CHICAGO (CBS) — Warmer temperatures are impacting the food supply and its safety, experts warned amid an outbreak of E. coli that has struck McDonald’s Quarter Pounders.

Experts said pathogens—the bacteria that can make us sick—are changing with the weather.

“It’s an adjustment due to climate change,” said Pratik Banerjee, who teaches food safety at the University of Illinois at Urbana-Champaign, “and some of these adjustments are not good.”

Banerjee is currently studying the impact of climate on the food supply.

“There is not a magic wand that can be there and the food would be absolutely safe, right?” he said. “So the goal is to reduce the risk.”

Similar research is happening at the Institute for Food Safety at the Illinois Institute of Technology.

“This is disrupting a lot of the larger ecosystem in terms of how microorganisms behave,” said Dr. Alvin Lee, who leads IFSH

Slivered onions placed on Quarter Pounders are the likely source of the E. coli contamination leading to the McDonald’s outbreak, according to the U.S. Food and Drug Administration. According to those with whom CBS News Chicago connected for this story, the McDonald’s outbreak is a reminder that climate change is real.

“People who don’t believe in global warming are going to believe in global warming eventually,” said attorney Bill Marler of Marler Clark, The Food Safety Law Firm, “because there’s a lot of studies that are coming out now that are showing that certain pathogens like E. coli, salmonella, campylobacter are adapting better to a heated environment than we are.”

Marler has represented victims of outbreaks across the country for decades as a foodborne illness lawyer. He said some pathogens that contaminate food are even showing up in the U.S. for the first time thanks to climate change.

“There are bugs in the United States we never saw before. We used to never see Cyclospora as a bacterial or viral problem. Now, we are seeing it all the time in the United States, and that’s because temperatures are warming,” he said. “It used to be a South American problem. Now, it’s a U.S. problem.”

Marler said with changing temperatures impacting pathogens in the food supply, the industry needs to make changes to keep up.

“We’ve got to adapt and right now,” he said. “The FDA and the industry is being caught flat footed.”

But Banerjee said while scientists don’t have all the answers yet, the work happening right now at UIUC should be making a difference soon.

“The focus of my own research is to understand how the pathogens adapt to these situations, and what is the outcome of that adaptation,” he said.

Among Banerjee’s studies is one in which E. coli bacterial cells were exposed to lettuce leaf cells in refrigerated conditions—then observed to find out what the refrigeration meant for infecting mammalian cells.

Tara Molina

Tara Molina is a general assignment reporter for CBS2 Chicago.