In response to COVID-19 and other viral, airborne respiratory infections, experts have recommended increased ventilation in hospitals, nursing homes, schools, and other public buildings. However, new research from Stanford University suggests that excess ventilation can reduce relative humidity in a way that could counteract public health interventions targeting airborne viral infections. This work may help explain why, in many regions of the world, more people tend to get sick with airborne viruses in winter, when heating systems dry out indoor air. Previous research led by Richard Zare revealed that