The Platelet–Virus Axis in Human Disease

Platelets have traditionally been viewed as passive cellular elements involved in hemostasis and vascular integrity. However, growing evidence over the last decade has radically changed this paradigm, revealing platelets as dynamic immune and inflammatory effectors that actively participate in host-pathogen interactions. In viral infections, platelets are not merely innocent bystanders but represent key players in a bidirectional and tightly regulated platelet-virus axis that influences viral dissemination, immune activation, endothelial dysfunction, and the development of thrombotic and hemorrhagic complications. Several clinically relevant viruses, including SARS-CoV-2, influenza virus, HIV, dengue virus, and viral hemorrhagic fever-associated pathogens, have been shown to directly or indirectly interact with platelets through surface receptors, immune complexes, and inflammatory mediators, leading to platelet activation, phenotypic reprogramming, and accelerated clearance. These processes contribute to the paradoxical coexistence of thrombocytopenia and hypercoagulability that characterizes many severe viral diseases. Moreover, platelets can act as immune sentinels by sensing viral components, releasing cytokines and chemokines, forming platelet-leukocyte aggregates, and modulating both innate and adaptive immune responses, thereby shaping the clinical course of infection. In this review, we synthesize current evidence on the molecular and cellular mechanisms governing virus-platelet interactions, with particular emphasis on their role in immune-thrombosis, endothelial injury, and organ dysfunction. We further discuss the clinical implications of platelet dysregulation in viral infections, including its potential value as a biomarker of disease severity and as a therapeutic target. Understanding the platelet-virus axis provides a unifying framework to explain the thrombo-inflammatory phenotype of viral diseases and may open new avenues for risk stratification and targeted interventions in affected patients.