Plasma leakage and coagulopathy are the fundamental pathological changes responsible for clinical manifestations, morbidity, and mortality in DHF. A complex interplay between immunological mechanisms with viral and host factors are implicated in the pathogenesis. Both humoral and cell-mediated immune mechanisms eventually result in the release of cytokines responsible for changes in the selective microvascular permeability and the resultant plasma leakage.
Plasma leakage progresses either rapidly or slowly to cease completely and predictably after 24 to 48 hours of onset, raising the possibility of existence of underlying functional change rather than structural damage and in ammation in the vasculature. the influence of DENV on endothelial cells may be direct or indirect via release of mediators from infected or activated immune cells. Changes in the expression of adhesion molecules, enzymes, and cytokine receptors on endothelial cells are implicated in increasing the vascular permeability as well as activation of the coagulating system.