Never Seen Measles? 5 Things to Know

Andrew T. Pavia, MD


May 02, 2019

In This Article

3. The Most Important Diagnostic Tool Is Your H&P

To diagnose measles quickly enough to allow quarantine, contact tracing, vaccination of susceptible contacts, and other public health interventions, you need to recognize and diagnose the disease clinically. This requires a good history and physical exam. Measles is readily recognizable by its clinical features.

History can aid in identifying a patient's susceptibility (eg, vaccination status) and possible exposure to measles, such as travel to areas of ongoing transmission. The Centers for Disease Control and Prevention (CDC) maintains a list of confirmed measles cases and the states in which they occurred, updated weekly. A careful history of disease progression and symptoms is critical.

After an incubation period of 8-12 days after exposure, the prodromal symptoms begin with fever, cough, coryza, and conjunctivitis (the "three Cs").[4,5] During this period, Koplik spots—bluish-white lesions on a red base—may appear on the buccal mucosa, most often opposite the molars.

Figure 1. Koplik spots. Courtesy of CDC.

If present, Koplik spots are virtually pathognomonic. Fever increases over 2-4 days, as high as 104°F, and the patient is usually quite ill-appearing. Photophobia can be prominent.

After 2-4 days, the rash appears on the forehead or back of the head and spreads downward to the trunk and extremities over the next 3 days.

Figure 2. Measles rash.

The rash is red and maculopapular, often with raised areas. The rash can become confluent on the face or torso before fading in the same head-to-toe pattern. The rash can be harder to recognize in very dark-skinned patients, although it is often obvious to a child's parent Fever typically peaks 2-3 days after rash onset. Persistent or recurrent fever may signal bacterial infection. The rash may be absent in immunocompromised patients.

People with measles are contagious from the onset of the prodrome until 48 hours after the rash appears.


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