Episode Details

Episode 190: Measles Basics

Future Dr. Kapur explained the basics of measles, including the pathophysiology, diagnosis and management of this disease. Dr. Schlaerth added information about SPPE and told interesting stories of measles. Dr. Arreaza explained some statistics and histed the episode.  

Written by Ashna Kapur MS4 Ross University School of Medicine. Comments by Katherine Schlaerth, MD, and Hector Arreaza, MD.

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Introduction.

According to the CDC, as of April 24, 2025, a total of 884 confirmed measles cases were reported by 30 states, including California, and notably Texas. This is already three times more cases than 2024. There are 3 confirmed deaths so far in the US. What is measles?

Measles is a disease that’s been around for centuries, nearly eradicated, yet still lingers in parts of the world due to declining vaccination rates. Let's refresh our knowledge about its epidemiology, clinical features, diagnosis, management, and most importantly — prevention.

Definition.

Measles, also known as rubeola, is an acute viral respiratory illness caused by the measles virus. It’s a single-stranded, negative-sense RNA virus belonging to the Paramyxoviridae family. It’s extremely contagious with a transmission rate of up to 90% among non-immune individuals when exposed to an infected person.

Epidemiology

Before the introduction of the measles vaccine in 1963, nearly every child got measles by the time they were 15 years old. With the introduction of vaccination, cases and deaths caused by measles significantly declined. For example, in 2018, over 140,000 deaths were reported in the whole world, mostly among children under the age of 5.

Measles is still a common disease in many countries, including in Europe, the Middle East, Asia, and Africa. Measles outbreaks have been reported recently in the UK, Israel, India, Thailand, Vietnam, Japan, Ukraine, the Philippines, and more recently in the US. So, let’s take prevention seriously to avoid the spread of this disease here at home and abroad. How do we get measles, Ashna?

Mode of Transmission:

● Air: Spread primarily through respiratory droplets.

● Surfaces: The virus remains viable on surfaces or in the air for up to 2 hours. (so, if a person with measles was in a room and you enter the same room within 2 hours, you may still get measles)

● Other people: Patients are contagious from 4 days before until 4 days after the rash appears.

Pathophysiology

The measles virus first infects the respiratory epithelium, replicates, and then disseminates to the lymphatic system.

It leads to transient but profound immunosuppression, which is why secondary infections are common. It affects the skin, respiratory tract, and sometimes the brain, leading to complications like pneumonia or encephalitis.

Clinical Presentation

The classic presentation of measles can be remembered in three C’s:

● Cough

● Coryza (runny nose)

● Conjunctivitis

Course of Disease (3 Phases):

1. Prodromal Phase (2-4 days)

○ High fever (can peak at 104°F or 40°C)

○ The 3 C’s

○ Koplik spots: Small white lesions on the buccal mucosa.

2. Exanthem Phase

○ Maculopapular rash begins on the face (especially around the hairline), then spreads from head to toe. The rash typically combines into 1 big mass as it spreads, and the fever often p