III. Myxoviruses: Parainfluenza

Abstract

The newly uncovered parainfluenza viruses are associated with a minimum of 6 to 19% of respiratory tract illness in children. Parainfluenza 1, 2, or 3 viruses may be found in mild rhinitis, pharyngitis, and bronchitis but the more severe parainfluenza 1 and 2 infections seem to be associated with the croup syndrome; the more severe parainfluenza 3 infection with bronchopneumonia; bronchiolitis; or croup. Parainfluenza 1 and 3 infections occur in all seasons in each year. A vast majority of adults have been infected at least once. A child or adult may be reinfected with the same agent but the presence of antibody prevents severe illness and higher levels seem to lessen the likelihood of infection. An antigenically potent vaccine could prevent, theoretically, much serious respiratory tract illness in children and, frequently administered, might even reduce the colds that result from reinfection.