Kelly Aherns has always topped her meals at Chipotle with fresh tomato salsa.

But last August, not long after ordering her usual chicken bowl, the 31-year-old Minneapolis resident came down with a fever and cramps. It was the beginning of months of ill health.

Aherns was among 973 people in Minnesota with state-confirmed cases of salmonella, the most since health officials started tracking in the early 1990s. Cases were up 35 percent over 2014, according to the Minnesota Department of Health, with 115 people affected by the outbreak linked to Chipotle.

“It was a huge outbreak, the biggest salmonella outbreak [in this state] since 1994,” said Kirk Smith, the health department’s head of foodborne disease investigations.

The Chipotle case, along with a huge national outbreak last year involving cucumbers, highlights a growing problem: the spread of foodborne disease through produce.

Tomatoes connected to the Chipotle outbreak were traced back to a farm in Virginia, a big tomato-growing area linked to several salmonella outbreaks in the past 15 years.

Salmonella and the even more virulent E. coli 0157 bacteria originate in the guts of animals, making their way into nature through excrement. The waste can then contaminate water or soil, ultimately transmitting bad bacteria to tomatoes, lettuce and other produce, said Ian Williams, head of outbreak control and prevention for the U.S. Centers for Disease Control and Prevention (CDC).



“One of the problems with produce is there is no kill step,” he said, noting that salmonella and other pathogens in meat are usually zapped by cooking. “What is contaminated in the field is what you will be eating in your kitchen.”

Salmonella is the most common cause of bacteria-related foodborne illness. While only a small number of cases get reported, the CDC estimates that 1 million people a year are sickened by the bug, with 19,000 hospitalized.

It’s not often fatal — salmonella is estimated to kill almost 400 Americans annually — but it can be a health nightmare.

“It was definitely the illness of a lifetime,” said Susan Wikstrom, 44, who got severe intestinal symptoms in August after eating chicken tacos with the tomato salsa at Chipotle.

“It was probably a good full week of not eating, severe dehydration, high fevers and a couple of trips to the hospital,” said the White Bear Lake resident. “I felt crappy for two or three months.”

Aherns’ health woes went on for even longer.

After she was waylaid by salmonella’s typical digestive maladies, she continued to feel fatigued and lightheaded, and then developed tendinitis in her Achilles’ tendon — a possible result of salmonella infection. Then, she was diagnosed with C. difficile, another intestinal bacterium, which could have been caused by an antibiotic she had taken to fight her salmonella infection.

Aherns had contracted a strain of Salmonella Newport that matched a strain traced to the Chipotle outbreak in Minnesota, according to a lawsuit she filed in federal court against Chipotle. Wikstrom said the same in a similar suit.

Chipotle, hit by a series of foodborne illness outbreaks last year, did not return calls for comment.

Another outbreak

The largest U.S. foodborne incident in 2015 was a Salmonella Poona outbreak that sickened 888 people nationwide, killing six. That outbreak included 43 illnesses in Minnesota, though no deaths.

The culprit: cucumbers imported from Mexico. It was the third significant U.S. outbreak of salmonella linked to cucumbers in three years.

As demand has grown for fruits and vegetables, produce has become a national and even international business, said Smith of Minnesota’s health department. “There is more mass production. So, when something goes wrong, it’s usually big enough for us to detect,” he said.

Chipotle was cooperative in Minnesota’s investigation, Smith said, and analyzed its own supply chain data to determine that tomatoes linked to the outbreak likely came from a farm in Virginia.

According to the health department, the tomatoes were sold by Lipman Produce, an Immokalee, Fla.-based company that on its website bills itself as North America’s largest open field tomato grower.

Lipman’s CEO didn’t respond to requests for comment, but in a response to a lawsuit, the company denied that it was the source of the outbreak in Minnesota.

The Virginia tomatoes were sold to a produce wholesaler that packed or repacked them, and then moved on to a distributor that delivered them to Chipotle. Where exactly the tomatoes were tainted has not been identified, and the U.S. Food and Drug Administration (FDA) says it’s investigating.

Seeking the source

Smith and other foodborne illness experts say contamination of produce usually occurs in unsanitary packing houses or in the fields, particularly through contaminated water.

From 1990 to 2010, there were 15 multistate salmonella outbreaks linked to raw tomatoes; four were traced to farms or packing houses in Virginia.

Virginia’s tomato industry is centered on its eastern shore, a peninsula framed by Chesapeake Bay and the Atlantic Ocean. Its gull and geese populations have been fingered as possible carriers of salmonella, as have chicken farms and processors to the north.

Whatever the reason, surface water and sediment in the area appear to be “long-term reservoirs of persistent and endemic contamination of this environment,” according to a study published last year in Frontiers in Microbiology.

“We feel the [salmonella] population is quite established in these waters,” said Rebecca Bell, an FDA microbiologist who led the study. “It’s a very hardy organism.”

Virginia agricultural officials say farmers are well aware of the issue and have improved their practices over the past six years, routinely testing water for pathogens and using underground irrigation systems that minimize contact with plant foliage and fruit, said Steven Rideout, director of Virginia Tech’s Eastern Shore Agricultural Research and Extension Center. Plus, growers chlorinate irrigation water to kill bacteria.

“Our growers view food safety as their number one priority,” Rideout said.