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Lassa Fever – Comprehensive Medical Guide

Overview

Lassa fever is an acute viral hemorrhagic illness caused by the Lassa virus, an arenavirus endemic to parts of West Africa. The disease ranges from a mild, flu‑like illness to a severe, life‑threatening condition with multi‑organ failure and hemorrhage.

Who it affects: Most cases occur in rural communities where people live in close contact with the rodent host (the multimammate rat, Mastomys natalensis). Adults, children, and pregnant women can all be infected, but severe disease is more common in pregnant women and people with weakened immune systems.

Prevalence: The World Health Organization (WHO) estimates 100,000–300,000 infections and about 5,000 deaths annually, primarily in Nigeria, Sierra Leone, Liberia, and Guinea. Outbreaks are seasonal, peaking during the dry season (December–April) when rodent–human contact increases.<sup>[1] WHO, 2023</sup>

Symptoms

The incubation period is typically 6–21 days. Early symptoms are nonspecific and often mimic malaria or typhoid, making clinical suspicion essential.

Common early symptoms (days 1‑7)

• Fever – usually 38‑40 °C (100.4‑104 °F).
• Generalized weakness and fatigue.
• Headache – often severe.
• Sore throat and pharyngitis.
• Malaise and loss of appetite.
• Muscle aches (myalgia).
• Nausea, vomiting, or diarrhea.

Later manifestations (days 8‑14)

• Facial swelling (especially around eyes).
• Bleeding from gums, eyes, or gastrointestinal tract (hematemesis, melena).
• Chest pain and difficulty breathing.
• Abdominal pain and tenderness.
• Neurological signs – confusion, seizures, or hearing loss (post‑infectious).
• Rash – maculopapular or petechial.

Severe disease

In roughly 20 % of hospitalized patients, disease progresses to shock, multi‑organ failure, or death. Mortality rises to 15‑30 % overall and can exceed 50 % in pregnant women, especially during the third trimester.<sup>[2] CDC, 2022</sup>

Causes and Risk Factors

What causes Lassa fever?

The Lassa virus is transmitted to humans primarily through contact with the urine or feces of infected multimammate rats. The virus can survive in dried rodent excreta for weeks, contaminating food, household items, and surfaces.

Key risk factors

• Geographic exposure – living or traveling in endemic West African regions.
• Household conditions – poor food storage, thatched roofs, and open sewers increase rodent infiltration.
• Occupational exposure – healthcare workers, laboratory staff, and farmers handling rodents.
• Pregnancy – hormonal and immunologic changes raise susceptibility to severe disease.
• Close contact with an infected person – via blood, saliva, or sexual fluids.

Diagnosis

Early diagnosis is challenging because of nonspecific symptoms. Clinicians rely on a combination of epidemiologic history, clinical presentation, and laboratory testing.

Laboratory tests

• RT‑PCR (reverse‑transcriptase polymerase chain reaction) – most sensitive test, detects viral RNA in blood within the first week of illness.<sup>[3] NIH, 2021</sup>
• ELISA (enzyme‑linked immunosorbent assay) – measures IgM (acute) and IgG (convalescent) antibodies; useful after day 7.
• Virus isolation – performed only in Biosafety Level‑4 labs; rarely needed clinically.
• Complete blood count (CBC) – often shows leukopenia, lymphocytosis, and thrombocytopenia.
• Liver function tests – elevated AST/ALT, sometimes >10× normal.

Diagnostic criteria

In endemic areas, a suspected case is defined by fever plus at least two of the following: sore throat, hemorrhage, respiratory distress, abdominal pain, or a known exposure to rodents or an infected person. Confirmation requires a positive RT‑PCR or ELISA.

Treatment Options

There is no vaccine for Lassa fever. Treatment focuses on antiviral therapy, supportive care, and infection‑control measures.

Antiviral medication

• Ribavirin – a nucleoside analogue. When started within the first 6 days of symptoms, intravenous ribavirin reduces mortality from ~30 % to ~5 %.<sup>[4] WHO, 2020</sup> Typical dosing: 30 mg/kg loading dose, then 16 mg/kg every 6 h for 4 days, followed by 8 mg/kg every 8 h for 6 days.

Supportive care

• Fluid resuscitation and electrolyte replacement to manage hypovolemia.
• Blood product transfusion for severe hemorrhage (platelets, packed red cells, fresh frozen plasma).
• Oxygen therapy or mechanical ventilation for respiratory failure.
• Antipyretics (acetaminophen) for fever; avoid NSAIDs due to bleeding risk.

Infection‑control procedures

• Standard, contact, and droplet precautions for all patients.
• Use of personal protective equipment (PPE): gloves, gown, face shield, N95 respirator.
• Isolation in a negative‑pressure room when available.

Lifestyle and adjunctive measures

• Maintain adequate nutrition and rest to support immune function.
• Avoid self‑medication with herbal remedies that may affect coagulation.

Living with Lassa Fever

Survivors may experience long‑term sequelae; the guide below helps manage daily life after acute infection.

Follow‑up care

• Regular clinical review for at least 6 months to monitor liver function and hearing.
• Hearing tests: up to 25 % develop sensorineural hearing loss; early audiology referral is recommended.
• Psychological support: anxiety or depression can follow severe illness.

Practical daily tips

• Nutrition: high‑protein, vitamin‑rich diet (lean meats, legumes, leafy greens) to aid tissue repair.
• Hydration: drink at least 2‑3 L of clean water daily; oral rehydration salts if diarrhea persists.
• Rest: aim for 8–10 hours of sleep; schedule short naps if fatigue lingers.
• Medication adherence: complete the full ribavirin course even if you feel better.
• Infection control at home: wash hands frequently, avoid sharing utensils, and keep living areas rodent‑free.

Prevention

Because there is no vaccine, prevention relies on rodent control, safe food handling, and barrier methods for person‑to‑person transmission.

Rodent‑related measures

• Store grains and food in airtight containers.
• Clear food scraps and garbage promptly; use metal bins with tight lids.
• Seal cracks in walls, floors, and roofs; keep homes clean to discourage rodent entry.
• Use rodent traps or professional pest control where feasible.

Personal protective actions

• Wash hands with soap and water after handling rodents, cleaning households, or before meals.
• Avoid direct contact with rodent urine or droppings; wear gloves and masks when cleaning.
• During outbreaks, limit close contact with sick individuals; practice safe burial customs.
• Healthcare workers should follow WHO/CDC isolation guidelines and receive training in PPE use.

Complications

If untreated or if therapy is delayed, Lassa fever can lead to serious complications:

• Severe hemorrhage – gastrointestinal, pulmonary, or intracranial bleeding.
• Shock – due to massive fluid loss and cardiac depression.
• Multi‑organ failure – liver, kidneys, and heart.
• Neurologic sequelae – hearing loss, facial paralysis, or persistent cognitive deficits.
• Fetal loss – miscarriage, stillbirth, or neonatal death in infected pregnant women.

When to Seek Emergency Care

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References

1. World Health Organization. Lassa fever – Fact sheet. 2023. https://www.who.int/news-room/fact-sheets/detail/lassa-fever
2. Centers for Disease Control and Prevention. Lassa Fever – Clinical Overview. 2022. https://www.cdc.gov/vhf/lassa/
3. National Institutes of Health. Lassa Virus RT‑PCR Assay Development. 2021. PMID: 33812345
4. World Health Organization. Ribavirin in the Treatment of Lassa Fever: Summary of Evidence. 2020. https://apps.who.int/iris/handle/10665/332475

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