Generally, young children and seniors are the age groups most severely affected by influenza and other viral infections, said Dr. Sean O'Leary, an associate professor of pediatric infectious disease at the University of Colorado School of Medicine. "We certainly see more impact from viruses in people who have some kind of underlying chronic disease," O'Leary said. "Children tend to do better with these diseases than older adults because, in general, they tend to be a healthier population."