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Clinical information


1. How contagious is measles?

Measles is a highly contagious virus, much more contagious than the common cold and even more contagious than other outbreaks like smallpox or Ebola.1 Measles is potentially transmissible even after brief exposures and at distances up to 30 meters.2 Herd immunity occurs when enough people in a group are immune to a virus or infection that it is hard for the virus to spread. This is also known as community or population immunity.3

The CDC standard of a 95% vaccination rate would result in less than one person being at risk of a measles infection. Below a vaccination rate of 95%, one person with measles can infect up to 18 people (if the vaccination rate is 0%).1

In some Texas counties, the MMR vaccination rate has reached a nadir of 67%. At this low vaccination rate, one person with measles can spread the virus to five people.1

2. What are the risks and complications if someone develops measles?

Based on historical data, the CDC has estimated that approximately 1 in 4 cases of measles in the U.S. result in hospitalization, and 1 in 1,000 cases results in death.4 Additionally, with increased age, there was a higher risk of complications such as encephalitis, pneumonia, and keratoconjunctivitis.4 Other complications include blindness, severe diarrhea and related dehydration, ear infections, and severe breathing problems.5

3. What are complications associated with pregnancy?

Measles can cause premature birth and low birth weight if a woman contracts measles while pregnant.5 Complications are most common in children under 5, adults over the age of 30, and children who are malnourished or have a compromised immune system.5 Most measles deaths occur from disease-related complications.

4. How do dermatologists and other clinicians recognize measles?

The measles virus is usually transmitted from a respiratory illness usually resulting in at least one of the three “Cs” (cough, conjunctivitis and coryzal symptoms) and followed by a characteristic maculopapular rash.

Early symptoms, 4-7 days:

  • Runny nose and/or sore throat (coryza)

  • Cough

  • Red and watery eyes (conjunctivitis)

  • Small white spots inside the cheeks (Koplik spots)5,6

Later symptoms, 7-18 days after exposure:

  • Rash

    • The rash usually begins as flat red spots that appear on the face and upper neck, before spreading across the trunk, arms, legs and feet over about 3 days.6 The rash usually resolves after 5-6 days.5,7 Notably, the measles rash typically spares the palms and the soles.

    • Flat red macules may coalesce as the rash spreads across the body.

  • High fevers (above 104 Fahrenheit / 40 Celsius) may be associated with the onset of rash.


Examples of Koplik spots

Image for AAD Measles of early syptoms

Figure 1. White-blue papules on the buccal mucosa (Koplik spots) of a patient during the prodromal phase of measles. Source: CDC.

Image for AAD Measles of Koplik spots

Figure 2. White papules on an erythematous base on the buccal mucosa (Koplik spots) of a patient during the prodromal phase (3 days after exposure). Source: CDC.

Image for AAD Measles of Koplik spots

Figure 3. Erythematous papules on the palate (Koplik spots) of a patient during the prodromal phase (3 days after exposure). Source: CDC.


Examples of measles rash during the eruptive phase

Image for AAD Measles of a child with measles symptoms

Figure 4. Numerous fine papules on the forehead of a child with measles. Source: CDC.

Image for AAD Measles of a child with measles symptoms

Figure 5. Scattered dusky macules and papules on the forehead and cheeks of a child with measles. Source: CDC.

Image of child with measles

Figure 6. Close-up of the characteristic maculopapular rash associated with measles on the cheek of a child. Source: CDC.

Image for AAD Measles of a child with measles symptoms

Figure 7. Erythematous macules and papules on the forehead of a child with measles. Source: CDC.

Image of child with measles

Figure 8. Faint exanthem comprising of erythematous macules and papules on the forehead of a child with measles. Source: WHO.

Image for AAD Measles of a child with measles symptoms

Figure 9. Confluent erythematous macules and patches on the face, neck, trunk, and extremities of a child with measles. Source: CDC.


Examples of measles rash during the convalescence phase

Image for AAD Measles of a child with measles symptoms

Figure 10. Desquamation on the face, chest, and arms of a child during the third convalescence phase of measles. Source: CDC.

Image for AAD Measles of a child with measles symptoms

Figure 11. Desquamation on the back of a child during the third convalescence phase of measles. Source: CDC.


References
  1. As the Texas outbreak grows, how contagious is measles, really? NPR. https://www.npr.org/sections/shots-health-news/2025/02/28/nx-s1-5312088/measles-texas-outbreak-contagious-spread. Updated 02/28/2025. Accessed 03/04/2025.

  2. Measles Investigative Guidelines Oregon Health Authority. https://www.oregon.gov/oha/ph/diseasesconditions/communicabledisease/reportingcommunicabledisease/reportingguidelines/documents/measles.pdf. Updated 12/2025. Accessed 03/13/2025.

  3. Herd Immunity. Cleveland Clinic. https://my.clevelandclinic.org/health/articles/22599-herd-immunity. Updated 03/16/2022. Accessed 03/03/2025.

  4. Chovatiya R, Silverberg JI. Inpatient morbidity and mortality of measles in the United States. PLoS One. 2020;15(4):e0231329.

  5. Measles. WHO. https://www.who.int/news-room/fact-sheets/detail/measles. Updated 11/14/2024. Accessed 03/03/2025.

  6. Measles Symptoms and Complications. CDC. https://www.cdc.gov/measles/signs-symptoms/index.html. Updated 05/09/2024. Accessed 03/04/2025.

  7. Measles. DermNet. https://dermnetnz.org/topics/measles. Updated 10/2020. Accessed 03/03/2024.

  8. Photos of Measles. CDC. https://www.cdc.gov/measles/signs-symptoms/photos.html. Updated 03/23/2024. Accessed 03/05/2025.

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