A preschool child with fever, cough, coryza, conjunctivitis, and morbilliform rash in an unimmunized setting is most likely diagnosed as which disease?

• A. Rubella
• B. Measles
• C. Roseola
• D. Varicella

Answer: (B)

The key idea is recognizing the classic presentation of measles. The combination of fever with cough, coryza, and conjunctivitis—the three C’s—along with a morbilliform (maculopapular) rash is highly characteristic of measles. In measles, fever is typically prominent and the rash begins on the face and hairline and spreads downward. Koplik spots on the oral mucosa can be a helpful, pathognomonic clue, though they’re not always seen.

In an unimmunized child, this pattern is especially suggestive because vaccination dramatically reduces measles incidence, so the appearance of this constellation strongly points to measles rather than other rash illnesses.

Why the others fit less well: rubella can cause a milder fever and rash but usually features prominent lymphadenopathy and is less likely to have the pronounced conjunctivitis and the “three C’s” combination; roseola starts with high fever that breaks before a rash appears and does not typically include prominent cough or conjunctivitis; varicella presents with vesicular lesions in various stages of healing rather than a morbilliform rash.

So, the fever with the 3 C’s and a morbilliform rash in an unimmunized preschooler best fits measles.