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What to know about measles outbreak in the U.S.

Published March 7th, 2024

Measles cases are on the rise globally, despite the availability of a safe and effective vaccine that prevents the infection. In the U.K., where over 400 cases have been detected since October of 2023,1 the alarming surge has been deemed a “national incident.” As a result, the U.S. Centers for Disease Control (CDC) issued a warning for physicians to be on alert for measles cases.

Although measles has been eradicated in the U.S. through a robust vaccination program with the measles, mumps, rubella vaccine (MMR), small outbreaks have recently cropped up in 20 states. In 2023, there were 58 measles cases in the U.S. and as of February 29, there have already been 41 cases reported in 2024,2 including a recent outbreak in a Florida elementary school with at least 6 cases.3 The rise in cases is due to decreased MMR vaccination rates.4 In the U.S., measles cases are found in unvaccinated individuals, and outbreaks are often the result of a child catching the virus while travelling internationally and then spreading it locally.

At Private Health Management, we recommend that families follow the CDC guidelines for vaccination of their children to protect against measles, which includes 2 doses of the MMR vaccine. In addition, any adults who have not been vaccinated or have not already had the measles should get vaccinated. Here is what you need to know about the measles virus.

Measles can be serious
Common symptoms of measles infection are fever, cough, runny nose, irritated eyes, and rash, though some people experience more serious complications from measles infection. Children under 5 years old, adults over 20 years old, pregnant women, and those who are immunocompromised are at high risk for more severe disease.

Serious complications include:

  • Hospitalization
  • Pneumonia
  • Encephalitis (brain swelling) that can lead to deafness or intellectual disability
  • Pregnancy complications in unvaccinated mothers, including low birth weights and premature birth
  • Death

Measles is very contagious
Measles is one of the most contagious diseases — it is so infectious that 90% of people exposed to person with measles will catch it if they are not vaccinated.5 The measles virus can spread through the air when an infected person coughs or sneezes and the virus can linger in the air for up to two hours. It can also spread by touching contaminated surfaces and then touching the face, nose, or eyes. An infected person can spread the virus before they know they have measles — from four days before developing the measles rash through four days afterward.

Measles infections are preventable
The MMR vaccine is 93% effective against measles infection, provides long-term protection, and also protects against mumps and rubella infections. Common side effects of the vaccine include sore arm from the shot, redness around the injection site, fever, and a mild rash.6

The CDC recommends that all children get two doses of MMR vaccine starting with the first dose at 12–15 months of age, and the second dose at 4–6 years of age.7 Teenagers and adults who were not vaccinated as children should become up to date with their vaccinations. It is also important to be vaccinated if traveling internationally; the CDC has an online tool to help determine whether a person may need additional doses of vaccine before travelling.

People who are pregnant, have a weakened immune system, have a blood disorder, or have had an allergic reaction to a previous MMR vaccine, should talk with their healthcare provider before getting an MMR vaccine.7


  1. National Measles Standard Incident – measles epidemiology (from October 2023). GOV.UK
  2. Wong, C. Measles outbreaks cause alarm: what the data say. Nature (2024).
  3. Six cases of measles confirmed in an outbreak at a Florida elementary school. NBC News (2024).
  4. CDC. Measles Cases and Outbreaks. Centers for Disease Control and Prevention (2024).
  5. CDC. Measles is Easily Transmitted. Centers for Disease Control and Prevention (2020).
  6. Measles-Mumps-Rubella (MMR) Vaccine Information Statement | CDC. (2023).
  7. Measles, Mumps, and Rubella (MMR) Vaccination | CDC. (2023).

About the Authors

Tracy Arsenault, MS, PA-C

Managing Clinical Director, ClearCare

Tracy is a board-certified Physician Assistant with experience as a Physician Assistant in Cardiology, Cardiothoracic and Vascular surgery. In addition, she has extensive experience as an exercise physiologist and clinical research associate with focus in muscle and aging, endocrinology, and nuclear medicine.

Julie Nowicki, PhD

Health and Science Writer

Dr. Nowicki has a background in scientific research and education, with a focus on molecular genetics, and has extensive experience as a medical writer. At PHM, she writes a variety of scientific communications, including articles and educational materials that summarize complex medical information for patients.