A new outbreak of measles has taken hold in Texas beginning at the end of January, when two cases were diagnosed in Harris County. The cases were the first in that state since 2023. Now, a little more than a month later, the number of measles cases has increased exponentially to 124, as of Tuesday.

Harris County includes Houston, which has a population of over 2 million. So a hundred or so cases of measles wouldn’t seem overwhelming to the average observer — except for a fairly well-known quirk of the viral infection: It spreads like wildfire.

Here in Maryland, some 1,500 miles away, it might be prudent to check your vaccine status — measles infection is preventable via immunization, according to the Maryland Department of Health.

Below are five things to know about measles.

Measles can be deadly, especially for children

Texas health officials said Tuesday that a school-age child had died of measles. The child, who was unvaccinated, was hospitalized last week in Lubbock. The Texas Department of State Health Services said most of the current infections are in children.

“Measles is a highly contagious respiratory illness, which can cause life-threatening illness to anyone who is not protected against the virus. During a measles outbreak, about one in five people who get sick will need hospital care and one in 20 will develop pneumonia,” Texas DSHS said in a news release.

For measles vaccine, two is better than one

Few vaccines, including the measles vaccine, are absolutely foolproof. And there have been reported breakthrough infections in the Texas outbreak — meaning some who were infected were indeed vaccinated; however, their illness was mild and less likely to infect others. One dose of the measles vaccine offers 93% protection against the virus, according to the Centers for Disease Control and Prevention. A second dose bumps it to 97%. Maryland schools require students from kindergarten to 12th grade to be immunized against measles with two doses of the MMR vaccine that also includes mumps and rubella. As of the 2023-24 school year, the CDC estimated 96.6% of Maryland kindergartners had received both doses.

Some people might need a booster shot

As children, millennials and Gen X’ers might have only received a single dose of the measles vaccine in the years prior to the CDC’s updated recommendation for a double dose that came in 1989. People born in 1958 and up to about 1988 might need to check with a physician about their immunity levels. (Those born in 1957 and before that likely have been exposed to measles and are generally considered immune.)

Measles was declared eliminated in 2000 in the U.S.

Because of a successful vaccination program, U.S. health officials declared measles eliminated in 2000.

“This meant the absence of the continuous spread of disease was greater than 12 months,” according to the CDC. It did not last. In 2024, the health agency said declines in vaccination had “increased the risk of measles outbreaks worldwide, including in the United States. Measles cases continue to be brought into the United States by travelers who are infected while in other countries. As a result, domestic measles outbreaks have been reported in most years.”

Maryland is not immune to outbreaks

In 2019, there were five cases of measles in Maryland, including four in the Baltimore area, according to the Baltimore City Health Department. There were no additional outbreaks of measles in the state until 2023, when one case was confirmed in Montgomery County. Another case was identified in 2024 in an international traveler. So far, according to the Maryland Department of Health, there have been no confirmed measles cases in Maryland in 2025.

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