Virus wiki
Lassa Fever
Lassa fever is an arenavirus hemorrhagic fever endemic in parts of West Africa, associated with rodent reservoirs and nosocomial spread risk.
Snapshot: 5/10/2026, 11:00:51 AM · 1 tracked locations · 4,918 active cases (dataset)
Important
Virus Tracker provides aggregated outbreak monitoring for education and situational awareness. It is not medical advice, a diagnostic service, or a substitute for guidance from qualified health professionals or official public health agencies. Always consult licensed clinicians and authoritative sources for personal health decisions.
Overview
Mastomys rodents shed virus in urine and feces; humans become infected through contact with contaminated food or surfaces. Seasonal peaks align with agricultural and dry-season rodent-human interface patterns. Virus Tracker helps visualize regional case pressure alongside broader viral hemorrhagic fever differential diagnoses in surveillance briefings.
Transmission
Rodentborne exposure dominates; secondary transmission occurs through bodily fluids in healthcare and household settings without barrier precautions.
Symptoms & clinical notes
Fever, weakness, headache, sore throat, and in severe cases bleeding, shock, and organ dysfunction. Early supportive care improves outcomes; ribavirin may be used per protocol.
Prevention & control
Rodent control, food storage hygiene, safe burial practices, and rigorous healthcare PPE and triage reduce risk. Community trust accelerates reporting.
Surveillance context
Integrated human and environmental surveillance with rapid diagnostics strengthens containment. Cross-border coordination limits silent spread along trade routes.
Key metrics
Active cases (dataset)
4,918
Reported deaths
1,340
Pressure index
25.22%
Lassa Fever — global infection heat map
Country shading reflects relative active-case intensity from the current Virus Tracker dataset for this pathogen. Hover countries on desktop for counts.
Trajectory outlook
Trajectory (14d)
Regional analysis
Top regions by active cases
Top 1 tracked locations for Lassa Fever by active cases in the current dataset.
Threat intelligence visuals
Threat Matrix
Pressure (x) vs CFR (y) with bubble size by active cases
Source Reliability
Healthy sources
4
Unhealthy sources
3
Average confidence
42.0%
Confidence exposure
2,066
Health ratio
Severity by Region
Top affected regions
| Location | Active | Deaths |
|---|---|---|
| Nigeria (NG) | 4,918 | 1,340 |
FAQ
Is this page medical advice?
Virus Tracker provides aggregated outbreak monitoring for education and situational awareness. It is not medical advice, a diagnostic service, or a substitute for guidance from qualified health professionals or official public health agencies. Always consult licensed clinicians and authoritative sources for personal health decisions.
What does the pressure index mean on Virus Tracker?
Pressure index reflects active-case burden relative to recoveries in our models. It helps compare stressed outbreak zones within the dataset—it is not a clinical score.
How often is this wiki updated?
Figures refresh on the site’s ingestion and revalidation schedule (typically about every 30 minutes in production). Timestamps on the dashboard snapshot indicate the last build of the underlying dataset.
Why might the heat map not match official government totals?
We merge multiple open sources and fallbacks; reporting lag, testing policy, and geographic coverage differ by country. Use national health ministries for authoritative case definitions.