A child presents with fever, cough, coryza (runny nose), conjunctivitis, and small white spots on the buccal mucosa opposite the lower molars. What is the most likely diagnosis?

Koplik's spots — small, blue-white spots on the buccal mucosa opposite the first and second lower molars — are pathognomonic for measles (rubeola). They appear 1–2 days before the characteristic maculopapular skin rash. The prodrome of measles is characterized by the '3 Cs': Cough, Coryza (nasal discharge), and Conjunctivitis, accompanied by high fever. Measles is caused by the measles paramyxovirus and is transmitted by airborne droplet nuclei. In the dental setting, suspected measles patients should be managed with airborne precautions (N95 respirator), and elective dental treatment should be deferred.