A measles outbreak in Knox County, Ohio, grew to 14 cases this week, with the state's overall count in double digits across four counties.
How many cases are there in Ohio?
The Ohio Department of Health confirmed 20 measles cases in the state as of Thursday: 11 in Ashtabula County near Cleveland, seven in Knox County and one each in Allen and Holmes counties.
Ohio is not including non-residents in its count, a state health department spokesperson told The Associated Press. The Knox County outbreak in east-central Ohio has infected a total 14 people, according to a news release from the county health department, but seven of them do not live in Ohio. A measles outbreak in central Ohio sickened 85 in 2022.
The outbreak in Ashtabula County started with an unvaccinated adult who had interacted with someone who had traveled internationally.
Other states with active outbreaks — defined as three or more cases — include New Mexico, Indiana, Kansas and Oklahoma. The virus has been spreading in undervaccinated communities. The third person who died was an adult in New Mexico who was not vaccinated.
The multi-state outbreak confirms health experts' fears that the virus will take hold in other U.S. communities with low vaccination rates and that the spread could stretch on for a year. The World Health Organization has said cases in Mexico are linked to the Texas outbreak.
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 has been considered eliminated from the U.S. since 2000.
Where else is measles showing up in the U.S.?
Measles cases also have been reported in Alaska, California, Colorado, Florida, Georgia, Hawaii, Kentucky, Maryland, Michigan, Minnesota, New Jersey, New York, Pennsylvania, Rhode Island, Tennessee, Vermont, and Washington.
The U.S. Centers for Disease Control and Prevention defines an outbreak as three or more related cases. The agency counted six clusters that qualified as outbreaks in 2025 as of Friday.
In the U.S., cases and outbreaks are generally 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 607.
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 health experts don't always recommend this route and insurance coverage can vary.
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, blindness, brain swelling and death.
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.
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.
The U.S. saw a rise in measles cases in 2024, including an outbreak in Chicago that sickened more than 60.