By April 26, just four months into 2019, the United States had already reported more measles cases than any year on record since the disease was officially declared eliminated from the country in 2000, according to data from the CDC.
Between Jan. 1, 2019 and April 26, 2019, there were 704 confirmed measles cases in the U.S. across 22 states. Just a quarter of the way into 2019, that's already nearly double the total of 372 reported cases in 2018, and nearly six times the total of 120 reported cases in 2017.
In response to this surge of outbreaks, a team of researchers has come up with a list of the 25 U.S. counties that have the highest risk of experiencing a measles outbreak in 2019.
The analysis, published in The Lancet Infectious Diseases, found that there are two main contributing factors fueling outbreaks of measles in the United States: reintroduction of the virus to specific locations through international travel, and low vaccination rates that are a result of non-medical exemptions.
To determine the individual risk of each U.S. county, the researchers used a quantitative model that analyzed the amount of international travel to each area, non-medical exemption rates in the county, county population and the incidence rate of measles cases in the foreign country where travel originated. This analysis was performed for each year between 2011 and 2018.
The analysis showed that Cook County, Illinois is most at risk, followed closely by Los Angeles County, California. Miami-Dade County, Florida and Queens County, New York rank third and fourth, respectively.
The research team also conducted a predictive analysis to see how their findings stacked up to data collected from the beginning of 2019 until April 15. They found that their results are consistent with reports of measles cases in the U.S. thus far this year.
Some of the counties on the predictive list of 25 most at risk have not yet had a measles outbreak in 2019, but each such county is either served by an international airport or lies adjacent to a county where there has already been an outbreak. The analysis suggests that these counties should be targeted for enhanced vaccination efforts.
Top 25 U.S. counties predicted to be at highest risk for measles outbreaks in 2019:
1. Cook County, Illinois
2. Los Angeles County, California
3. Miami-Dade County, Florida
4. Queens County, New York
5. King County, Washington
6. Maricopa County, Arizona
7. Broward County, Florida
8. Clark County, Nevada
9. Harris County, Texas
10. Honolulu County, Hawaii
11. Wayne County, Michigan
12. Tarrant County, Texas
13. Multnomah County, Oregon
14. Orange County, Florida
15. Essex County, New Jersey
16. Denver County, Colorado
17. Hillsborough County, Florida
18. San Mateo, California
19. Salt Lake County, Utah
20. Suffolk County, Massachusetts
21. Clayton County, Georgia
22. Travis County, Texas
23. Hennepin County, Minnesota
24. Loudoun County, Virginia
25. San Diego County, California