Endothelial cell tropism or endotheliotropism is a type of tissue tropism or host tropism that characterizes an pathogen's ability to recognize and infect an endothelial cell. Pathogens, such as viruses, can target a specific tissue type or multiple tissue types. Like other cells, the endothelial cell possesses several features that supports a productive viral infection a cell including, cell surface receptors, immune responses, and other virulence factors.[1] Endothelial cells are found in various tissue types such as in the capillaries, veins, and arteries in the human body. As endothelial cells line these blood vessels and critical networks that extend access to various human organ systems, the virus entry into these cells can be detrimental to virus spread across the host system and affect clinical course of disease. Understanding the mechanisms of how viruses attach, enter, and control endothelial functions and host responses inform infectious disease understanding and medical countermeasures.