This is a mechanism module, not a specific disease. Do NOT create a `Viral_Hemorrhagic_Fever` Disease entry: the organ syndrome spans unrelated organisms, so under the infectious disease granularity ladder (design decisions section 3e, rules R4 and R24) the shared mechanism is this module and the membership is the `Viral_Hemorrhagic_Fevers` grouping. This module and that grouping together replace the former umbrella entry, which was the one instance the granularity checker reported as DOUBLE_MODELLED.
Disorder entries reference individual nodes via conforms_to (for example, "viral_hemorrhagic_fever_syndrome#Increased Vascular Permeability"). Key disease-specific substitutions at the trigger node: Ebola virus disease substitutes filovirus entry via endocytosis and NPC1, with macrophage and dendritic cell infection early; hemorrhagic fever with renal syndrome substitutes beta3 integrin-mediated, noncytopathic hantavirus infection of microvascular endothelium, with the permeability lesion driven by VEGF and bradykinin rather than by cytolysis; severe dengue substitutes secondary heterotypic infection with antibody-dependent enhancement, and the leak is brief and self-limiting rather than progressive. The organ emphasis substitutes too - renal for hantavirus, hepatic for yellow fever and Ebola - and is a property of the conforming entry, not of this module.
The module is deliberately two-armed rather than funnelled through a single hemostatic umbrella node. An earlier review of the former umbrella entry (PR dismech#8243) removed exactly such a parent node, on the ground that the directionality of umbrella-to-route edges was not supported by the cited sources, and atomized the four bleeding routes instead. That judgement is preserved here: the four hemostatic routes descend directly from the trigger, because the source states that both direct viral infection of host cells and the host response contribute to hemostatic dysregulation without ranking or sequencing the routes. The same review removed a bundled shock-and-organ-dysfunction node, so this module ends in individual phenotype readouts rather than in one composite consequence node.
There is no treatments block, and its absence is the finding rather than a gap. No therapy acts on this shared mechanism: supportive care is the cornerstone of management for most hemorrhagic fevers precisely because pathogen-targeted therapy is agent-specific (ribavirin for Lassa fever, monoclonal antibodies for Ebola virus disease, vaccines for a selected few). Those belong on the member disorder entries, and the cross-group statement of that asymmetry is recorded in the `Viral_Hemorrhagic_Fevers` grouping.
Modules bind GO and CL terms only and do not use chemical (CHEBI) or disease (MONDO) term bindings; the phenotypes block binds HP terms, following the precedent of `myelosuppression` and `drug_induced_liver_injury`, because the clinical readouts are what make this a hemorrhagic *fever* module rather than a generic endothelial one.
Which endothelial, coagulation-factor, consumptive-coagulopathy, and platelet mechanisms are genuinely shared across the hemorrhagic fevers, and which are specific to a virus, disease stage, or bleeding site?
KNOWLEDGE GAP
OPEN
vhf_shared_vs_agent_specific_bleeding_mechanisms
Attached to:
Endothelial Activation and Damage
Increased Vascular Permeability
Consumptive Coagulopathy
Decreased Coagulation Factor Production
Reduced Platelet Number
Platelet Dysfunction
This module represents recurring routes, not universal ones. Comparative evidence remains insufficient to assign the same causal weight or sequence to each route across all hemorrhagic fever viruses, which is why the four hemostatic routes are drawn in parallel from the trigger rather than ordered. Resolving this would say which of the four a conforming entry should be expected to declare, and would turn the module's parallel arms into a sequenced chain.
How faithfully do animal, conventional two-dimensional culture, and emerging microphysiological models reproduce human hemorrhagic fever vascular dynamics across different agents?
HUMAN MODEL MISMATCH
OPEN
vhf_human_vascular_model_fidelity
Attached to:
Endothelial Activation and Damage
Increased Vascular Permeability
Existing animal and cell-culture systems have produced the mechanistic insight this module rests on, but a vascular-model review specifically questions their fidelity to human in-vivo dynamics and presents microphysiological systems as promising rather than validated replacements. The module's two vascular nodes are therefore supported by evidence whose translational validity to human disease is itself the open question.
High Viremia and Vascular Target Infection
trigger
The shared upstream state of the syndrome. Early failure of antiviral immunity lets the virus reach high titre, and the circulating virus reaches the vascular endothelium and the mononuclear phagocyte compartment. What is conserved across agents is not the receptor, the entry route or the tissue tropism - those differ - but that a high systemic viral burden is presented to the vasculature and to myeloid cells. Conforming entries substitute their own agent, receptor and entry mechanism here.
Downstream
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Endothelial Activation and Damage
High-titre infection reaches the vasculature and acts on endothelial cells, which is the entry point of the vascular arm of the syndrome.
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Consumptive Coagulopathy
Direct viral infection of host cells and the host response to the virus both contribute to hemostatic dysregulation, of which consumption of coagulation components is one of the four routes the literature distinguishes.
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Decreased Coagulation Factor Production
Reduced coagulation factor availability is a second route from the same viral and host-response effects on the hemostatic system.
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Reduced Platelet Number
Loss of circulating platelets is a third route from the same viral and host-response effects on the hemostatic system.
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Platelet Dysfunction
Impaired platelet function is a fourth route from the same viral and host-response effects on the hemostatic system, separable from platelet loss because a normal count does not exclude it.
Show evidence (2 references)
"Their pathogenesis is characterized by early failure of antiviral immunity, high viremia, endothelial dysfunction, capillary leak, and coagulopathy."
This places early failure of antiviral immunity and high viremia at the head of the shared pathogenetic sequence, which is what this trigger node represents.
"Named after their common symptom hemorrhage, these viruses induce significant vascular dysfunction by affecting endothelial cells, altering immunity, and disrupting the clotting system."
This supports the vascular and myeloid compartments as the targets on which these viruses act, and names the endothelial, immune and clotting arms that the module then follows.
Endothelial Activation and Damage
amplifier
Activation or damage of the vascular endothelium is the recurring vascular lesion of the hemorrhagic fevers. Its proximate drivers vary among agents - direct cytopathic infection, noncytopathic infection with junctional destabilisation, cytotoxic T cell attack on antigen-presenting endothelium, or host mediators acting on an uninfected endothelium - and a conforming entry substitutes its own. What is conserved is that the endothelium stops behaving as an intact barrier.
Downstream
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Increased Vascular Permeability
Endothelial activation and damage disrupt barrier integrity and increase vascular permeability.
Show evidence (2 references)
"Named after their common symptom hemorrhage, these viruses induce significant vascular dysfunction by affecting endothelial cells, altering immunity, and disrupting the clotting system."
This supports endothelial involvement, immune alteration, clotting disruption, and vascular dysfunction as shared hemorrhagic fever mechanisms.
"Herein, we discuss the potential mechanisms leading to bleeding during VHF, which include a consumptive coagulopathy, decreased coagulation factor production, thrombocytopenia and platelet dysfunction, and endothelial cell activation and damage, resulting in increased vascular permeability."
This supports endothelial activation and damage, and the increased vascular permeability that follows, as mechanisms linked to hemorrhagic fever bleeding.
Increased Vascular Permeability
central effector
The rate-limiting lesion of the syndrome and the module's key conformance target. A microvascular endothelium that no longer restrains solute and plasma movement permits plasma leakage and intravascular volume loss. Every hemorrhagic fever funnels through this node; what differs by agent is its tempo and its severity, not whether it occurs. Conforming entries name the mechanism that produces it in their disease - VEGF-driven VE-cadherin destabilisation, bradykinin release, or direct cytopathic loss of the barrier.
Downstream
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Capillary leak
Increased vascular permeability is expressed clinically as capillary leak.
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Shock
Severe plasma leakage contributes to shock through intravascular volume depletion and hypotension.
Show evidence (2 references)
"Their pathogenesis is characterized by early failure of antiviral immunity, high viremia, endothelial dysfunction, capillary leak, and coagulopathy."
This names capillary leak as a distinct recurring feature of hemorrhagic fever pathogenesis, alongside the endothelial dysfunction upstream of it.
"Herein, we discuss the potential mechanisms leading to bleeding during VHF, which include a consumptive coagulopathy, decreased coagulation factor production, thrombocytopenia and platelet dysfunction, and endothelial cell activation and damage, resulting in increased vascular permeability."
The review directly links endothelial activation and damage to the increased vascular permeability this node represents.
Consumptive Coagulopathy
effector
Consumption of coagulation components is the first of the four hemostatic routes to bleeding. It is one potential route rather than a universal one: it is not asserted to occur in every hemorrhagic fever or to carry equal weight across agents.
Downstream
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Hemorrhage
Consumption of coagulation components contributes to hemorrhagic manifestations.
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Coagulopathy
Consumptive hemostatic dysfunction is clinically detected as coagulopathy.
Show evidence (2 references)
"Both direct effects from viral infection of host cells and indirect effects caused by the host response to the virus contribute to dysregulation of the hemostatic system."
This supports direct and host-response-mediated hemostatic dysregulation as the origin of this route.
"Herein, we discuss the potential mechanisms leading to bleeding during VHF, which include a consumptive coagulopathy, decreased coagulation factor production, thrombocytopenia and platelet dysfunction, and endothelial cell activation and damage, resulting in increased vascular permeability."
This directly identifies consumptive coagulopathy as a distinct bleeding mechanism in these infections.
Decreased Coagulation Factor Production
effector
Reduced production of coagulation factors is the second hemostatic route and is separable from consumption: a factor deficit arising from impaired synthesis, typically in the setting of hepatic involvement, is not the same lesion as one arising from consumption at sites of activation.
Downstream
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Hemorrhage
Reduced coagulation factor availability increases bleeding risk.
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Coagulopathy
Reduced coagulation factor availability contributes to an abnormal coagulation profile.
Show evidence (1 reference)
"Herein, we discuss the potential mechanisms leading to bleeding during VHF, which include a consumptive coagulopathy, decreased coagulation factor production, thrombocytopenia and platelet dysfunction, and endothelial cell activation and damage, resulting in increased vascular permeability."
This directly identifies decreased coagulation factor production as a distinct bleeding mechanism in these infections.
Reduced Platelet Number
effector
Loss of circulating platelets is the third hemostatic route. Its occurrence and its contribution to hemorrhage vary by agent; the dengue observation cited below is a worked instance and is not generalized to every hemorrhagic fever.
Downstream
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Thrombocytopenia
Reduced platelet number is clinically detected as thrombocytopenia.
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Hemorrhage
Reduced platelet number contributes to hemorrhagic manifestations.
Show evidence (2 references)
"In dengue virus infection, thrombocytopenia and platelet dysfunction occur."
This supports reduced platelet number in dengue as a representative, agent-specific instance of this route.
"Herein, we discuss the potential mechanisms leading to bleeding during VHF, which include a consumptive coagulopathy, decreased coagulation factor production, thrombocytopenia and platelet dysfunction, and endothelial cell activation and damage, resulting in increased vascular permeability."
This directly identifies thrombocytopenia as one of the bleeding mechanisms in these infections.
Platelet Dysfunction
effector
Abnormal platelet function is the fourth hemostatic route and is separate from platelet loss: platelets present in normal number may still fail to adhere, activate or aggregate. Its occurrence and importance differ by agent, and the dengue observation cited below is a worked instance rather than a cross-agent claim.
Downstream
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Hemorrhage
Platelet dysfunction contributes to hemorrhagic manifestations.
Show evidence (2 references)
"In dengue virus infection, thrombocytopenia and platelet dysfunction occur."
This supports platelet dysfunction in dengue as a representative, agent-specific instance of this route.
"Herein, we discuss the potential mechanisms leading to bleeding during VHF, which include a consumptive coagulopathy, decreased coagulation factor production, thrombocytopenia and platelet dysfunction, and endothelial cell activation and damage, resulting in increased vascular permeability."
This directly identifies platelet dysfunction as one of the bleeding mechanisms in these infections.