DHEA protects rats
A medical journal article (J Med Virol. 1992 Nov;38(3):159-66) entitled, "Dehydroepiandrosterone protects mice inoculated with West Nile virus and exposed to cold stress," discusses the protective effects of DHEA in mice following innoculation with the West Nile virus. Of course mice and people are different things, but it was interesting that 83% died when stressed but DHEA produced a "significant" reduction in death from the virus. The virus blood level was also significantly reduced in DHEA injected mice.
DHEA is a hormone you can purchase at most drug stores.