Viruses that cause hemorrhagic fevers and are category A agents in the CDC classification are the Ebola, Marburg, Lassa, Junin, Machupo, Guanarito, and Sabia viruses [70] . They are widely distributed in nature. Humans are highly susceptible [71] . Many are spread by airborne transmission, and although humans are not natural hosts for any of the viral hemorrhagic fevers, infected humans can spread the disease from person-to-person [12] .