Measles Cases Highest Since 1992, Now in 24 States, CDC Says

Troy Brown, RN

May 20, 2019

The number of confirmed measles cases in the United States this year rose by 41 in the past week, to 880 cases from Jan. 1 to May 17. Cases have now been confirmed in 24 states, according to data from the US Centers for Disease Control and Prevention.

This is the highest number of cases in the United States since the entire year of 1992, when there were 963 cases in 39 states. The disease was eliminated here in 2000.


States now reporting confirmed measles cases are Arizona, California, Colorado, Connecticut, Florida, Georgia, Illinois, Indiana, Iowa, Kentucky, Maryland, Massachusetts, Michigan, Missouri, Nevada, New Hampshire, New Jersey, New York, Oklahoma, Oregon, Pennsylvania, Texas, Tennessee, and Washington.

Chicago Case Has Some Worried

On Friday, the Chicago Department of Public Health confirmed a case of measles in an individual who took the blue line elevated train from O'Hare International Airport to the University of Illinois Chicago (UIC) campus the day before and spent time in the Chicago Loop, Millennium Park, and in retail establishments along State Street between Monroe and Randolph Streets, and on South Canal Street. Additional exposures may have occurred at UIC Student Center East Friday morning.

"The University of Illinois at Chicago continues to work closely with the Chicago Department of Public Health (CDPH) to identify and attempt to contact all students, staff and faculty who are known to have come in direct contact with an individual who has a confirmed measles infection and who visited the university on May 16 and 17. We believe there are only a limited number of individuals on the campus that may have been exposed and not immune," according to a UIC news release.

The latest case brings the total to eight confirmed cases of measles in Illinois.

Some US Counties at Higher Risk

Researchers say Cook County, where Chicago is located, is among US counties at particular risk for large measles epidemics such as those that have occurred in Europe recently.

Sahotra Sarkar, PhD, departments of Philosophy and Integrative Biology, University of Texas, Austin, and colleagues published their findings online
May 9 in The Lancet.

They used four factors to develop a quantitative model for identifying the US counties with the highest risk for a measles outbreak in 2019: international air travel volume to the destination county, nonmedical exemption rates in the county, county population, and the incidence rate of the measles outbreak at the origin of travel.

The risk was highest in Cook County, Illinois (relative risk [RR], 1.000); followed by Los Angeles County, California (RR, 0.432); Miami-Dade County, Florida (RR, 0.381); Queens County (the authors refer to the borough of Queens as Queens County in the article since outbreaks in the region are "spatially consistent" with Queens and Brooklyn), New York (RR, 0.293); King County, Washington (RR, 0.140)l Maricopa County, Arizona (RR, 0.123); Broward County, Florida (RR, 0.106); Clark County, Nevada (RR, 0.093); Harris County, Texas (RR, 0.087); and Honolulu County, Hawaii (RR, 0.067).

The investigators say the study confirms their hypothesis that reintroduction of the measles virus at individual localities through travel from countries experiencing outbreaks and low vaccination rates resulting from nonmedical exemptions are the two main drivers of the resurgence of measles in the US.

"Perhaps the most important implication of our results (appendix) is to suggest enhanced surveillance in counties such as Cook, Illinois, and Los Angeles, California, which have each so far only reported one case of measles in 2019 but, because of the presence of major international airports, could serve as the fulcrum of continuous importation of the measles virus into the USA," Sarkar and colleagues explain.

Scattered Outbreaks

Of the confirmed cases in the US so far, 729 were reported in New York State. In Rockland County, New York, there were 231 confirmed cases as of May 17, and in Brooklyn and Queens, New York City, as of today there have been 523 confirmed cases of measles since September. These cases were largely associated with unvaccinated individuals in Orthodox Jewish communities there.

In Michigan as of Friday, there have been 44 cases since March 13. In California, there have been 45 confirmed cases as of May 15.

Georgia has reported six cases as of April 29. Five cases have been reported  in Maryland as of May 9 and five cases have occurred in Pennsylvania as of May 6.

Washington state is currently experiencing an outbreak in three Puget Sound counties — King County (three cases), Pierce County (two cases), and Snohomish County (one case). The outbreak began on May 9. An earlier outbreak infected 72 individuals during February and March and that outbreak has been declared over.

Sarkar and colleagues have disclosed no relevant financial relationships.

The Lancet. Published online May 9, 2019. Full text, Supplementary Appendix

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