Measles Cases Top Last Year’s Numbers

As of Aug. 22, 227 cases of measles have been reported to the U.S. Centers for Disease Control and Prevention (CDC) from 28 states and the District of Columbia.

Measles is an airborne, extremely infectious, and potentially severe rash illness. Before the measles vaccine was introduced, an estimated 48,000 people were hospitalized and 400–500 people died in the United States of measles each year.

More than a dozen measles outbreaks (defined as three or more related cases) have driven case counts this year, and 68% of cases are outbreak-associated. In comparison, four outbreaks were reported in total last year, and 49% of cases were outbreak-associated.

This year, the Illinois Department of Public Health reported the largest measles outbreak to affect the state since 1990 resulted in 67 cases with the vast majority linked to a Chicago shelter. Illinois is the leading state for measles cases this year.

Most (39%) of the infected are under 5 years old, with 30% aged 5 to 19 years old and 31% 20 years old or more. The majority (86%) of cases occurred in unvaccinated humans or those with an unknown vaccination status. Of all the cases this year, 44% resulted in hospitalization for isolation or for management of measles complications. Most of those hospitalized were children under 5 years.

Measles was declared eliminated in the U.S. in 2000 due to a very high percentage of people receiving the measles, mumps, and rubella (MMR) vaccine. In recent years, however:

• U.S. MMR coverage among kindergarteners dropped below the 95% coverage target—much lower in some communities—and is continuing to decrease.
• Global measles activity is increasing, resulting in more chances of an unvaccinated person infected with measles abroad returning to the U.S.

As CMM previously reported, measles cases nearly doubled globally from 2022 to 2023.