Characterization and Classification of ECHO 28-Rhinovirus-Coryzavirus Agents

Thirty-five coryzavirus strains were recovered from cases of common cold in adults and from “colds” (upper respiratory illness), croup, bronchitis and bronchopneumonia in children. Two additional viruses were recovered from clinically well persons. These viruses were divided into 20 distinct serotypes based on tests with specific guinea pig antisera. Nineteen of the 20 types grew only in human cell cultures (H) while a single type (30) propagated also in grivet monkey kidney cells (M). None of the coryzavirus strains was related immunologically to any of the rhinoviruses, or to the ECHO, Coxsackie A or B, or reoviruses. The coryzaviruses shared properties with the ECHO 28 and rhinoviruses which provided a basis for the designation of an ECHO 28-rhinovirus-coryzavirus (ERC) group and for differentiating them from the remaining ECHO and Cox-sackie A and B viruses. The ERC agents share with ECHO-Coxsackie A and B agents the properties of small size, RNA type, and ether stability, but differ from them in acid lability and in infection of the respiratory tract of man in contrast to the usual habitat in the gut of the ECHO and Coxsackie agents. The H strains of coryzavirus and rhinovirus also differed from the ECHO 1-27 and Coxsackie viruses in their relative stability to heat. The M strains of rhinovirus and coryzavirus and ECHO 28 were intermediate and showed highly variable heat stability properties. The exact position and nomenclature of the ERC viruses remain to be determined.