Lassa and Ebola Viruses (African Outbreak Diseases)

Lassa fever is caused by Lassa virus, a single-stranded RNA arenavirus, endemic in West Africa (Nigeria, Sierra Leone, Liberia, Guinea), with reservoir in Mastomys natalensis (multimammate rat). Annual incidence 100,000-300,000 cases with 5,000 deaths in West Africa. Transmission via inhalation of dust contaminated with rodent urine/feces, ingestion of contaminated food, direct contact with rodents, person-to-person via blood/body fluids in healthcare settings, sexual transmission for up to 3 months post-recovery. Incubation 6-21 days. Clinical spectrum: 80% asymptomatic or mild, 20% severe with fever, malaise, headache, sore throat, retrosternal pain, cough, abdominal pain, diarrhea, vomiting, conjunctivitis, facial swelling, hemorrhage (gums, nose, GI tract), encephalopathy, sensorineural hearing loss (25% of survivors).

Ebola virus disease (EVD) is caused by Ebolavirus genus filoviruses with five species: Zaire ebolavirus (most pathogenic, 25-90% case fatality), Sudan, Bundibugyo, Tai Forest, Reston (non-pathogenic to humans). Reservoir is fruit bats (Pteropodidae). Major outbreaks: Zaire 1976 (initial discovery), West Africa 2013-2016 (largest, 28,646 cases, 11,323 deaths in Guinea, Liberia, Sierra Leone), DRC outbreaks, Uganda Sudan ebolavirus 2022. Transmission via direct contact with blood/body fluids of symptomatic individuals or deceased, healthcare-associated, traditional burial practices, fomites, sexual transmission for months after recovery, no airborne transmission. Incubation 2-21 days. Clinical course: dry phase (first 3-4 days, fever, headache, myalgia, fatigue), wet phase (vomiting, diarrhea, abdominal pain, hemorrhage in 30%), shock and multiorgan failure, recovery starts day 7-10 in survivors.

Diagnosis is by RT-PCR (gold standard), antigen detection (rapid diagnostic tests), serology (IgM, IgG ELISA), virus isolation in BSL-4 laboratory only, contact tracing critical for outbreak control. Treatment: Lassa fever — ribavirin (intravenous, most effective if started within 6 days of onset), supportive care with fluid management, electrolytes, blood products, ribavirin postexposure prophylaxis for high-risk contacts; Ebola — supportive care with aggressive fluid and electrolyte replacement, monoclonal antibody therapy (Inmazeb/atoltivimab+maftivimab+odesivimab and Ebanga/ansuvimab — both FDA-approved 2020 for Zaire ebolavirus), remdesivir, ZMapp (historical), favipiravir, convalescent plasma, vaccines (rVSV-ZEBOV/Ervebo for Zaire ebolavirus, Zabdeno+Mvabea two-dose), strict infection control with PPE (full body suits, double gloves, face shield, N95 respirators, dedicated facilities), traditional burial modifications, contact tracing with 21-day observation, post-recovery surveillance. Prevention via rodent control (Lassa), avoiding bats and infected animals, PPE for healthcare workers, vaccination of frontline workers, public health education, ring vaccination during outbreaks.