A study published in The Lancet Infectious Diseases ranked the top 50 US counties at greatest risk of measles outbreaks based on four factors: population, international air travel volume, nonmedical vaccine exemptions and measles incidence in countries people visit. The top five counties are Cook County, Ill.; Los Angeles County; Miami-Dade County, Fla.; Queens County, N.Y.; and King County, Wash.

CNN Health has an interesting synopsis of the article along with some medical opinions. THose interested in reading the same can click on the attached link.