An E. coli outbreak that has sickened at least 75 people and killed one person is a reminder of the contamination risk that can plague certain types of fresh produce, food safety experts say.

The four professors said they themselves routinely avoid certain raw fruits and vegetables, such as Brussels sprouts, bagged green salads and cantaloupe.

Although the investigation is ongoing, federal officials suspect that pre-washed, sliced ​​onions served raw on McDonald’s Quarter Pounders are the likely source of the E. coli outbreak. For those who specialize in foodborne illness prevention, the news came as no surprise.

Don Schaffner, a professor of food sciences at Rutgers University, said the more food is handled and processed during its journey from the farm to a restaurant or supermarket, the more opportunities there are for bacteria to be introduced or spread. This includes cutting, pre-washing or adding ingredients.

“The more manipulation you do, the more places there are for things to go wrong,” Schaffner said.

When fruits and vegetables are served uncooked, there is no natural opportunity to heat bacteria. This has contributed to previous E. coli outbreaks linked to agricultural products, including an outbreak in pre-packaged baby spinach in 2006 that sickened more than 200 people, and dozens of cases of E. coli and other foodborne illnesses linked brought with contaminated sprouts. Melon is also contaminated with pathogens, including salmonella and listeria.

“If you just look at the number of outbreaks and recalls over the last 15 years, we tend to see more cases of E. coli associated with its production,” said Darin Detwiler, a professor of food regulatory policy at Northeastern University.

Although serious E. coli incidents in meat occurred decades ago — including an outbreak linked to Jack in the Box hamburgers that sickened hundreds of people and killed four in the early 1990s — there were changes in federal regulations and better understanding of the proper cooking temperatures needed to kill the bacteria have reduced these cases.

Barbara Kowalcyk, director of the Institute for Food Safety and Nutrition Security at the George Washington University Milken Institute School of Public Health, said she makes an effort to avoid eating bagged vegetables, Brussels sprouts and cantaloupe. Bags or containers of lettuce or other leafy greens can trap bacteria and create an environment in which they can multiply, she said, so for salads she opts for grocery store lettuce heads instead.

“I just throw away any leaves that are torn or damaged because that’s where the bacteria can get in,” she said. “And I usually take off the outer leaves and throw them away.”

She then washes and dries the lettuce thoroughly.

“The key is running water and using a clean paper towel to dry it,” she said. “The bacteria are quite sticky and friction causes them to loosen.”

Schaffner said previous E. coli outbreaks involving pre-washed leafy greens resulted from insufficient chlorine in the water during rinsing. With sprouts, it’s a different concern, he said: The seeds are exposed to warm temperatures and as they germinate, nutrients are released into the water that allows bacteria to grow.

Sliced ​​melons, on the other hand, can be a common breeding ground for pathogens, especially if left outside.

“I do a lot of workshops, and they often have cut fruit on the breakfast buffet, and that fruit stays there all day,” Schaffner says. “We did research to show that its physical appearance doesn’t change, but bacteria can grow like no one’s business.”

Detwiler is particularly careful to avoid cantaloupe because of its webbed rind, where bacteria can easily hide.

“It’s one of the deadliest products out there,” he said. “Cantaloupe has a perfect pH level and you can’t clean the outside enough.”

E. coli spreads in the environment through animal or human feces and from there can contaminate food and water. Although significant improvements in agriculture have minimized the spread of pathogens in fields where produce is grown, experts say it is still important for consumers to consider the risk of E. coli – especially for young children, those over 65 years and anyone with a compromised immune system. including those who are pregnant.

“This is really a unique pathogen because there is a very low infectious dose. So it only takes a few cells to make someone very sick,” says Kali Kniel, professor of microbial food safety at the University of Delaware.

The food safety experts interviewed also said they avoid rare or undercooked meat, poultry, fish and eggs and don’t drink unpasteurized milk.

Some also said they look for signs of cleanliness when dining out.

“When I go to a restaurant that I’m not familiar with, one of the first things I do is go to the restroom, because if the restroom looks terrible — like no one has cleaned it in a long time — then I don’t . I even want to know what the kitchen looks like,” Detwiler said.

That said, fast-food restaurants are generally not hotbeds for foodborne illness, and Detwiler said McDonald’s has a “long history of being a very prominent leader” in food safety.

Kowalcyk agreed, adding that as a large chain, McDonald’s likely has more procedures in place to train employees on how to prevent contamination.

“I don’t really think any particular type of restaurant would be riskier than others, except that large organizations tend to have a lot of resources, and smaller organizations tend to have less resources or expertise,” she said.

According to the Centers for Disease Control and Prevention, raw onions have not previously been known to be linked to an outbreak of this specific strain of E. coli. But onions have become contaminated with pathogens in recent years: outbreaks of salmonella have been linked to them.

Kniel said she expects improvements will be made as a result of the growing number of E. coli cases.

“Every time there is an outbreak, we learn something,” she said.

For consumers concerned about E. coli, Schaffner acknowledged that it is impossible to avoid every item linked to foodborne illness.

“If you stop eating foods if they are linked to outbreaks, you wouldn’t get much of a diet,” he said. “As a good friend of mine joked, the risks of not eating are still greater than the risks of eating.”