Upper respiratory tract infections (URI) are illnesses caused by an acute infection which involves the upper respiratory tract including the nose, sinuses, pharynx or larynx. This commonly includes nasal obstruction, sore throat, tonsillitis, pharyngitis, laryngitis, sinusitis, otitis media, and the common cold. Acute bacterial rhinosinusitis (ABRS) is an infection of both your nasal cavity and sinuses. It is caused by bacteria. It’s most often caused by the bacteria Streptococcus pneumoniae, Moraxella catarrhalis or Haemophilus influenzae. It often starts in the nasal cavity and spreads into your sinuses.