Measles vs. Rubella: How to Tell the Difference? Both measles and rubella present with fever and rash, but there are key differences that can help you distinguish them: ✅ Timing of Rash Onset: Measles: Rash appears after the fever has already started. Rubella: Rash develops along with the fever. ✅ Rash Progression: Measles: Starts behind the ears (retroauricular) and spreads downward (cephalocaudally). Rubella: Begins on both cheeks (bilateral malar area) before spreading. ✅ Oral Mucosal Signs: