MYXOVIRUSES ASSOCIATED WITH ACUTE LARYNGOTRACHEOBRONCHITIS IN TORONTO, 1962-63.

Between November 1962 and March 1963, myxoviruses were isolated from 95 of 224 children (40.5%), most of whom were aged less than three years, who were admitted to The Hospital for Sick Children, Toronto, with acute laryngotracheobronchitis (tracheitis or croup). Viral isolates included 87 strains of Parainfluenza-1, five of Parainfluenza-3, and three of Influenza A2. An epidemic of Influenza A2 afflicted Toronto during March 1963, at which time this virus was isolated from tracheitis patients.Myxoviruses were isolated from nasopharyngeal secretions of 285 of 794 tracheitis patients between November 1960 and March 1963. Parainfluenza-1 virus was the dominant serotype, being found in 241 (30.0%) of subjects. Three peaks of Parainfluenza-1 virus isolations were observed in December 1960, March 1962 and November 1962, and this serotype has been isolated during all months except June and July. Although most of the 28 Parainfluenza-3 virus infections occurred between November and February, this strain has also been isolated during summer. Strains of Influenza A2 and Influenza B viruses have been isolated from tracheitis patients during epidemics of influenza in Toronto due to these agents.