous system. This second stage is when the classic sleep symptoms begin.

The name “sleeping sickness” comes from the disruption of the sleep-wake cycle. People do not simply sleep all day. Instead, their sleep pattern becomes severely fragmented. They may fall asleep suddenly during the day, but then struggle to sleep at night. This is a disturbance of the body’s internal clock, not ordinary tiredness.

Other neurological symptoms appear as the infection progresses. These can include confusion, personality changes, poor coordination, tremors, and difficulty walking. Without treatment, the neurological damage becomes severe and the disease is fatal.

How Is Sleeping Sickness Diagnosed?

Diagnosis requires a blood test, but the blood test alone is not enough. The parasite must be seen under a microscope to confirm the infection. In the second stage, doctors also examine spinal fluid. A lumbar puncture, sometimes called a spinal tap, is needed to check whether the parasite has reached the central nervous system.

Determining the stage of the disease is essential. The treatment for the first stage is different from the treatment for the second stage. Some medications used for the second stage are more toxic and must be given in a hospital setting. Giving the wrong medication for the stage of disease can be dangerous.

People who live in or travel to rural areas of sub-Saharan Africa where tsetse flies are common are at higher risk. Travelers who visit game parks and rural regions are the most likely to be exposed. The risk to short-term visitors is generally low, but it is not zero.

What Treatments Are Available?

Sleeping sickness is treatable, and treatment is highly effective when started early. The choice of medication depends on the stage of the disease and the subspecies of the parasite causing the infection.

For the first stage, the medications are generally well tolerated. For the second stage, the drugs must cross the blood-brain barrier to reach the parasite in the nervous system. These drugs are stronger and require close medical monitoring.

One important development is the oral medication fexinidazole. It was approved for use in several African countries for both stages of the disease caused by the West African subspecies. This is a significant improvement because older second-stage treatments required injections or intravenous infusions in a hospital. An oral option makes treatment far more accessible in rural areas.

Treatment must be guided by a doctor experienced with the disease. This is not a condition that can be managed with home remedies or over-the-counter medications. Anyone who suspects exposure should seek medical care immediately.

Can Sleeping Sickness Be Prevented?

There is no vaccine for sleeping sickness. Prevention focuses on avoiding tsetse fly bites and controlling the fly population in affected areas.

For travelers, practical measures are the main protection. Tsetse flies are attracted to bright colors, especially blue, and to the movement of vehicles. Wearing neutral-colored clothing that covers the arms and legs reduces bite risk. Using insect repellent provides some protection, though tsetse flies are less deterred by repellents than mosquitoes are.

Public health efforts in affected countries have been highly effective. Active screening programs identify infected people early, treat them, and reduce the number of people who can pass the parasite to flies. These programs have dramatically reduced the number of new cases reported each year.

Screening is especially important because people can be infected for months without obvious symptoms. In the West African form, a person may feel relatively well for a long period before neurological symptoms become apparent. Early detection through screening prevents both severe disease and further spread.

How Common Is Sleeping Sickness Today?

Sleeping sickness is now rare compared to historical levels. Major epidemics occurred in the 20th century, particularly in the 1920s and again in the 1990s and early 2000s. Since then, sustained control efforts have brought case numbers down dramatically.

In recent years, fewer than 1,000 cases have been reported annually across all affected countries. This is a major public health success. However, the disease has not been eliminated. Cases still occur in rural areas of countries like the Democratic Republic of the Congo, which reports the majority of cases.

The World Health Organization has set a target to eliminate sleeping sickness as a public health problem. This goal is realistic given current trends, but continued surveillance is necessary. If screening programs stop, the disease can return, as it has in past decades.

What Is the Outlook for Someone With Sleeping Sickness?

The outlook depends almost entirely on how early treatment begins. When the disease is caught in the first stage, treatment is highly effective and recovery is usually complete. Most people return to normal health without lasting problems.

When the disease reaches the second stage, treatment is still possible, but the outcome is more serious. The drugs are harder on the body, and some people may have lasting neurological damage even after the infection is cured. Some survivors report persistent fatigue, difficulty concentrating, or movement problems.

Without treatment, the disease is fatal. This is why prompt diagnosis is so important. Anyone who has traveled to a tsetse fly area and develops fever, headache, or unusual sleepiness should mention that travel history to a doctor. The travel history is the clue that leads to the correct test.

Who Is Most at Risk of Getting Sleeping Sickness?

The people most at risk are those who live in rural parts of sub-Saharan Africa where the tsetse fly is found. Farmers, fishermen, hunters, and people who work outdoors in these areas have the highest exposure. The flies live in vegetation along rivers and in forests, so people who spend time near these habitats are at greater risk.

Travelers are at much lower risk overall. Most travelers to Africa do not visit the specific rural areas where the fly lives. However, travelers on safari in game parks in affected countries can be exposed. The risk is highest for those who spend extended time in rural areas or who take part in outdoor activities near rivers and woodlands.

It is worth noting that sleeping sickness is not a risk in most of Africa. Major cities, coastal areas, and highland regions are generally free of the tsetse fly. The disease has a very specific geographic range, and most visitors to the continent will never be in a risk area.