Lassa fever natural history, complications and prognosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]; Associate Editor(s)-in-Chief: Ammu Susheela, M.D. [3]

Synonyms and keywords: Lassa hemorrhagic fever; LHF

Overview

Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes into contact with the virus. The most common complication of Lassa fever is deafness. Various degrees of deafness occur in approximately one-third of cases, and in many cases hearing loss is permanent. Spontaneous abortion is another serious complication. Approximately 15%-20% of patients hospitalized for Lassa fever die from the illness. However, overall only about 1% of infections with Lassa virus result in death. The death rates are particularly high for women (greater than 80%) in the third trimester of pregnancy, and for fetuses, about 95% of which die in the uterus of infected pregnant mothers.

Natural History

• Some of the characteristic symptoms of the virus include: fever, muscle aches, sore throat, nausea, vomiting, chest and abdominal pain, weakness, cough, headache, exudative pharyngitis, anemia, low blood pressure, and diarrhea. Because its symptoms are similar to other febrile illness found in Africa, Lassa virus is hard to diagnose.
• It can eventually can cause pulmonary edema, pleural and pericardial effusion, facial edema, bleeding from mucosal surfaces, neurological complications, deafness, lymphocytopenia, thrombocytopenia, and ascites. Often sore throat, vomiting, and bleeding are associated with higher fatality. There are four clinical stages of Lassa fever.
• The first stages occurs within the first three days and its symptoms include a high fever, weakness, and a general depression in activity. The second stage transpires from day 4 to day 7 where the patient experiences some of the more common/characteristic symptoms as stated above. The third stage begins at the seventh day and includes more severe symptoms such as: facial edema, convulsions, mucosal bleeding, internal bleeding, and disorientation. The fourth stage usually occurs after the 14th day and ends in coma and death.
• Only 20% of people who contract Lassa fever have severe multisystem trauma, meaning that 80% of people have only the milder symptoms. It has also been found that most cases of Lassa fever occur as the seasons change from dry to wet.

While Lassa fever is mild or has no observable symptoms in about 80% of people infected with the virus, the remaining 20% have a severe multisystem disease.

• The high degree of seroprevalence of LASV-specific antibodies in the general population residing in the endemic regions, although highly variable depending on the geographical location (from 1.8% to 55%) [ indicates that most infections are mild or possibly even asymptomatic and do not result in hospitalization. This is also supported by the findings indicating a high incidence of LASV-specific seroconversion, from 5% to 20% of the nonimmune population per year.

• Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes into contact with the virus. For the majority of Lassa fever virus infections (approximately 80%), symptoms are mild and are undiagnosed.
• Mild symptoms include slight fever, general malaise and weakness, and headache. In 20% of infected individuals, however, disease may progress to more serious symptoms including hemorrhaging (in gums, eyes, or nose, as examples), respiratory distress, repeated vomiting, facial swelling, pain in the chest, back, and abdomen, and shock.
• Neurological problems have also been described, including hearing loss, tremors, and encephalitis. Death may occur within two weeks after symptom onset due to multi-organ failure.
• Clinical stages of Lassa fever (adapted from McCarthy)

Stage	Symptoms	Days
Stage 1	High fever of 39°C with peaks of 40°C-41°C, malaise, weakness	Day1 -day 3
Stage 2	Headache, backache, chest pain, exudative sore throat with white patches, abdominal pain, diarrhea, nausea, vomiting, low blood pressure, anemia, proteinuria, conjunctivitis	Day4 -day 7
Stage 3	Mucosal bleeding, internal bleeding, facial edema, confusion, disorientation and convulsion	>7 days
Stage 4	Coma, death	>14 days

Clinical signs and symptoms Lassa Fever CDC[1]

Complications

• Complications of Lassa fever include the following.

Sensorineural Deafness

• The most common complication of Lassa fever is deafness.
• Occurs in 1/3rd of the cases.
• Various degrees of deafness occur in approximately one-third of infections, and in many cases hearing loss is permanent.
• As far as is known, severity of the disease does not affect this complication: deafness may develop in mild as well as in severe cases.
• It could be unilateral or bilateral.

Lassa Fever in Pregnancy

• Increased mortality in 3rd trimester of more than 30% to the mother.
• Increased viremia in pregnant woman.
• Evacuation of the uterus improves mother's chance of survival.
• Placental infection of the fetus.
• Spontaneous abortion is a serious complication of infection with an estimated 95% mortality in fetuses of infected pregnant mothers.
• Increased fetal and neonatal mortality of more than 85%.

Lassa Fever in Children

Swollen Baby Syndrome

• Edema.
• Abdominal distention.
• Bleeding.
• Poor prognosis.

Prognosis

• Approximately 15%-20% of patients hospitalized for Lassa fever die from the illness. However, only 1% of all Lassa virus infections result in death. Prognosis of Lassa fever is poor if its associated with following features.

• Increased viremia.
• Serum AST level > 150 IU/L
• Bleeding.
• Encephalitis.
• Edema
• Third trimester of pregnancy.

References

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