Lassa fever: Viral infectious disease with fever and bleeding

Lassa fever is an acute infectious disease that mainly occurs in some African countries. The disease is transmitted by rats and causes a seriously toxic syndrome with fever, bleeding, shock and neurological symptoms. The disease can mainly be treated symptomatically and supportively, although effective medicine is available at an early stage of the disease. The complications of this condition can be very serious, even with a fatal course of the disease. Lassa fever was first documented in 1969 in the city of Lassa (Nigeria).

  • Epidemiology and risk factors Lassa fever
  • Causes of viral infectious disease: infected rats
  • Symptoms: Fever and bleeding
  • Initial stage
  • Later stage
  • Diagnosis and examinations
  • Treatment via medicine
  • Prognosis of disease
  • Complications

Epidemiology and risk factors Lassa fever

The contagious infectious disease can be found in West African countries, such as Benin, Ghana, Guinea, Liberia, Mali, Nigeria and Sierra Leone. The annual incidence is 100,000-300,000 patients, of which approximately 5,000 patients die annually. Lassa fever occurs in all age groups. Both men and women are affected by the infectious disease. Patients at greatest risk are residents of rural areas where the hosts (rodents) are usually found. The rodents prefer locations with poor sanitary facilities or overcrowded living conditions. Furthermore, healthcare workers are at high risk of contracting Lassa fever if they do not take adequate hygienic measures. For example, in November 2019, a Dutch tropical doctor who was employed in Sierra Leone died as a result of the disease.

Causes of viral infectious disease: infected rats

The Lassa virus is transmitted to humans through contact with contaminated food or household items, the urine, feces or saliva of rodents, which contain the virus. The host is in fact a rodent of the genus Mastomys, commonly known as the “many-nipped mouse”. Mastomys rats infected with the Lassa virus are not sick, but they do excrete the virus through urine, feces and saliva. The spread of the virus also occurs through direct contact with the blood, urine, feces or other body secretions of a patient infected with Lassa fever. If insufficient hygienic measures are in force in hospitals, infection with the Lassa virus is also more likely to occur, for example through the reuse of needles or contaminated equipment.

Symptoms: Fever and bleeding

On average, 80% of patients infected with the Lassa virus do not develop any symptoms. About 10-30% of infections are symptomatic. The incubation period (time between infection and the appearance of symptoms) is 6-21 days.

Initial stage

In the early stages, the disease is mainly characterized by the presence of general symptoms such as fever, general weakness and a general ill feeling (malaise). After a few days, the following symptoms are possible: headache, sore throat, swollen lymph nodes, muscle pain (myalgia), chest pain, nausea, vomiting, diarrhea, coughing, abdominal pain and (severe) back pain. A transient skin rash is also present in a number of patients.

Later stage

In severe cases, swelling of the face, fluid accumulation in the lungs (pulmonary edema), bleeding from the mouth, nose, ears, vagina or gastrointestinal tract and low blood pressure (hypotension) may occur. Lassa fever is therefore known as a viral hemorrhagic fever disease (“hemorrhage” is the medical term for bleeding). The fever usually lasts one to three weeks. Shock, convulsions (convulsions: uncontrollable physical movements and changes in consciousness), tremor (tremors), disorientation, confusion and coma are other serious symptoms that may appear in the later stages.

Diagnosis and examinations

Physical and diagnostic examination
Lassa fever is diagnosed using a blood test, a urine test (the presence of protein in the urine) or a throat swab. However, the diagnosis is difficult because the clinical course of the disease is very variable.

Differential diagnosis
Lassa fever is difficult to distinguish from other viral hemorrhagic fevers such as Ebola and other diseases that cause fever such as malaria, shigellosis (bacterial infection associated with diarrhea), typhoid (bacterial infection due to infected insect bite) and yellow fever (flu-like symptoms and jaundice).

Treatment via medicine

In non-endemic countries, rapid isolation of the affected patient(s) is necessary. Tracing possible contacts of the infected patient(s) is then necessary to prevent further outbreaks of the disease. The antiviral drug ribavirin is effective in treating Lassa fever if the patient receives it early in the disease. A vaccine is not available for this infectious disease. The doctor also treats Lassa fever supportively and symptomatically. He ensures that the patient is hydrated to prevent dehydration. Treating low blood pressure and oxygen therapy are also possible treatment options.

Lassa fever brings serious complications to pregnant women / Source: PublicDomainPictures, Pixabay

Prognosis of disease

Most patients recover within a month of the onset of the disease. Transient deafness, transient hair loss and impaired gait (ataxia) occur in some patients during the recovery process.


About 20% of symptomatic infections lead to serious complications, with the virus spreading to multiple organs such as the liver, spleen and kidneys. Sometimes the deafness is also permanent. Approximately 15-20% of hospitalized patients usually die within two weeks of the appearance of symptoms, usually as a result of irreversible hypovolemic shock. (there is insufficient blood in the body) The disease is also particularly serious in late pregnancy (third trimester), with death of the pregnant woman and/or loss of the fetus in more than 80% of cases.

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