Mouse studies are useful, but they don’t always translate to humans. Last year, however, a study revealed that a type of herpesvirus called cytomegalovirus (CMV), which infects 50 to 80 percent of all 40-year-olds, enhances the immune response to the influenza virus. Critically, the researchers behind the study achieved the same results in both mice and humans.

Scientists are now doing more than just analyzing the effects of a latent herpes infection; they’re actively enlisting the virus in the fight against cancer. Last summer, an international team announced that they engineered the herpesvirus that causes cold sores to instead attack cancer cells. The therapy, called T-VEC, worked wonders in a phase III clinical trial involving 436 patients afflicted with late stage melanoma.

“Patients given T-VEC at an early stage survived about 20 months longer than patients given a different type of treatment,” University of Louisville cancer researcher Jason Chesney reported. “For some, the therapy has lengthened their survival by years.”