Lassa Fever: Symptoms, Types, Causes and Treatment

Lassa fever is a significant public health threat in West Africa, often making headlines due to its rapid outbreaks and severe health consequences. Caused by the Lassa virus, this acute viral illness can range from mild symptoms to deadly hemorrhagic fever. Understanding its symptoms, types, causes, and the best approaches to treatment is crucial for affected communities and healthcare workers alike. This article takes a deep dive into the key aspects of Lassa fever, drawing on the latest scientific findings and outbreak reports.

Symptoms of Lassa Fever

Lassa fever doesn’t always announce itself loudly at first. Many people infected may experience only mild symptoms, while others can quickly become critically ill. Recognizing the early warning signs and understanding how the disease progresses is vital for prompt treatment and improving survival rates.

Symptom	Description	Severity Range	Source(s)
Fever	Sudden onset, often high	Mild to severe	1238
Myalgia	Muscle aches, fatigue	Mild to moderate	132
Sore Throat	Painful, may be severe	Mild to moderate	132
Vomiting	Nausea and/or vomiting	Mild to severe	132
Abdominal Pain	Discomfort or cramps	Mild to severe	132
Chest Pain	Retrosternal pain	Mild to severe	23
Hemorrhage	Bleeding (nose, gums, etc.)	Severe/advanced	1278
Neurological	Hearing loss, tremors, confusion	Severe/advanced	127

Table 1: Key Symptoms of Lassa Fever

Early Symptoms

Lassa fever typically begins with non-specific symptoms that can easily be mistaken for common tropical illnesses like malaria or typhoid:

• Fever: The most frequent early symptom, often high and persistent.
• General malaise: Fatigue, weakness, and body aches (myalgia).
• Sore throat: Sometimes severe, making swallowing difficult.
• Headache: Common and can be intense.
• Nausea, vomiting, and abdominal pain: Gastrointestinal symptoms are frequent, especially in more severe cases 1238.

Progression to Severe Disease

For some, symptoms escalate:

• Chest pain: Particularly pain behind the sternum (retrosternal).
• Diarrhea: May develop alongside vomiting.
• Bleeding: In severe cases, patients may experience internal and external bleeding, such as from the gums, nose, or gastrointestinal tract.
• Neurological complications: These can include tremors, seizures, confusion, and even encephalitis (inflammation of the brain).
• Hearing loss: Notably, survivors often report some degree of permanent hearing loss, a unique and lingering effect of the disease 12378.

Asymptomatic and Mild Cases

Importantly, not all infected individuals become critically ill. It is estimated that about 80% of Lassa virus infections are mild or even asymptomatic, which can make containment and diagnosis challenging 234.

Types of Lassa Fever

Lassa fever does not come in neatly separated “types” as some diseases do, but the clinical spectrum is broad, ranging from silent infections to severe, life-threatening illness. Understanding these variations helps clinicians and public health officials tailor their response.

Type	Features	Outcome	Source(s)
Asymptomatic	No noticeable symptoms	Full recovery	234
Mild	Mild fever, malaise, minor aches	Recovery	238
Moderate	Pronounced symptoms, no organ failure	May recover with care	238
Severe	Hemorrhage, shock, organ failure, neurological	High mortality risk	2178

Table 2: Clinical Presentations of Lassa Fever

Asymptomatic and Mild Illness

• Asymptomatic: Many people, especially in endemic regions, may acquire the virus and show no symptoms at all. These cases are only detected by antibody tests and contribute to the silent spread of Lassa fever 234.
• Mild illness: Others may have a brief fever, mild aches, or sore throat, and recover without medical intervention.

Moderate Illness

• Symptoms are more intense and may include persistent fever, gastrointestinal discomfort, and general malaise.
• These patients often require supportive care but may recover without complications if managed promptly 238.

Severe and Complicated Cases

• Severe Lassa fever is characterized by:
  • Hemorrhagic manifestations (bleeding)
  • Hypotension (low blood pressure) and shock
  • Multiorgan failure (especially liver and kidney)
  • Neurological involvement such as seizures or encephalitis
• These cases have a significantly higher risk of death, particularly in hospitalized patients, where case fatality rates may reach 10–20% 1278.
• Pregnant women, especially in the third trimester, are at particular risk of severe complications and poor outcomes 78.

Complications and Long-Term Effects

• Hearing loss: Up to one-third of survivors may experience varying degrees of permanent hearing loss.
• Other sequelae: Neurological deficits, prolonged weakness, and, rarely, psychiatric complications 127.

Causes of Lassa Fever

Understanding what triggers Lassa fever outbreaks is essential in both preventing and controlling the disease. At its core, Lassa fever is a classic example of a zoonotic infection—one that jumps from animals to humans.

Cause	Description	Transmission Route	Source(s)
Lassa virus	Single-stranded RNA virus	Rodent to human, human to human	1345678
Rodent vector	Mastomys natalensis (multimammate rat)	Feces, urine, saliva	134678
Human-to-human	Contact with infected fluids	Blood, secretions, nosocomial	478
Environmental	Poor hygiene, contamination	Food, household items	8

Table 3: Causes and Transmission of Lassa Fever

The Lassa Virus

• Lassa fever is caused by the Lassa virus, a member of the Arenaviridae family. It is a single-stranded RNA virus with the ability to rapidly replicate and evade the human immune system 1356.

Animal Reservoir: Mastomys natalensis

• Primary host: The multimammate rat, Mastomys natalensis, is the natural reservoir for the Lassa virus 134678.
• Transmission: These rodents shed the virus in their urine, feces, and saliva. Humans typically become infected through:
  • Ingesting contaminated food or water
  • Contact with household items or surfaces contaminated with rodent excreta
  • Direct contact with the rodents themselves (handling, preparing as food) 348

Human-to-Human Transmission

• Direct contact: Infection can also spread between humans, especially in healthcare settings or within families.
• Routes: Exposure to blood, tissue, secretions, or excretions of an infected person is the primary risk.
• Nosocomial outbreaks: Hospital settings are particularly vulnerable to outbreaks, especially where infection control practices are inadequate 478.
• Sexual transmission: The virus can persist in bodily fluids (notably semen) even after recovery, raising the possibility of sexual transmission 412.

Environmental and Social Factors

• Outbreaks are more common where:
  • Rodent populations are high and often enter homes.
  • Food storage and hygiene practices are poor.
  • Healthcare facilities lack resources for infection control 8.
• Social practices, such as handling rodents as food or poor hand hygiene, further increase risk 8.

Treatment of Lassa Fever

A timely and effective treatment strategy can be the difference between life and death for Lassa fever patients. While supportive care remains the cornerstone, recent advances and debates around antivirals like ribavirin and favipiravir are shaping the future of Lassa fever management.

Treatment	Description	Effectiveness/Limitations	Source(s)
Supportive care	Hydration, symptom relief, monitoring	Essential for all patients	258
Ribavirin	Antiviral, best if given early	Most effective <6 days after onset; debated for mild cases	28910
Favipiravir	Investigational antiviral	Promising, limited human data	1112
Monoclonal antibodies	Under development	Not yet approved	26
Infection control	Isolation, PPE, hygiene	Prevents human-to-human spread	78

Table 4: Treatment Approaches for Lassa Fever

Supportive Care

• Basics: Hydration, fever control, pain management, and monitoring for complications are crucial.
• Hospitalization: Severe cases require close observation, management of bleeding, and treatment of shock or organ failure 258.

Antiviral Therapy

Ribavirin

• Gold standard: Ribavirin, a nucleoside analog, is currently the only widely accepted antiviral for Lassa fever.
• Timing is critical: It is most effective when administered within the first six days of illness. Early treatment dramatically reduces mortality, especially in high-risk patients (those with high viral loads or elevated liver enzymes) 928.
• Limitations: Its benefit in mild cases is in question, with some studies suggesting it may not be helpful or could even increase risks in those without severe disease 10.
• Administration: Given intravenously or orally, depending on severity and resource availability.

Favipiravir

• Emerging option: Favipiravir, another antiviral, has shown effectiveness in animal models and limited human cases—sometimes in combination with ribavirin—but is not yet standard therapy 1112.

Monoclonal Antibodies

• Future hope: Experimental monoclonal antibody therapies are under development and hold promise for targeted treatment in the future 26.

Infection Control and Prevention

• Isolation: Patients should be isolated to prevent nosocomial (hospital-acquired) transmission.
• Protective equipment: Healthcare workers must use gloves, masks, gowns, and other personal protective equipment (PPE) 78.
• Disinfection: Rigorously cleaning and disinfecting contaminated surfaces and safely disposing of waste is essential 8.

Post-Exposure Prophylaxis

• Ribavirin may also be given to people who have had high-risk exposures as a preventive measure, though data are limited 98.

Ongoing Research

• No approved vaccine: Despite ongoing research and vaccine candidates in development, no vaccine is currently available for Lassa fever 56.
• Need for better treatments: Improved antivirals and supportive therapies are a high priority due to the disease’s high fatality rate and potential for outbreaks 625.

Conclusion

Lassa fever remains a challenging and deadly disease, especially in West Africa. While much has been learned, gaps remain in prevention, rapid diagnosis, and definitive treatment. Knowledge and vigilance are key to controlling its spread and improving outcomes.

Key Takeaways:

• Symptoms: Range from mild fever to severe hemorrhage and neurological complications; hearing loss is common in survivors.
• Types: The spectrum varies from asymptomatic infections to severe, life-threatening disease.
• Causes: Result from infection with the Lassa virus, typically transmitted by Mastomys natalensis rodents, but also spread between humans.
• Treatment: Supportive care is vital; ribavirin is effective if given early but has limitations; new therapies are in development; no vaccine exists yet.

By staying informed and supporting research, we can move closer to better control and eventual eradication of Lassa fever.