A library of nasopharyngeal specimens collected biweekly from 125 family groups, approximately 500 persons, over a three-year period, and serum specimens collected at four-month intervals over the same three-year period, will be used for rhinovirus studies. We will study patterns of rhinovirus shedding and antibody response in the family groups under surveillance and patterns of prevalent serotypes with time. We will study antigenic drift among rhinoviruses by characterizing variants of known types and the study of intertypes, isolates with antigenic character of two related types, but not identical to either. We will study immune response in infected persons to determine the effect of pre-existing antibody on disease, and to determine the extent of heterotypic response to related viruses. We will search for dual rhinovirus infections, recently shown to occur in 3.2% of 135 infections examined, to determine the extent to which these occur. During the course of these investigations, we will look for ways to improve methodology for rhinovirus isolation, (look for more sensitive cell culture system) and detection of antibody (ELISA testing).