What is one of the cardinal symptoms of measles?

Koplik spots are a key indicator of measles and are considered one of the hallmark symptoms of the disease. These tiny, white, ulcer-like spots, often described as resembling grains of salt or sand, appear on the mucous membranes, typically on the inner lining of the cheeks and are usually present before the onset of the measles rash. Their presence is highly specific to measles and can aid in early diagnosis, particularly when there may be confusion with other illnesses exhibiting similar symptoms.

In addition to Koplik spots, measles is often associated with a classic triad of symptoms: initial fever, a persistent cough, and conjunctivitis, which can occur later in the disease course. However, Koplik spots stand out as a distinctive early symptom, helping clinicians differentiate measles from other viral infections. Foul-smelling stool, while it may occur in various gastrointestinal conditions, is not related to measles. Bilateral conjunctivitis can happen with several viral infections but is less specific to measles compared to the presence of Koplik spots.