Current Listeria Outbreak – 19 Sick with 2 Deaths: Since September 2015, CDC has been collaborating with public health officials in several states and the FDA to investigate a multistate outbreak of Listeria monocytogenes infections. Twelve people infected with the outbreak strain of Listeria have been reported from six states since July 5, 2015. Twelve people were hospitalized, and one person from Michigan died as a result of listeriosis. One illness was reported in a pregnant woman. Laboratory tests performed on clinical isolates from all 12 ill people showed that the isolates are highly related genetically. Indiana, Massachusetts, Michigan, New Jersey, New York and Pennsylvania states impacted.
The Public Health Agency of Canada is collaborating with federal and provincial public health partners to investigate an outbreak of Listeria monocytogenes infections in five provinces. To date, the source of this outbreak has not been confirmed. However prepackaged leafy greens, salad blends, and salad kits are food items being investigated. Currently, there are seven (7) cases of Listeria monocytogenes in five provinces related to this outbreak: Ontario (3), Quebec (1), New Brunswick (1), Prince Edward Island (1), and Newfoundland and Labrador (1). Individuals became sick between September 2015 and early January 2016. The majority of cases (71%) are female, with an average age of 81 years. All cases have been hospitalized, and one person has died, however it has not been determined if Listeria contributed to the cause of death.
Epidemiologic and laboratory evidence available to date indicate that packaged salads produced at the Dole processing facility in Springfield, Ohio and sold under various brand names are the likely source of this outbreak. The Ohio Department of Agriculture collected a Dole brand Field Greens packaged salad from a retail location and isolated Listeria. Laboratory tests showed that the Listeria isolate from the packaged salad was highly related genetically to isolates from ill people. This packaged salad was produced at the Springfield, Ohio Dole processing facility.
2006 Spinach E. coli Outbreak – 205 Sick with 5 Death: Official word of the spinach outbreak broke with the FDA’s announcement, on September 14, 2006, that a number of E. coli O157:H7 illnesses across the country “may be associated with the consumption of produce.” “Preliminary epidemiological evidence suggests,” the statement continued, “that bagged fresh spinach may be a possible cause of this outbreak.” By the date of the announcement, fifty cases had been reported to the CDC, including eight cases of hemolytic uremic syndrome (HUS) and one death. States reporting illness included Connecticut, Idaho, Indiana, Michigan, New Mexico, Oregon, Utah, and Wisconsin.
The much-publicized outbreak grew substantially over the next several days. By September 15, the FDA had confirmed 94 cases of illness, including fourteen cases of HUS and, sadly, one death. Recognizing the lethality of the developing outbreak, the FDA’s September 15 release warned people should “not eat fresh spinach or fresh spinach containing products.”
Press Releases over the ensuing days announced steady growth in the number of people sickened, hospitalized, and with HUS as a result of the outbreak—109 cases from nineteen states by September 17, and 131 cases from twenty-one states just two days later. The latter statistic included 66 hospitalizations and twenty cases of HUS.
Meanwhile, the FDA and CDC, in conjunction with local and state health agencies from across the country, worked feverishly to figure out the brand names associated with illness. Early statistical analysis suggested that many brands were implicated, but the spinach sold under the several brand names had all come from the Natural Selection Foods processing center in San Juan Batista, California. Accordingly, Natural Selection recalled all of its spinach products with “use by” dates from August 17 to October 1, 2006. The recall, of course, included Dole brand spinach. But further data and study ultimately narrowed the possible sources of the outbreak down to one brand of packaged greens: Dole.
Though epidemiological evidence had already strongly linked Dole to the outbreak, the FDA found the proverbial “smoking gun” on September 20. The bag of Dole baby spinach had been purchased and consumed by an Albuquerque, New Mexico woman, and testing by the New Mexico State Health Department had confirmed that the product was contaminated with E. coli O157:H7 bearing the same genetic marker as the outbreak strain. The FDA announced the critical finding on September 21, 2006—also disclosing the “best by” date on the positive Dole bag of August 30—thereby giving a worried public a bit more information on what spinach products to eat, if any, and what to avoid.
By the date of the FDA’s September 21 announcement, the number of confirmed cases had swelled to 157 people from twenty-three states. Ultimately, the FDA confirmed 204 outbreak-related cases, with 102 hospitalizations, thirty-one cases of HUS, and three deaths, though the actual number of people affected by the outbreak was certainly much larger. In addition to the elderly Wisconsin resident, the FDA stated that the outbreak had claimed the lives of two-year-old Kyle Algood, from Chubbuck, Idaho, and also 81-year-old Ruby Trautz, from Bellevue, Nebraska. The tragedy of this outbreak can hardly be overstated.
Epidemiological and laboratory evidence, which had already proved the link to Natural Selection and Dole, soon revealed that the contaminated spinach had been grown at Paicines Ranch in San Benito County, California. More specifically, investigators had traced the source of the contaminated spinach to one field on the ranch that had been leased by Mission Organics.
Once identified as the likely source for the outbreak, Mission Organics became host to health officials looking for the outbreak strain of E. coli O157:H7. State and federal investigators took hundreds of environmental samples and swabs from the vicinity of the implicated spinach field, which was fifty acres in size, including from a nearby cattle pasture and water source. Investigators also sampled the intestinal lining of feral pigs that had been killed as part of the investigation. Samples from a variety of sources, including the pigs, the water, and cattle feces, tested positive for the same strain of E. coli O157:H7 that had now been isolated in over 205 people nationally. Finally, the outbreak strain of E. coli O157:H7 has been isolated in at least thirteen separate bags of Dole baby spinach. There were five deaths.
Once the investigation was completed, a final report on the outbreak was prepared by the California Food Emergency Response Team (CalFERT), a team comprised of members from the FDA and the California Department of Health Services. The Final Report is replete with facts damning of all those involved in the growing, harvesting, processing, distribution, and sale of the implicated spinach products. For example, speaking of the NSF processing facility, it states:
During the production week from August 14-19, 2006, the NSF South facility had the highest weekly production volume of the month. Between August 13-20, 2006 production email exchanges revealed a string of personnel shortages, including nine absent employees on Sunday, August 13, the date of the weekly extended sanitation shift. Personnel records reveal that a number of absences were due to illness or illness in the family…NSF did not conduct ATP testing on a daily basis as required by the firm’s SOP. No ATP testing was conducted from August 15-25, 2006. One ATP test collected from a scale vibrator failed on August 10, 2006, and no retest was documented.
The Final Report also faulted with NSF’s procedures for monitoring the quality of processing-water, its record-keeping, and its inability to demonstrate that harvesting bins were being washed to prevent cross-contamination.
As for the Mission Organics growing operation, the findings were even more disturbing. The Final Report found that the land on the ranch where the spinach was grown “was primarily utilized for cattle grazing.” Moreover:
Investigators observed evidence of wild pigs in and around the cattle pastures as well as in the row crop growing regions of the ranch….Potential environmental risk factors for E. coli O157:H7 contamination identified during this investigation included the presence of the wild pigs in and around spinach fields and the proximity of irrigation wells used for ready-to-eat produce to surface waterways exposed to feces from cattle and wildlife.
2005 Lettuce E. coli Outbreak – 32 Sick: On September 22, 2005 the Minnesota Department of Health (MDH) Public Health Laboratory (PHL) received an E. coli O157:H7 isolate for confirmatory testing and Pulse Field Gel Electrophoresis (PFGE) subtyping. PFGE results were reported on September 26 and uploaded to PulseNet, a national database of PFGE patterns or “fingerprints” maintained at the federal Centers for Disease Control and Prevention (CDC). The pattern derived from digestion with the restriction endonuclease Xba I was assigned Pattern number EXHX01.0238. The isolate was soon tested with a second enzyme, Bln I, and the resulting pattern was assigned pattern number EXHA26.1040. Prior to September 19, the Bln I pattern had not been posted on PulseNet.
Isolates obtained from culture of stool submitted by two new ill patients were received at the MDH PHL on September 23, 2005 and subtyped. PFGE results showed that the two new isolates and the isolate received on September 22 were indistinguishable by two enzymes. By September 29, 2005 isolates obtained from seven more patients arrived at the MDH PHL for further analysis. Public health investigators recognized that an E. coli O157:H7 outbreak was underway in Minnesota.
While laboratory testing was performed, MDH epidemiologists conducted preliminary interviews with patients who were laboratory confirmed with E. coli O157:H7. On the morning of September 28 investigators had identified pre-packaged lettuce produced by Dole Food Company, Inc. as the likely vehicle of transmission for infection with E. coli O157:H7. A supplemental questionnaire focusing on the type and brand of lettuce consumed and where it was purchased, was developed and administered to case-patients previously interviewed and newly identified cases. On September 29 Minnesota Department of Agriculture (MDA) staff collected a bag of Dole lettuce at the home of a case patient and began microbiologic testing for the presence of E. coli O157:H7.
On September 30 the MDH issued a press release advising the public that 11 cases of E. coli O157:H7 had been identified in Minnesota residents who had eaten Dole lettuce purchased from at least four different stores in the Twin Cities area. Persons with symptoms of E. coli were told to contact the MDH and their physician. Dr. Chris Braden at the Foodborne and Diarrheal Disease Branch at the CDC announced that no other states were reporting outbreak associated cases.
Meanwhile MDA microbiologists continued to process lettuce specimens obtained from households with cases of confirmed E. coli O157:H7. On Monday, October 3 the agency reported that sample number M-05-2310, Lot Number B250215B received on September 30 had tested positive for E. coli O157:H7. The isolate obtained from the sample was sent to the MDH for PFGE analysis. The resulting pattern was indistinguishable to the pattern identified in case-patients. A second specimen, M-05-2318, lot number unavailable, would also yield positive results.
News of the positive lettuce specimen prompted the Food and Drug Administration (FDA) to issue a nationwide health alert regarding Dole pre-packaged salads on October 2. The FDA announcement reiterated warnings expressed in the MDH press release and further described the Dole products associated with illness, Classic Romaine, American Blend, and Greener Selection. Although cases had only been identified in Minnesota, the product was noted to have been distributed nationwide.
It would not be long before cases of E. coli O157:H7 in Wisconsin and Oregon would be recognized. The Wisconsin case was a 12 year old female with E. coli O157:H7 who had a history of eating Dole pre-packaged lettuce. PFGE subtyping showed that her isolate was indistinguishable to the EXHX01.0238 pattern and one band different on the second enzyme pattern. Despite the one band difference, MDH molecular epidemiologists considered the girl to be part of the outbreak concluding that the difference was not enough to preclude the case from being considered outbreak related.
The Oregon case was indisputably associated with consumption of Dole pre-packaged salad mix. A 60 year old Portland resident was hospitalized and laboratory confirmed with E. coli O157:H7 on September 21, 2005. The patient had experienced onset of symptoms on September 18, four days after purchasing and consuming Dole brand “Classic Romaine” salad mix. Michael Roberson, representative for Albertsons’, the grocery store of purchase, confirmed that the chain’s Portland area distributing center had received Dole Greener Selection and Dole Classic Romaine. A portion of the salad mix was still in the patient’s refrigerator. A photograph taken of the packaging documents that Ms. Scheetz purchased Dole salad mix with a “Best if Used By” date of 9/23/05, lot number was B250215B. PFGE subtyping showed that the Oregon isolate was indistinguishable by two enzymes to other ill Dole lettuce consumers in Minnesota.
Aware of the potential severity of an E. coli O157:H7 outbreak, the FDA and the Food and Drug Branch at the California Department of Health Services initiated an investigation at the Dole processing plant. Preliminary information indicated that 22,321 cases of Dole pre-packaged lettuce with a “Best If Used By” date of 9/23/05 and a production code starting with “B250” were shipped from a single Dole processing facility in central California to 34 states in early September. Investigators estimated that since each case contained between 6 and 12 bags, approximately 244,866 bags of lettuce had made it to market.
On October 11, 2005 the MDH counted 23 laboratory confirmed cases of E. coli O157:H7 and seven epidemiologically linked cases. Illness onset dates ranged from September 16 to September 30. Two cases had developed Hemolytic Uremic Syndrome (HUS). Oregon and Wisconsin reported one case each. Case control study data show a statistically significant association between illness and consuming Dole pre-packaged lettuce with a matched odds ratio of 6.8, 95% confidence interval, 1.4-31.9, and a p-value of 0.01. The California Department of Health Services continues to conduct a trace back investigation to farms implicated in earlier lettuce outbreaks. A final outbreak report and traceback summary has not been provided. Eventually, a total of 32 persons from three states would be linked to the E. coli O157:H7 outbreak.