RHINOVIRUS INFECTIONS IN A STUDENT POPULATION: ISOLATION OF FIVE NEW SEROTYPES

During a 3-year study of acute respiratory tract illness in college and medical students, 322 specimens were obtained from students with symptoms of the common cold. One-hundred eighteen rhinoviruses (37 %) were isolated; 29 distinct serotypes were identified among the isolates. Eight new serotypes were established in the course of the study, three of which are already included in the recent listing of types to which numbers have been assigned by the Collaborative Rhinovirus Program; 5 are new types beyond the 55 already included in the numbering system. In addition, 6 strains of herpes simplex virus, 2 strains of adenovirus type 3, and 2 strains of parainfiuenza type 1 were also isolated. No pathognomonic symptom or combination of symptoms emerged to distinguish rhinovirus infections from each other or from other mild URIs, although the two students from whom adenovirus type 3 were isolated both had exudative pharyngitis with cervical adenopathy, conjunctivitis and high fever. Between September of 1964 and May of 1965, an Intensive study of URIs in Baylor medical students was performed. A total of 257 colds were reported during this period by 165 students, representing an attack rate of 1.6 colds per student. Based on virus isolations alone, 43 % of these infections were associated with 18 different rhinovirus serotypes. Two peaks of illness occurred during the year, in October and January, associated with the highest rhinovirus isolation rates. Most of the October infections were due to a large outbreak caused by rhinovirus 17. Rhinovirus infections appear to induce at least partial immunity to reinfection with the same serotype. Of 64 paired sera collected from students with acute URIs, 62% showed a serum antibody titer rise. This antibody appeared to be homotypic. In one student with 5 different rhinovirus infections observed during a one-year period, no anamnestic antibody response was noted. In addition, in 23 students with 2 or more illnesses, the same serotype was never isolated from separate illnesses in the same student. No specific pattern emerged for the occurrence of rhinoviruses in the population. Some serotypes were found throughout the study period, while others caused small outbreaks at a given time and then disappeared. The ultimate control of these infections represents a major medical challenge.