Overview
Sleeping sickness, known medically as human African trypanosomiasis, is caused by parasites passed on through the bite of an infected tsetse fly. It occurs only in parts of sub-Saharan Africa.
It begins with fever, headaches and swollen glands. Left untreated the parasites reach the brain, disturbing sleep, behaviour and coordination, and the illness is then almost always fatal. Treatment has improved greatly: an oral medicine now treats both stages of the disease.
Disease Summary
- Category
- Infectious Disease
- Cause
- Trypanosoma brucei parasites
- Transmission
- Bite of an infected tsetse fly
- Body System
- Nervous System
- Preventable
- Yes
- Curable
- Yes
Symptoms
Common Symptoms
The illness has two stages. The first affects the blood and lymph glands, the second the brain. The symptoms below belong mostly to the first stage.
A Sore Where the Fly Bit
CDC describes a raised red sore appearing 2 to 14 days after the bite. It is more common with the East African form and is not always noticed.
Bouts of Fever
Fever that comes and goes is listed by WHO among the features of the first stage.
Headache
Listed by both WHO and CDC among the first-stage symptoms.
Swollen Lymph Glands
Enlarged glands, particularly at the back of the neck, are characteristic of the West African form.
Joint and Muscle Pain
Listed by both WHO and CDC among the first-stage symptoms.
Itching and Irritated Skin
WHO lists itching and CDC lists itchy, irritated skin among the symptoms.
Weakness, Loss of Appetite and Weight Loss
CDC lists all three, and they often develop over weeks.
Disturbed Sleep
WHO calls sleep cycle disturbance a prominent feature of the second stage. CDC describes sleepiness during the day and wakefulness at night.
Danger Signs
Seek urgent medical attention immediately if any of the following symptoms develop.
Confusion or a Change in Behaviour
WHO lists behaviour changes and confusion among second-stage features. This is the stage that kills.
Reversed Sleep and Wake Pattern
Sleeping by day and lying awake at night is the feature that gives the illness its name and signals brain involvement.
Tremors, Unsteadiness or Slurred Speech
CDC lists these among the second-stage symptoms.
Seizures or Reduced Consciousness
Both are listed by CDC among second-stage symptoms and are emergencies.
Unusual Anxiety, Hallucinations or Delirium
CDC lists these among the second-stage symptoms. They are caused by the infection, not by a separate mental illness.
Fever After Being in a Tsetse Area
CDC advises telling a health worker about recent travel when unwell with fever, because the East African form progresses very quickly.
Diagnosis
Exposure and Travel History
CDC identifies hunters, villagers with infected cattle, and people working in or visiting game parks as at higher risk, while travellers to urban areas are at low risk.
Ruling Out Malaria First
In practice sleeping sickness is often found on a blood film taken to test for malaria, because the two share the same early symptoms.
Screening Tests in At-Risk Communities
WHO describes screening with a blood test, available for the West African form only, alongside clinical examination.
Finding the Parasite
WHO’s second step is confirmation by seeing the parasite under a microscope in blood or other body fluid. This is what makes the diagnosis.
Staging With a Lumbar Puncture
WHO’s third step is deciding the stage, which historically required examining spinal fluid. The newer oral treatment removes the need for this in most cases.
Laboratory Tests
Malaria Test
Done first in any fever in an endemic area. Sleeping sickness parasites are sometimes spotted on the same blood film.
Blood Film Microscopy
The parasites are seen moving in a fresh preparation and identified on a stained film. They are found more readily in the East African form.
Concentration Techniques
Spinning the blood to concentrate the parasites raises the chance of finding them, which matters in the West African form where numbers are low.
Lymph Node or Sore Fluid Sample
For the West African form, CDC states that confirmation often rests on examining fluid from a swollen gland or the bite sore.
Spinal Fluid Examination
Decides whether the parasites have reached the brain, by counting cells and looking for parasites in the fluid.
Treatment
Fexinidazole
WHO’s 2024 guidelines make this oral medicine a first-line option for both forms of the disease and for both stages. It removes the need for a lumbar puncture in most cases, which is a substantial practical advance.
Pentamidine
Used for the first stage of the West African form.
Suramin
Used for the first stage of the East African form.
Combination Therapy for Advanced West African Disease
A combination of nifurtimox and eflornithine is used for second-stage West African disease where fexinidazole is not suitable.
Follow-Up for Two Years
CDC states that follow-up continues for two years after treatment, with examination of spinal fluid every six months or sooner if symptoms return, because relapse must be caught.
Prevention
Know that there is no vaccine or preventive medicine
CDC states plainly that there is no vaccine or drug that prevents sleeping sickness. Prevention is avoiding bites.
Wear neutral-coloured, medium-weight clothing
CDC advises neutral colours, because tsetse flies are attracted to bright and very dark colours, and medium-weight fabric, because flies bite through thin cloth.
Check vehicles before getting in
CDC advises inspecting vehicles for tsetse flies before entering, because the flies are attracted to moving vehicles.
Avoid disturbing bushes
CDC notes the fly rests in bushes during the hottest part of the day but will bite if disturbed.
Use repellent, with realistic expectations
CDC states that repellents and treated clothing are not particularly effective against tsetse flies, though they prevent other insect bites that cause illness.
Find and treat cases in the community
WHO describes case detection followed by treatment as the way to both save the patient and break the cycle of transmission, complemented by control of the fly.
Risk Factors
Rural Communities in Endemic Africa
WHO reports that the population at risk is around 55 million people, with about three million at moderate to high risk.
- Communities in the Democratic Republic of the Congo, which reports the majority of cases
- Remote rural areas with limited access to health services
- Areas affected by displacement, conflict and poverty
- Villages near the river and woodland habitats where tsetse flies live
People With Heavy Outdoor Exposure
CDC names occupations and activities that bring people into tsetse habitat.
- Hunters and people working in woodland
- Farmers and herders, particularly where cattle are infected
- People fetching water or firewood along streams
- Anyone spending long periods in bush or savannah
Travellers and Game Park Workers
CDC identifies this group for the East African form specifically.
- Tourists visiting game parks
- People working in wildlife areas
- CDC notes that travellers to urban areas are at low risk
- The East African form progresses within one to several weeks of exposure
Rarer Routes of Infection
WHO and CDC name several uncommon but real routes.
- Unborn babies, since the parasite can cross the placenta
- Laboratory workers after a needlestick injury
- Recipients of blood transfusion or transplanted organs
- These routes are rare but they are documented
Complications
Invasion of the Brain
WHO describes behaviour changes, confusion, sensory disturbance and poor coordination in the second stage, with disturbed sleep as a prominent feature.
Seizures and Coma
Both are listed by CDC among the second-stage symptoms.
Multiple Organ Failure
CDC has reported rapid progression to organ failure requiring dialysis and breathing support in a severe case of the East African form.
Death
CDC states that a person can die within months of reaching the second stage, and that approximately 90% of cases are fatal without treatment.
Side Effects of the Older Medicines
WHO notes that the older treatment for advanced East African disease carried a fatality rate above 8% from serious adverse reactions. This is why the oral alternative matters.
Relapse After Treatment
CDC requires monitoring for two years after treatment, with spinal fluid examination every six months or sooner if symptoms return.
When to Seek Medical Care
Fever After Being in a Tsetse Area
CDC advises telling a health worker about recent travel when unwell with fever.
A Red Sore Where a Fly Bit You
CDC states the sore appears 2 to 14 days after the bite and is more common with the East African form.
Any Change in Sleep, Behaviour, Speech or Coordination
These indicate the second stage, which is the stage that kills.
Immediately, in East and Southern Africa
CDC states the East African form progresses in severity within one to several weeks of exposure, and WHO states it is fatal within weeks without treatment.
For Two Full Years of Follow-Up After Treatment
CDC states that follow-up continues for two years so that relapse is caught early.
Prognosis
Untreated, It Is Almost Always Fatal
CDC reports that approximately 90% of cases are fatal without treatment. WHO states the East African form is fatal within weeks without treatment.
Treatment Is Now Safer and Simpler
WHO’s recommendation of an oral medicine for both forms and both stages replaced treatments that were difficult to give and, in one case, carried a high fatality rate of its own.
Case Numbers Are at a Historic Low
WHO reports a 97% reduction in new cases over the past two decades, with fewer than 1 000 cases a year.
Follow-Up Matters
Relapse is possible, which is why CDC advises two years of monitoring after treatment.
Differential Diagnosis
Malaria
The most important alternative, sharing fever, headache and body aches. It must be tested for in every case, and the sleeping sickness parasite is often first spotted on the malaria film.
Typhoid Fever
Causes prolonged fever and malaise, and is separated by blood culture.
Bacterial or Tuberculous Meningitis
Also causes headache, confusion and abnormal spinal fluid, and is separated by examining that fluid.
HIV With a Brain Infection
Can produce confusion and behaviour change, and is separated by HIV testing and specific investigations.
Lymphoma and Other Causes of Swollen Glands
Cause persistent gland swelling without the parasite being found.
References
World Health Organization: Trypanosomiasis, human African (sleeping sickness)
WHO fact sheet on the parasite, the two forms, stages, diagnosis and treatment.
World Health Organization: Guidelines for the treatment of human African trypanosomiasis
WHO treatment guidelines, including the extension of oral fexinidazole to the East African form.
CDC: Clinical Guidance for Human African Trypanosomiasis
Staging criteria, treatment by form and stage, and follow-up requirements.
CDC: DPDx, African Trypanosomiasis
Laboratory diagnosis, specimen types and the tests used to find the parasite.
Frequently Asked Questions
How is sleeping sickness caught?
Through the bite of an infected tsetse fly, which is found only in parts of sub-Saharan Africa. CDC notes that risk rises with the number of bites, because most flies are not infected. Rarer routes include transmission from mother to unborn baby, needlestick injuries in laboratories, and blood transfusion.
Is there a vaccine or a preventive tablet?
No. CDC states plainly that there is no vaccine or drug that prevents sleeping sickness. Prevention is avoiding bites through neutral-coloured medium-weight clothing, checking vehicles, and not disturbing bushes where flies rest.
Can it be cured?
Yes. WHO’s 2024 guidelines make an oral medicine, fexinidazole, a first-line option for both forms of the disease and both stages. CDC advises follow-up for two years afterwards to confirm the cure and catch any relapse.
Why is it called sleeping sickness?
Because of what happens in the second stage, when the parasites reach the brain. WHO describes disturbance of the sleep cycle as a prominent feature, and CDC describes sleepiness during the day with wakefulness at night.
How quickly does it become serious?
It depends on the form. The West African form develops slowly over months or years. The East African form is much faster: CDC states it progresses in severity within one to several weeks of exposure, and WHO states it is fatal within weeks without treatment.