Koplik spots — small white lesions with a red halo on the buccal mucosa — are pathognomonic for which viral infection?

Koplik spots are pathognomonic for measles (rubeola), caused by the measles morbillivirus (a paramyxovirus). They appear as small, white-gray spots with erythematous halos on the buccal mucosa, typically opposite the lower molars, 1-2 days before the characteristic measles skin rash (morbilliform rash) appears. They are often described as grains of sand or salt on a red background. Koplik spots represent foci of viral cytopathic effect on the buccal mucosa and represent an important early clinical diagnostic sign. They disappear as the skin rash emerges. Neither HIV nor rotavirus produces Koplik spots. In the dental setting, identifying Koplik spots allows recognition of a highly contagious (airborne) infectious disease requiring immediate isolation.