Michigan reports first confirmed measles outbreak since 2019

Seven cases have been confirmed in Michigan this year, say health officials.

Michigan is reporting the state’s first measles outbreak since 2019, defined as at least three or more related cases, according to the Michigan Department of Health and Human Services (MDHHS).

Three cases were confirmed in Montcalm County, according to a MDHHS statement.

Almost 25% of children under 3 years of age in Montcalm County have not received their first dose of the measles, mumps and rubella (MMR) vaccine, according to the MDHHS vaccination data. The state is reporting a total of seven cases so far this year, including those infected in the outbreak.

The Centers for Disease Control and Prevention (CDC) has separately confirmed at least five other states with measles outbreaks, including Texas, New Mexico, Ohio, Kansas and Indiana.

Nationwide, there are over 700 measles cases in at least 24 states. That's the highest number since 2019, which saw 1,274 cases. Texas makes up the bulk of those cases with over 560 infections, including two deaths among unvaccinated school-aged children.

Measles is one of the most contagious diseases known to humans. Just one infected patient can spread measles to up to nine out of 10 susceptible close contacts, according to the CDC.

Health officials have been urging anyone who isn’t vaccinated to receive the MMR vaccine.

The CDC currently recommends people receive two vaccine doses, the first at ages 12 to 15 months and the second between 4 and 6 years old. One dose is 93% effective and two doses are 97% effective at preventing measles. Most vaccinated adults don’t need a booster.

In the decade before the measles vaccine became available in 1963, an estimated three to four million people were infected every year, according to the CDC, with between 400 and 500 deaths.

ABC News' Mary Kekatos contributed to this report.