I have been thinking today about what growers in Yuma are going to do next season?  With the FDA and CDC fingering the water from an irrigation canal that flowed by a feedlot with some 100,000 cows, you have to wonder what is going to happen next season if nothing changes?  What are grocery stores and restaurants going to do?  What will consumers demand?

This Years Outbreak

In April 2018 local, state and federal public health and agriculture agencies announced an outbreak of E. coli O157:H7 linked to romaine lettuce from the Yuma, Arizona growing area. On June 28, 2018 the Centers for Disease Control and Prevention (CDC) declared the outbreak over.

The outbreak strain was identified as PulseNet strain EXHX01.0047/EXHA26.0626. A total of 210 people in the United States infected with the outbreak strain of E. coli O157:H7 were reported from 36 states.

States reporting outbreak associated case patients

Illnesses started on dates ranging from March 13, 2018 to June 6, 2018. Ill people ranged in age from 1 to 88 years, with a median age of 28 years. Sixty-seven percent of ill people were female. Of 201 people with information available, 96 (48%) were hospitalized, including 27 people who developed hemolytic uremic syndrome (HUS), a type of kidney failure. Five deaths were reported from Arkansas, California, Minnesota (2), and New York.

WGS analysis of isolates from 184 ill people identified antibiotic resistance to chloramphenicol, streptomycin, sulfisoxazole, tetracycline, and trimethoprim-sulfamethoxazole. Standard antibiotic resistance testing of eight clinical isolates by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory confirmed these findings. Isolates from four of those ill people also contained genes for resistance to ampicillin and ceftriaxone.

In Canada there were eight illnesses of E. coli O157:H7 with a similar genetic fingerprint to illnesses reported in the U.S. investigation. The eight Canadian illnesses were reported in five provinces:  British Columbia (1), Alberta (1), Saskatchewan (2), Ontario (3), and Quebec (1). Individuals in Canada became sick between March and April 2018. One patient was hospitalized and no one died. Based on the evidence from the U.S. outbreak investigation and information provided by individuals who became sick, Canadian investigators concluded that the likely source of illness in Canada was contaminated romaine lettuce. All of the individuals reported having eaten romaine lettuce at home or in prepared salads purchased at grocery stores, restaurants and fast food chains before their illnesses occurred. Two Canadians did report traveling to the U.S. before getting sick and eating romaine lettuce while they were there.[1]

The FDA and state and local regulatory officials traced the romaine lettuce to many farms in the Yuma growing region. The FDA, along with CDC and state partners, started an environmental assessment in the Yuma growing region and collected samples of water, soil, and manure. CDC laboratory testing identified the outbreak strain of E. coli O157:H7 in water samples taken from a canal in the Yuma growing region. WGS showed that the E. coli O157:H7 found in the canal water was closely related genetically to the E. coli O157:H7 isolated in ill people. Investigators believe this finding suggests that contaminated water coming into contact with produce, either through direct irrigation or other means, is a viable explanation for transmission of the bacteria to romaine lettuce. The FDA also notes that the canal is close to a Concentrated Animal Feeding Operation (CAFO), a facility that can hold in excess of 100,000 head of cattle at any one time. FDA traceback information showed a clustering of romaine lettuce farms nearby. The Environmental Assessment report will be made publicly when complete.[2]  

And a Bit(e) of Lettuce History

Date Vehicle Etiology Confirmed
July 1995 Leafy Greens E. coli O157:H7 74 1:MT
Sept. 1995 Romaine E. coli O157:H7 20 1:ID
Sept. 1995 Iceberg E. coli O157:H7 30 1:ME
Oct. 1995 Iceberg E. coli O157:H7 11 1:OH
May-June 1996 Mesclun Mix E. coli O157:H7 61 3:CT, IL, NY
May 1998 Salad Mix E. coli O157:H7 2 1:CA
Feb.-Mar. 1999 Iceberg E. coli O157:H7 72 1:NE
Oct. 1999 Salad E. coli O157:H7 92 3:OR, PA, OH
Oct. 2000 Lettuce E. coli O157:H7 6 1:IN
Nov. 2001 Lettuce E. coli O157:H7 20 1:TX
July-Aug. 2002 Romaine E. coli O157:H7 29 2:WA, ID
Nov. 2002 Lettuce E. coli O157:H7 13 1:Il
Dec. 2002 Lettuce E. coli O157:H7 3 1:MN
Oct. 2003-May 2004 Salad Mix E. coli O157:H7 57 1:CA
Apr. 2004 Spinach E. coli O157:H7 16 1:CA
Nov. 2004 Lettuce E. coli O157:H7 6 1:NJ
Sept. 2005 Romaine E. coli O157:H7 32 3:MN, WI, OR
Sept. 2006 Spinach E. coli O157:H7 and other serotypes 205 Multistate and Canada
Nov./Dec. 2006 Lettuce E. coli O157:H7 71 4:NY, NJ, PA, DE
Nov./Dec. 2006 Lettuce E. coli O157:H7 81 3:IA, MN, WI
July 2007 Lettuce E. coli O157:H7 26 1:AL
May 2008 Romaine E. coli O157:H7 9 1:WA
Oct. 2008 Lettuce E. coli O157:H7 59 Multistate and Canada
Nov. 2008 Lettuce E. coli O157:H7 130 Canada
Sept. 2009 Lettuce: Romaine or Iceberg E. coli O157:H7 29 Multistate
Sept. 2009 Lettuce E. coli O157:H7 10 Multistate
April 2010 Romaine E. coli O145 33 5:MI, NY, OH, PA, TN
Oct. 2011 Romaine E. coli O157:H7 58 Multistate
April 2012 Romaine E. coli O157:H7 28



June 2012 Romaine E. coli O157:H7 52 Multistate
Sept. 2012 Romaine E. coli O157:H7 9 1:PA
Oct. 2012 Spinach and Spring Mix Blend E. coli O157:H7 33 Multistate
Apr. 2013 Leafy Greens E. coli O157:H7 14 Multistate
Aug. 2013 Leafy Greens E. coli O157:H7 15 1:PA
Oct. 2013 Ready-To-Eat Salads E. coli O157:H7 33 Multistate
Apr. 2014 Romaine E. coli O126 4 1:MN
Apr. 2015 Leafy Greens E. coli O145 7 3:MD, SC, VA
June 2016 Mesclun Mix E. coli O157:H7 11 3:IL, MI, WI
Nov. 2017 Leafy Greens E. coli O157:H7 67 Multistate and Canada
Mar. 2018 Romaine E. coli O157:H7 219 Multistate and Canada


[1] https://www.canada.ca/en/public-health/services/public-health-notices/2018/public-health-notice-outbreak-e-coli-infections-linked-romaine-lettuce.html

[2] https://www.cdc.gov/ecoli/2018/o157h7-04-18/0; and https://www.fda.gov/Food/RecallsOutbreaksEmergencies/Outbreaks/ucm604254.htm