This aside is a “nerd boost” for the main article found here.
Those immune cells infected by Ebola are monocytes, macrophages, and dendritic cells. These are all cells whose mission is to respond quickly to invasions by foreigners. Monocytes circulate throughout your bloodstream and once they enter into tissue (be it lung, liver, heart, or spleen), they morph into either macrophages (literally “big eaters”) or dendritic cells (very good at presenting evidence of infection to other immune cells). Within these tissues, macrophages and dendritic cells are situated at prime locations to monitor the entry of foreign pathogens (including Ebola).
One of the cytokines (again the words used for communication) normally produced upon infection by viruses is called Interferon. Interferons tell infected cells to slow down or stop the process of making DNA and protein so that the virus can’t hijack those functions to make more virus. Interferons also tell infected cells to identify themselves to immune cells so that if needed those cells can be killed. They do this by displaying bits of the virus on the cell surface. Kind of like waving a red flag to attract the attention of immune cells (particularly T cells) that are well-suited for eliminating infections. Ebola prevents these defense mechanisms from happening by making proteins, VP35 and VP24, which blocks the functions of Interferons.
The dendritic cells mentioned above are also severely impaired during infection. The Interferon discussed would normally help the dendritic cells to act as the pep rally for the troops (specifically those T cells). But by interfering with Interferon production, Ebola forces the dendritic cell to communicate a message of “No problem here” instead of “Danger! Danger!”.
Interrupting all of these levels of the immune system creates a very deadly virus.