A nurse is planning an in-service about communicable diseases for staff members. Which of the following diseases should the nurse identify as causing Koplik spots?

A. Diphtheria: Diphtheria, caused by Corynebacterium diphtheriae, primarily affects the upper respiratory tract and is characterized by a thick pseudomembrane in the throat and systemic toxin effects. Koplik spots are not associated with this bacterial infection. B. Poliomyelitis: Poliomyelitis is caused by the poliovirus and primarily affects motor neurons, potentially leading to paralysis. Oral mucosal manifestations such as Koplik spots are not present in this viral illness. C. Measles (rubeola): Measles, caused by the measles virus, is characterized by prodromal fever, cough, coryza, conjunctivitis, and the appearance of Koplik spots on the buccal mucosa. These small, white or bluish-white lesions with a red base are pathognomonic for measles and appear 1–2 days before the skin rash. D. Fifth disease (erythema infectiosum): Fifth disease, caused by parvovirus B19, presents with a “slapped cheek” rash and mild systemic symptoms. Koplik spots are not a feature of this illness.