Texas, Oklahoma and New Mexico reported new measles cases this week, with the outbreak expanding for the first time into central Texas.

Already, the U.S. has more measles cases this year than in all of 2024, the U.S. Centers for Disease Control and Prevention has said. Other states with outbreaks — defined as three or more cases — include New Mexico, Kansas, Ohio and Oklahoma. Since February, two unvaccinated people have died from measles-related causes.

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 said last week that 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.

Here’s what else you need to know about measles in the U.S.

How Many Measles Cases Are There in Texas and New Mexico?

Texas’ outbreak began two months ago. State health officials said Tuesday there were 22 new cases of measles since Friday, bringing the total to 422 across 19 counties — most in West Texas. Erath and Brown counties, in the central part of the state, logged their first cases. Forty-two people have been hospitalized since the outbreak began.

New Mexico announced four new cases Tuesday, bringing the state’s total to 48. New Mexico health officials say the cases are linked to Texas’ outbreak based on genetic testing. Most are in Lea County, where two people have been hospitalized, and two are in Eddy County.

A school-age child died of measles in Texas in late February, and New Mexico reported its first measles-related death in an adult on March 6.

How Many Cases Are There in Kansas?

Kansas has 24 cases in six counties in the southwest part of the state as of Wednesday. Kiowa and Stevens counties have six cases each, while Grant, Morton, Haskell and Gray counties have five or fewer.

The state’s first reported case, identified in Stevens County on March 13, is linked to the Texas and New Mexico outbreaks based on genetic testing, a state health department spokesperson said. But health officials have not determined how the person was exposed.

How Many Cases Are There in Oklahoma?

Oklahoma logged one new measles case Tuesday — for a total of eight confirmed and two probable cases. The first two probable cases were “associated” with the West Texas and New Mexico outbreaks, the state health department said.

A state health department spokesperson said measles exposures were confirmed in Tulsa and Rogers counties, but wouldn’t say which counties had cases.

How Many Cases Are There in Ohio?

Ohio reported one new measles case Thursday in west-central Allen County. Last week, there were 10 in Ashtabula County in the northeast corner of the state. The first case was in an unvaccinated adult who had interacted with someone who had traveled internationally.

In central Ohio, Knox County officials reported two new measles cases in international visitors, for three cases in international visitors total. Those cases are not included in the state’s official count becuase they are not in Ohio residents. A measles outbreak in central Ohio sickened 85 in 2022.

Where Else Is Measles Showing Up in the U.S.?

Measles cases also have been reported in Alaska, California, Colorado, Florida, Georgia, 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 five 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.

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.

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AP Science Writer Laura Ungar contributed to this report.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.