Protein fragments, called amyloid fibrils, in human semen significantly increase Ebola virus infection and protect the virus against harsh environmental conditions such as heat and dehydration. Follow-up studies from the 2014 epidemic found that men can harbor the virus in their semen for at least 2.5 years, with the potential to transmit the virus sexually during that time. Targeting amyloids in semen may prevent a sexually transmitted spread of the Ebola virus.