Person-to-person — Person-to-person transmission occurs through direct contact of broken skin or unprotected mucous membranes with virus-containing body fluids from a person who has developed signs and symptoms of illness [60]. The most infectious body fluids are blood, feces, and vomit. Ebola virus has also been detected in urine, semen, and breast milk. Saliva and tears may also harbor the virus. Thus, contact with any of these fluids can pose potential risk. At present, it is unclear whether infectious virus exists in sweat [61]. As described below, such person-to-person transmission leads to outbreaks [40].
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..PATHOGENESIS — Ebola virus enters the body through mucous membranes, breaks in the skin, or parenterally. The pathogen infects many cell types, including monocytes, macrophages, dendritic cells, endothelial cells, fibroblasts, hepatocytes, adrenal cortical cells, and epithelial cells [88]. Because of the difficulty of performing clinical studies under outbreak conditions, almost all data on the pathogenesis of Marburg and Ebola virus diseases have been obtained from laboratory experiments employing mice, guinea pigs, and a variety of nonhuman primates.
Cell entry and tissue damage — Whatever the point of entry into the body, macrophages and dendritic cells are probably the first cells to be infected. Filoviruses replicate readily within these ubiquitous "sentinel" cells, causing their necrosis and releasing large numbers of new viral particles into extracellular fluid [13,89] (figure 1). Spread to regional lymph nodes results in further rounds of replication, followed by dissemination of virus to dendritic cells and fixed and mobile macrophages in the liver, spleen, thymus, and other lymphoid tissues......................................