A 12-month-old infant shows symptoms of fever and a rash with white spots in the mouth. Which communicable disease should the nurse suspect?

The symptoms described—a fever accompanied by a rash that features white spots in the mouth—are characteristic of rubeola, commonly known as measles. Measles is known for presenting with a prodromal phase that includes high fever and respiratory symptoms, followed by a distinctive rash that typically starts on the face and spreads downwards.

A hallmark of measles is the appearance of Koplik spots, which are small, white lesions found in the oral mucosa, often appearing 1-2 days before the onset of the rash. This combination of oral lesions and the progression of the rash aligns closely with the clinical presentation of rubeola.

In contrast, rubella (commonly known as German measles) typically presents with a milder rash and does not include Koplik spots. Pertussis (whooping cough) is characterized by severe coughing spells and does not present with a rash. Varicella (chickenpox) features a vesicular rash rather than a maculopapular rash, and the spots in the mouth are not typical of this illness. Therefore, given the specific symptoms of fever, rash, and oral lesions, the diagnosis of rubeola is the most likely and appropriate conclusion.