Mike Hornick of The Packer writes that health officials will begin routinely asking listeria outbreak victims if they consumed leafy greens, according to the Centers for Disease Control and Prevention.

The addition of leafy greens to the standard federal questionnaire on listeria comes in response to last winter’s outbreak linked to a Dole Fresh Vegetables salad plant in Springfield, Ohio. That outbreak sickened 33 in the U.S. and Canada and was tied to at least one death. Dole stopped production in January and reopened the plant in April.

It was the first reported listeria outbreak in the U.S. associated with leafy greens, and the eighth with fresh produce. All occurred since 2008, according to an Aug. 26 report by the CDC.

“It is unclear whether the appearance of these outbreaks might be attributed to improved outbreak detection, changes in consumer behavior, or changes in production and distribution,” the report says. “Fresh produce processors are advised to review food safety plans and consider incorporating measures to avoid the growth and persistence of listeria.”

In the Ohio centered outbreak, the older questionnaire failed to identify a common source for seven infections reported by Nov. 30.

Then in December and January, eight new or previously interviewed patients or their representatives took part in open-ended interviews or provided shopper card records.

That revealed the connection. All reported consuming leafy greens in the month before the onset of illness.

Among these, seven reported romaine and six reported spinach, higher than national food consumption estimates of 47% and 24%, respectively. Six patients recalled consuming packaged salad, according to the report.

Dole Fresh Vegetables denied responsibility in two foodborne illness lawsuits that followed the outbreak.