These organs contain high numbers of monocytes and macrophages. Migration of infected monocytes and macrophages into surrounding tissues or transport of free virus via the lymph-or bloodstream is believed to facilitate the dissemination to multiple organs, resulting in a systemic infection [203, 204] . Cell-free virus has been observed in the tissue and organs of infected animals, and high levels of virus have been detected in the blood [12] [13] [14] 130, 194, 195, 205, 206] . Besides monocytes, macrophages, and dendritic cells, a wide range of cell types including hepatocytes, adrenal cortical and medullary cells and fibroblasts are permissive to MARV infection [12, 14, [192] [193] [194] [195] 197, 201, 207] . Endothelial cells are late target cells during MARV infection in multiple tissues. Whether or not replication of MARV in endothelial cells is associated with the observed vascular impairment during MVD is a matter of debate [64, 194] . Only low numbers of infected endothelial cells are observed in NHP infection and therefore changes in the endothelium are likely caused by paracrine effects of cytokines [14] .