In an influenza challenge study reported in 1998 in which normal human volunteers were experimentally infected with a seasonal influenza A (H1N1 Texas/36/91) virus, Hayden et al. found that both IL-6 and IFN-alpha levels in nasal lavage fluids peaked early in the course of infection and correlated directly with viral titers, temperature, mucus production, and symptom scores [8]. Here, IL6 is linked to infection.