<unk> s <unk> s) are infectious diseases involving the respiratory<unk> . An infection of this type usually is further classified as an upper<unk>  (URI or URTI) or a lower<unk>  (LRI or LRTI). Lower respiratory infections, such as pneumonia, tend to be far more severe than upper respiratory infections, such as the common cold.
Respiratory tract infection
Lower respiratory tract infection
Upper respiratory tract infection
Respiratory disease
Mouth infection
Pulmonary aspiration
Smoke inhalation
Airway obstruction