After being eliminated in the United States in 2000, measles has been slowly creeping back and is now making headlines.
As of April 2025, there have been 800 confirmed cases of measles in 25 states in the U.S., reports the Centers for Disease Control and Prevention (CDC), including the first confirmed measles case in Illinois, according to the Illinois Department of Public Health (IDPH).
Highly contagious
Measles, an airborne disease caused by a virus known as rubeola, is more contagious than almost any other infectious disease. The virus spreads through droplets when an infected person breathes, coughs, sneezes, laughs, talks or sings.
“It’s important for parents — and all adults — to not underestimate this disease,” said Jennifer Grant, MD, an infectious disease specialist with Endeavor Health Medical Group. “It can spread easily and incredibly fast,” she added.
Up to 9 in 10 people who lack immunity to measles and are close to an infected person will become infected, stated the National Foundation for Infectious Diseases.
Symptoms
Measles first infects the respiratory tract and then spreads throughout the body. Symptoms may include a fever, cough, runny nose, mouth sores (tiny, white “Koplik spots”), red eyes, and sore throat. A few days after initial symptoms, a red, blotchy rash may appear on the face and hairline, and spread to the neck, chest, back, arms, legs and feet. The illness usually lasts for 7-10 days.
Besides being highly contagious, what makes it so dangerous is that measles can cause severe disease, complications (e.g., pneumonia, brain swelling), and even death.
Measles can be serious for all ages, but children younger than 5, adults older than 20, pregnant women, and immunocompromised people are more likely to suffer from measles complications. Adults may also have stronger symptoms with a longer recovery period and a higher chance of complications.
Protection
The best defense against measles is vaccination. A person who is unvaccinated or not immune has a 90% chance of contracting measles when exposed.
The measles, mumps and rubella vaccine (MMR) vaccine comes in two doses, given at ages 12-15 months and 4-6 years. Learn more about measles in children.
What should adults know about vaccination?
Most adults in the United States received two doses of the MMR vaccine as children. If you are one of them, you should be protected for life. If you only got one dose as a child, you should still be protected, as well as if you were born before 1957, as it’s assumed you have natural immunity.
According to the CDC, two doses of measles vaccine are about 97% effective at preventing measles if exposed to the virus, while one dose is about 93% effective.
Some adults, however, may consider getting revaccinated with at least one dose of the current MMR vaccine, especially those who work in colleges or healthcare settings, travel internationally, or were vaccinated between 1957-1968 (as they may have received a less effective version of the vaccine).
Unfortunately, most individuals who are immunocompromised are unable to get the MMR vaccine, making it especially important to understand your immune status if one of your loved ones is has a condition that suppresses their immune system.
If you aren’t sure about your immunity to measles, talk with your doctor about your vaccination record. In Illinois, you can try to verify your vaccine status using a tool called Vax Verify. Or, your physician can order a blood test to see if you have immunity.
“But, it may be simpler to just get the vaccine. There is no harm in getting another dose of MMR vaccine if you are already immune, and aren’t pregnant or immunocompromised,” said Dr. Grant.
Measles doesn’t seem to be going away anytime soon. The first three months of 2025 have seen more measles cases reported than in all of 2024.
“The most important thing you can do to protect yourself, your kids, and your community from the disease is to stay up to date on vaccination so the disease can be eliminated once and for all,” said Dr. Grant.
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