CDC: Spike in measles cases poses threat to US elimination status

child with measles


A rapid rise in measles cases in the first months of 2024 threatens the United States' elimination status, a situation the nation hasn't faced since 2019, when prolonged outbreaks posed a similar problem, the Centers for Disease Control and Prevention (CDC) said today.

CDC scientists from the group spelled out the warning today in Morbidity and Mortality Weekly Report (MMWR). In their analysis of measles activity from January 1, 2020, to March 28, 2024, they said cases in the first quarter of 2024 have risen 17-fold compared to the mean first-quarter average from 2020 to 2023.

As of the March 28 data cutoff, 97 cases had been reported to the CDC. In its latest update, which includes infections reported through April 4, the CDC confirmed 113 cases from 18 jurisdictions. Of 20 outbreaks involving 3 or more cases reported since 2020, 7 have occurred in 2024.

Maintaining measles elimination status—which helps reduce cases, deaths, and costs—means that no outbreaks have persisted for 12 months or more in a setting where the surveillance system is working well. 

The last threat to US elimination status occurred in 2019, which saw two prolonged outbreaks in undervaccinated communities in New York City and elsewhere in New York state.

More steps needed to maintain elimination

Because of the brisk pace in activity in 2024 so far, more activities are needed to increase measles, mumps, and rubella (MMR) vaccine coverage, especially in close-knit and undervaccinated communities, the CDC said. It said other steps are also needed to maintain measles elimination. "These activities include encouraging vaccination before international travel and rapidly investigating suspected measles cases."

Most cases are still considered imported; however, of those, 61% were in US residents who were eligible for vaccination but were unvaccinated or had an unknown vaccination status. 

The CDC is also seeing a shift this year in the overseas regions where people were likely exposed. During the study period, the two most common World Health Organization (WHO) regions were the Eastern Mediterranean (Middle East) and Africa. However, six of the 2024 cases were reported to have originated in the European and Southeast Asia regions—a 50% increase from earlier in the study period.

Along with undervaccination in some of the US population, a global gap in measles vaccination is also fueling the rise in cases, the CDC said. According to global estimates, first-dose coverage declined from 86% in 2019 to 83% in 2022, leaving nearly 22 million children younger than 1 year vulnerable to the virus.

Michigan reports another case as Chicago outbreak grows

In related developments, the Detroit Health Department yesterday reported a measles case involving a 4-year-old child, the fifth case reported in Michigan this year.

The announcement didn't say how the child was exposed. The child's family is following isolation protocols, and no related cases have been reported, so far. The health department warned of potential exposure at three locations where the child was taken for medical care. 

Health officials identified the suspected infection on April 3, and tests confirmed the case on April 9.

Elsewhere, the Chicago Department of Public Health reported 3 more cases this week, raising the city's total to 61, most of them linked to an ongoing outbreak at a migrant shelter.

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