Federal officials this week released the first reports on a Salmonella outbreak in 2016 that sickened more than 30 people across nine states and was traced to fresh hot peppers.

The outbreak hit people from Texas to Minnesota, causing the hospitalization of at least eight out of 32 confirmed victims, according to a report in the “Morbidity and Mortality Weekly Report” from the Centers for Disease Control and Prevention.

“This is the first report of this outbreak,” a CDC spokeswoman told Food Safety News on Thursday.

“Investigators could not determine what specific type of hot pepper was causing illness, or which farm was producing the peppers. Due to the short shelf-life of fresh peppers, the contaminated peppers were most likely no longer being sold or served when investigators suspected peppers as the outbreak source.”

The Food and Drug Administration had similar reasons for not alerting the public during the 2016 outbreak, which stretched from May 6 through July 9.

“The FDA worked with CDC on this outbreak, however the traceback investigation was unable to uncover a common source for the peppers at the time and therefore we did not have any actionable information to share with consumers,” a spokesman from the Food and Drug Administration told Food Safety News Thursday afternoon.

Coincidentally, the FDA issued an Import Alert on June 21, 2016, for fresh Anaheim peppers from produce consolidator Elias Gerardo Gonzalez Valdez in Nuevo León, Mexico. The alert allowed for Anaheim peppers from Valdez to be held at the U.S. border without inspection. But the alert was not related to the outbreak.

“The import alert was issued because of a positive sample collected during our micro-surveillance sampling of hot peppers,” the FDA spokesman said Thursday.

“We had begun this sampling assignment to fill some data gaps in our knowledge about hot peppers and to learn more about potential rates of contamination in these products. We received the results for this pepper right about the same time that we were becoming aware of the outbreak.”

Peppers among the usual suspects

Potential pathogen problems associated with fresh peppers spurred the FDA to initiate a special 18-month testing assignment program for the commodity in late 2015. The agency cited outbreaks, deaths and recalls related to fresh hot peppers when it announced it would be conducting the “micro-surveillance.”

Another contributing factor to the FDA decision to conduct the special testing of hot peppers is the fact that there are numerous opportunities for the commodity to be contaminated because peppers frequently come into contact with contaminated water, soil or equipment during growing, harvesting, and/or post-harvest activities.

“In 2008, fresh hot peppers were associated with an outbreak that caused 1,500 illnesses, 308 hospitalizations and two deaths. Additionally, since 2010, Salmonella spp. has been responsible for eight product recalls involving fresh hot peppers, which can be a ‘stealth component’ in multi-ingredient dishes,” according to FDA’s information page on the pepper testing program.

“As a result of these incidents, the FDA is seeking information on the prevalence of Salmonella spp., E. coli, and Shiga toxin–producing E. coli in fresh hot peppers.”

FDA’s plans called for the collection and testing of 1,600 hot pepper samples — 320 domestic, and 1,280 of international origin. As of April 1, the agency had collected 310 domestic samples and 1,255 import samples. Of those, FDA tested 309 of the domestic samples for Salmonella, with only one returning positive results. That’s about 0.3 percent with positive results.

Of the import samples collected, FDA tested 1,211 for Salmonella and found 44 of them — 3.6 percent — positive for the pathogen.

“As the testing is still underway, no conclusions can be drawn at this time,” according to the most recent update, which FDA posted on April 1.

Connecting the dots

Neither the FDA nor CDC could definitively connect the 2016 outbreak victims to a specific type of hot pepper or a specific grower or packer. However, a sample of Anaheim pepper from the Nuevo León produce consolidator that FDA tested in April 2016 turned out to be a genetic match for Salmonella Anatum isolated from victims.

The big picture didn’t come into focus, though, until months later.

In June 2016, the CDC’s PulseNet database identified a cluster of 16 people from four states who had Salmonella Anatum infections with an indistinguishable pulsed-field gel electrophoresis (PFGE) pattern, indicating a common source.

“This rare PFGE pattern had been seen only 24 times previously in the PulseNet database, compared with common PFGE patterns for this serotype which have been seen in the database hundreds of times,” according to the CDC report published this week.

Standard outbreak interview and investigation techniques did not yield many clues, so the CDC and state investigators in Minnesota started having open-ended interviews with outbreak victims. Among 18 patients interviewed, 14 reported eating or possibly eating fresh hot peppers, or reported eating an item containing fresh hot peppers before becoming sick.

“Nine patients reported eating peppers at restaurants, two reported eating peppers both at restaurants and at home, and three did not specify a location,” the CDC reported.

Investigators started looking at restaurants where victims reported consuming peppers. They collected recipes for reported menu items, including salsa, and reviewed invoices to identify common ingredients.

The FDA conducted traceback on peppers served at three restaurants in Minnesota and Texas. Two of those restaurants received peppers from the Nuevo León produce consolidator named in the FDA import alert. The third restaurant received peppers from multiple firms in Mexico, including Valdez in Nuevo León.

“FDA collected seven additional samples of hot peppers, including serrano, habanero, jalapeño, and bell peppers, from (the consolidator) as part of the outbreak investigation; none yielded Salmonella,” according to the CDC report.

“On June 21, 2016, before the epidemiologic investigation began, FDA placed (the consolidator) on import alert for Anaheim peppers because they could be contaminated with Salmonella. …There were only two outbreak-associated illnesses reported after the import alert was issued.”

An estimated 1 million people in the U.S. are sickened with Salmonella infections every year, according to the CDC. Of those, about 400 people die.

There were four fresh pepper recalls because of Salmonella during the outbreak period in the U.S. and Canada:

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