Lassa fever is an acute viral haemorrhagic illness found mainly in West Africa. It is caused by the Lassa virus and is linked to rodent-to-human transmission.
🐀 Cause & Transmission
Lassa fever spreads mainly through:
- Contact with infected Mastomys natalensis rats
- Contact with urine or faeces of infected rodents
-
Person-to-person spread through:
- Blood
- Bodily fluids
- Contaminated medical equipment
It is most common in healthcare or household settings with poor infection control.
🌍 Regional Impact
Lassa fever is endemic in West Africa, including:
- Nigeria
- Sierra Leone
- Liberia
- Guinea
- Ghana
- Mali
- Benin
📊 Estimated impact:
- 100,000–300,000 cases per year
- Around 5,000–10,000 deaths annually
⚠️ Symptoms
Early (mild cases – around 80%)
- Fever
- Fatigue
- Headache
- General weakness
- Malaise (feeling unwell)
Severe cases (around 20%)
- Vomiting
- Bleeding (haemorrhage)
- Swelling (including face)
- Respiratory distress
- Shock
Symptoms usually begin 7–21 days after exposure.
🧠 Complications
Lassa fever can lead to serious long-term or life-threatening outcomes:
- Severe internal bleeding
- Organ failure
- Death (especially without treatment)
- Permanent hearing loss (about 1 in 3 cases)
-
High risk in pregnancy:
- Up to 95% fetal mortality rate
🧪 Treatment
Treatment is most effective when started early:
- Antiviral medication: ribavirin
-
Supportive care:
- Fluid replacement
- Oxygen support
- Hospital monitoring
Early diagnosis significantly improves survival chances.
🛡️ Prevention
Public health and CDC guidance includes:
- Controlling rodent populations
- Storing food in rodent-proof containers
- Maintaining hygiene in homes and food areas
- Using PPE in healthcare settings
- Avoiding contact with bodily fluids of infected individuals
📊 Prognosis
- Most cases are mild or moderate
- Severe cases can become life-threatening within 14 days
- Early treatment improves outcomes significantly
- Without treatment, mortality risk increases sharply
🔬 Key Idea
Lassa fever is a zoonotic viral disease (from animals to humans) where:
- Rodents are the main source
- Early symptoms look like flu
- Severe cases escalate quickly into haemorrhagic illness
🧠 Study Questions (Answers found in module text)
🔍 Understanding
- What animal is mainly responsible for spreading Lassa fever?
- What are the early symptoms of Lassa fever?
- What treatment is used for Lassa fever?
⚠️ Severity & Risk
- What percentage of cases become severe?
- Why is Lassa fever especially dangerous in pregnancy?
- What complications can occur in survivors?
🔗 Transmission & Prevention
- How does Lassa fever spread between humans?
- What steps help prevent infection?
- Why is rodent control important in prevention?
📌 Final Summary
Lassa fever is a serious viral disease that:
- Starts like a mild flu
- Can progress into severe haemorrhagic illness
- Is spread mainly through rodents
- Requires early treatment for better survival
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