Virus	Estimated annual proportion of cases
Rhinoviruses	30–50%
Coronaviruses	10–15%
Influenza viruses	5–15%
Respiratory syncytial virus	5%
Parainfluenza viruses	5%
Adenoviruses	<5%
Enteroviruses	<5%
Metapneumovirus	Unknown
Unknown	20–30%