Question
Viral haemorrhagic fever.
Answer
Viral haemorrhagic fevers (VHFs) are a group of severe, often life-threatening febrile illnesses caused by several unrelated RNA virus families, sharing a common ability to cause increased vascular permeability, coagulopathy, and haemorrhagic manifestations.
Causative virus families and examples:
- Filoviridae — Ebola virus, Marburg virus — cause among the most severe VHFs, with very high case-fatality rates; transmitted by contact with infected bodily fluids, with a natural reservoir believed to be fruit bats.
- Flaviviridae — Dengue virus (dengue haemorrhagic fever), Yellow fever virus, Kyasanur Forest Disease virus (an important VHF endemic to parts of India) — mosquito/tick-borne.
- Bunyavirales (order) — Crimean-Congo Haemorrhagic Fever virus (tick-borne), Hantavirus (rodent-borne, causing haemorrhagic fever with renal syndrome), Rift Valley Fever virus (mosquito-borne/animal contact).
- Arenaviridae — Lassa fever virus (rodent-borne, endemic to West Africa).
Pathogenesis (shared general principles): the causative viruses typically infect and damage vascular endothelium (directly or via triggering an intense host inflammatory/cytokine response), causing increased capillary permeability, plasma leakage, and, in many, direct or immune-mediated impairment of coagulation — together producing the characteristic combination of hypotension/shock and bleeding tendency (petechiae, mucosal bleeding, and, in severe cases, major internal haemorrhage).
Clinical features: fever, malaise, myalgia progressing (in severe cases) to hypotension, shock, and haemorrhagic manifestations (from mild petechiae/mucosal bleeding to severe, life-threatening haemorrhage); specific additional features vary by causative virus (e.g., jaundice in yellow fever, renal involvement in hantavirus/Hantaan infection).
Laboratory diagnosis: RT-PCR for viral RNA (the primary diagnostic method for most agents); serology (IgM/IgG ELISA); viral culture/isolation is hazardous and generally restricted to specialized high-biosafety-level (BSL-4) reference laboratories for the most dangerous agents (e.g., Ebola, Marburg, Lassa, CCHF).
Management/prevention: primarily supportive care (fluid/electrolyte management, blood product support); strict barrier nursing/isolation precautions given the risk of person-to-person transmission via infected bodily fluids for several of these agents (notably filoviruses, Lassa, CCHF); vector/reservoir control (mosquito/tick control, rodent control) and, where available, vaccination (e.g., yellow fever vaccine, an Ebola vaccine now available for outbreak response) for prevention.