Viral hemorrhagic fevers

Causes and transmission

VHFs are caused by viruses from several families, including filoviruses, arenaviruses, bunyaviruses and flaviviruses. Well-known examples include Ebola and Marburg (filoviruses), Lassa (an arenavirus), hantaviruses and Crimean-Congo hemorrhagic fever (bunyavirus-related), and some severe forms of yellow fever (a flavivirus). Reservoirs are frequently wild animals or arthropod vectors; transmission to humans can be zoonotic, vector-borne, or by direct contact with infected bodily fluids. Public health summaries and guidance are available at health resources.

Signs, course and complications

Clinical presentation ranges from a mild febrile illness to rapid, life-threatening disease. Early symptoms commonly include fever, malaise, muscle pain and headache. In severe cases patients may develop bleeding from mucous membranes or puncture sites, low blood pressure, shock and organ failure. The course and severity depend on the specific virus, host factors and access to supportive care. Clinical outlines and case definitions can be found at clinical guidance.

History and notable outbreaks

Some VHFs have produced notable epidemics in recent decades, most prominently Ebola virus disease in parts of Africa since the late 20th century, which prompted advances in clinical care, diagnostics and vaccine development. Historically, VHFs have also been considered among many hypotheses about past epidemics; for instance, they were once suggested as a possible cause of medieval plagues, although the consensus attributes the Black Death mainly to bubonic plague historical discussion.

Prevention, treatment and public health importance

Prevention strategies vary: vector control and reducing exposure to animal reservoirs are important for zoonotic VHFs; strict infection control and barrier precautions prevent person-to-person spread during outbreaks. Some VHFs have effective vaccines (for example certain yellow fever and recently developed Ebola vaccines), while treatments are mostly supportive, though antiviral agents and monoclonal antibodies exist or are under study for specific viruses. Guidance on control measures is provided by public health agencies at prevention guidance and by outbreak reports at outbreak summaries.

• Key characteristics: fever, possible bleeding, vascular leak, multiorgan involvement.
• Common reservoirs/vectors: rodents, bats, ticks, mosquitoes.
• Public health response: surveillance, isolation, contact tracing, vaccination when available.

Because VHFs encompass several unrelated viruses with overlapping clinical pictures, laboratory testing is essential for diagnosis, and coordinated public health measures are critical to limit spread and reduce mortality.