13/11/2025
Viral Hemorrhagic Fevers (VHFs) 🚫
Introduction
Viral Hemorrhagic Fevers (VHFs) are a group of severe, potentially life-threatening systemic illnesses caused by RNA viruses belonging to four major families: Arenaviridae, Filoviridae, Bunyaviridae, and Flaviviridae. The defining characteristic of these diseases is their ability to damage the vascular system (blood vessels), leading to increased capillary permeability, coagulation defects, and the potential for bleeding, or hemorrhage, along with generalized systemic illness and fever.
Pathogenesis
The severe symptoms of VHFs stem primarily from two core processes: vascular damage and coagulation defects. The viruses or the massive inflammatory response they trigger cause damage to the endothelial cells lining the blood vessels, resulting in an increase in vascular permeability, known as a capillary leak. This leakage allows plasma to escape the bloodstream, leading to severely low blood volume and hypovolemic shock. Simultaneously, the infection often triggers Disseminated Intravascular Coagulation (DIC), a condition where the body inappropriately forms small blood clots throughout the microvasculature, consuming the entire supply of clotting factors and platelets. Compounding this, certain VHFs cause liver necrosis, impairing the liver's ability to synthesize essential clotting proteins. The combined effect is severe bleeding and circulatory failure.
Epidemiology
VHFs are predominantly zoonotic diseases, meaning the viruses are naturally maintained in specific animal reservoirs, such as rodents (e.g., Lassa Fever, Hantavirus), bats (e.g., Ebola, Marburg), or arthropods like mosquitoes and ticks (e.g., Yellow Fever, Dengue, Crimean-Congo Hemorrhagic Fever). Because of this reliance on animal hosts, VHFs are typically geographically restricted to the areas where their reservoirs live (e.g., specific regions of Africa, South America, or Asia). Transmission to humans usually occurs through zoonotic spillover—contact
