Lassa fever natural history, complications and prognosis
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ammu Susheela, M.D. [2]
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
Incubation Period
- Infected patients remain asymptomatic for 3 to 21 days following exposure.[1]
Development of Clinical Manifestations
- The majority of patients experience no or mild symptoms. Only a minority (approximately 15-20%) of patients experience multiorgan dysfunction, and typically 5-15% of infected patients die of Lassa fever.
- Patients typically first develop persistent high-grade fever (39 °C to 41 °C) and other non-specific symptoms, such as muscle aches, conjunctival injection, headache, sore throat, nausea, and vomiting.
- If left untreated, the majority of patients self-resolve without any intervention.
- In a minority of cases, patients may develop worsening abdominal/chest pain, temporary/permanent deafness, facial edema, mucosal bleeding and hemorrhage, pulmonary edema, pleural/pericardial effusions or ascites, multi-organ failure, and shock.
- Prolonged and worsening symptoms are usually associated with worsening prognosis, typically resulting in convulsions, encephalitis, seizures, coma and finally death.
- The following table demonstrates the 4 clinical stages of Lassa fever (adapted from McCarthy et al. 2002[2])
| Stage | Symptoms | Days |
| Stage 1 | High-grade fever (39-41 °C), malaise, weakness | Day1 -day 3 |
| Stage 2 | Headache, backache, chest pain, sore throat with exudation, abdominal pain, diarrhea, nausea, vomiting, hypotension, 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 |
Complications
Complications of Lassa fever include the following:
- Sensorineural Deafness
- The most common complication of Lassa fever is deafness (1/3 of patients)
- Deafness may be either temporary or permanent and may either by unilateral or bilateral.
- Deafness does not seem to be associated with the severity of disease and may develop equally among patients with mild or severe infections.
- Spontaneous abortion among pregnant women
- Hepatitis and hepatic necrosis
- Splenic necrosis
- Adrenocortical necrosis
- Pulmonary alveolar edema
- Interstitial pneumonitis
- Lymph node histiocytosis
- Mucosal (e.g. GI) bleeding
- Renal tubular injury and interstitial nephritis
- Swollen baby syndrome (edema and bleeding among fetuses)
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[3].
- Increased viremia.
- Serum AST level > 150 IU/L
- Bleeding.
- Encephalitis.
- Edema
- Third trimester of pregnancy.
References
- ↑ Günther S, Lenz O (2004). "Lassa virus". Crit Rev Clin Lab Sci. 41 (4): 339–90. doi:10.1080/10408360490497456. PMID 15487592.
- ↑ McCarthy M (2002). "USA moves quickly to push biodefence research". Lancet. 360 (9335): 732. doi:10.1016/S0140-6736(02)09938-5. PMID 12296302.
- ↑ "The Centers for Disease Control and Prevention".