an unusual new study.

Researchers at the University of Texas at Austin and Johns Hopkins University mapped the 25 American counties most at risk of measles because of their vaccine-exemption rates and proximity to airports.

A similar map published last year proved surprisingly accurate at forecasting many of this year’s cases. But both groups of scientists failed to predict the measles outbreak that began in Brooklyn, currently the nation’s largest.

These prediction models need refining, one expert noted, and the Centers for Disease Control and Prevention should make it a priority in order to get ahead of measles cases.

counties across the country had nonmedical vaccination exemptions — which include “religious,” “philosophical” or “personal belief” exemptions, depending on state law.

The team then focused on counties with international airports, because every American outbreak since 2000 has begun with a case imported from overseas.

They gave greater weight to airports with many passengers arriving from countries with thousands of measles cases, including India, China, Mexico, Japan, Ukraine, the Philippines and Thailand.

However, both studies failed to foresee what is now the country’s largest outbreak — the one among Orthodox Jews in the Williamsburg neighborhood of New York — which is in Brooklyn, not Queens.

virus spread from Ukraine to Orthodox Jewish communities in Israel. One month later, Orthodox Jews from New York carried measles almost simultaneously to Brooklyn and to suburban Rockland County, N.Y. The outbreak spread from New York to Orthodox communities in Michigan.

“What we did not calculate at all was that it would come from Israel,” said Sahotra Sarkar, a professor of philosophy and integrative biology at the University of Texas at Austin and a co-author of the new study.

A similar study published last June in PLOS Medicine ranked the risk of measles outbreaks in 18 states with philosophical or personal belief exemptions to vaccination. The research was prescient: almost half the “hotspot” metropolitan areas the scientists noted — particularly Washington State, Texas and Michigan — saw outbreaks this year.

“In the major leagues, that’s an all-star batting average,” said Dr. Peter J. Hotez, a director of the Texas Children’s Hospital Center for Vaccine Development and a co-author of the PLOS Medicine study.

Dr. Hotez and his colleagues did not look at New York State because it does not have “philosophical” exemptions to vaccination, although the state permits religious ones — a loophole that the legislature is considering eliminating.

“What I never expected was an outbreak in Jewish communities,” Dr. Hotez joked. “In my book, Jews make the vaccines.” (Dr. Hotez, who is Jewish and researches vaccines against tropical diseases, cited such pioneers as Albert Sabin, Jonas Salk, Stanley Plotkin and Rachel Schneerson.)