Stringy particles of Ebola virus (blue) bud from a chronically infected cell (yellow-green) in this colorized, scanning electron micrograph. NIAID/Science Source hide caption

itoggle caption NIAID/Science Source

Several countries, including Australia, Japan and Great Britain, already encourage blood donations from some gay men. Kevin Curtis/Getty Images/Science Photo Library hide caption

itoggle caption Kevin Curtis/Getty Images/Science Photo Library