There's a striking aspect of the recent E. coli outbreak tied to romaine lettuce: 66 percent of those affected are female.

Similarly, when romaine was the culprit of an E. coli outbreak earlier this year, 67 percent of the 210 people infected were women or girls, the same ratio as an outbreak tied to leafy greens in late 2017.

Medical experts have wondered why women and girls seem to be the victims of E. coli more often than men and boys. Dr. Bruce Lee, an associate professor of international health at Johns Hopkins University, explains three potential reasons for the trend.

The most likely contributing factor involves women's diets, which tend to include more vegetables. A 2012 study of nearly 15,000 men and women published in the medical journal Clinical Infectious Diseases found a higher rate of men ate meat and some poultry than women, who ate fruits and vegetables in higher proportions.

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That might explain why an E. coli outbreak stemming from Cargill ground beef this summer affected men in 67 percent of the cases, while a 2016 outbreak in alfalfa sprouts affected women 73 percent of the time, CDC statistics show. Yet, women made up the majority of those affected by a 2015 outbreak tied to Costco rotisserie chicken salad. All of these outbreaks affected fewer people compared to this year's E. coli outbreaks.

British officials also suggested women's diets could be the reason behind the slanted number of E. coli infections. More women than men fell ill during a 2011 E. coli outbreak involving cucumbers, lettuce and tomatoes, The Guardian reported.

"We can't say with complete certainty why women have been disproportionately affected," Bob Adak, chief of the U.K. Health Protection Agency, told the newspaper in 2011, "but in previous outbreaks around the world associated with salad vegetables we have seen women and adults more severely affected than men and children, so it's possible that this could be an indicator of food preference."

Another factor, Lee said, could be the difference between how men and women report their symptoms to their doctors. The high numbers for women could be a result of more of them relaying information to medical professionals. Lee said studies show men are less likely to report symptoms of any type of disease.

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Finally, it's been proposed women react more to E. coli because of differences in their gastrointestinal tracts. Although, Lee said there is no strong evidence to support this. Different outcomes between sexes and races, he added, often are driven by social and behavioral differences, not biological characteristics.

Lee, also executive director of Johns Hopkins' Global Obesity Prevention Center, stresses that's not an excuse to not eat vegetables.

This story is an updated version of an article published on April 21, 2018.

Follow Sean Rossman on Twitter: @SeanRossman