A measles case has been reported in an adult in southern Illinois, joining several other nearby states, including Michigan, Indiana, Kansas, Missouri, Minnesota and Ohio. The outbreak in western Texas has now reached 624 cases, and Gaines County remains the epicenter of the outbreak there.
Measles is caused by a highly contagious virus that’s airborne and spreads easily when an infected person breathes, sneezes or coughs. It is preventable through vaccines, and had been considered eliminated from the U.S. since 2000.
Here’s what else you need to know about measles in the U.S.
What is an outbreak?
The U.S. Centers for Disease Control and Prevention defines an outbreak as three or more related cases. The agency counted seven clusters that qualified as outbreaks in 2025 as of last week.
In the U.S., cases and outbreaks are frequently traced to someone who caught the disease abroad. It can then spread, especially in communities with low vaccination rates. In 2019, the U.S. saw 1,274 cases and almost lost its status of having eliminated measles. So far in 2025, the CDC’s count is 712.
Do you need an MMR booster?
The best way to avoid measles is to get the measles, mumps and rubella (MMR) vaccine. The first shot is recommended for children between 12 and 15 months old and the second between 4 and 6 years old.
People at high risk for infection who got the shots many years ago may want to consider getting a booster if they live in an area with an outbreak, said Scott Weaver with the Global Virus Network, an international coalition. Those may include family members living with someone who has measles or those especially vulnerable to respiratory diseases because of underlying medical conditions.
Adults with “presumptive evidence of immunity” generally don’t need measles shots now, the CDC said. Criteria include written documentation of adequate vaccination earlier in life, lab confirmation of past infection or being born before 1957, when most people were likely to be infected naturally.
A doctor can order a lab test called an MMR titer to check your levels of measles antibodies, but experts don’t always recommend it and health insurance plans may not cover it.
Getting another MMR shot is harmless if there are concerns about waning immunity, the CDC says.
People who have documentation of receiving a live measles vaccine in the 1960s don’t need to be revaccinated, but people who were immunized before 1968 with an ineffective measles vaccine made from “killed” virus should be revaccinated with at least one dose, the agency said. That also includes people who don’t know which type they got.
What are the symptoms of measles?
Measles first infects the respiratory tract, then spreads throughout the body, causing a high fever, runny nose, cough, red, watery eyes and a rash.
The rash generally appears three to five days after the first symptoms, beginning as flat red spots on the face and then spreading downward to the neck, trunk, arms, legs and feet. When the rash appears, the fever may spike over 104 degrees Fahrenheit, according to the CDC.
Most kids will recover from measles, but infection can lead to dangerous complications such as pneumonia and blindness. Another serious complication of measles is acute encephalitis, or inflammation of the brain, which can result in permanent brain damage in one of every 1,000 cases. In the U.S., death from neurologic or respiratory complications of measles occurs in one to three of every 1,000 cases, University of Chicago Medicine reports.
How can you treat measles?
There’s no specific treatment for measles, so doctors generally try to alleviate symptoms, prevent complications and keep patients comfortable while monitoring for serious complications.
Why do vaccination rates matter?
In communities with high vaccination rates — above 95% — diseases like measles have a harder time spreading through communities. This is called “herd immunity.”
But childhood vaccination rates have declined nationwide since the pandemic, and more parents are claiming religious or personal conscience waivers to exempt their kids from required shots. Vaccination coverage among U.S. kindergartners fell from 95.2% during the 2019–2020 school year to 92.7% in the 2023–2024 school year, leaving approximately 280,000 kindergartners at risk during the 2023–2024 school year, the CDC reports.
The U.S. saw a rise in measles cases in 2024, including an outbreak in Chicago that sickened more than 60.
