FDA Update on Traceback Related to the E. coli O157:H7 Outbreak Linked to Romaine Lettuce

Posted on May 31, 2018 by FDA Voice

By: Scott Gottlieb, M.D., and Stephen Ostroff, M.D.

The FDA continues to investigate the outbreak of E. coli O157:H7 infections associated with romaine lettuce from the Yuma growing region. Any contaminated product from the Yuma growing region has already worked its way through the food supply and is no longer available for consumption. So any immediate risk is gone. However, the FDA is committed to investigating the source of the outbreak and working with industry to help prevent similar events in the future.

Scott Gottlieb, M.D., Commissioner of the U.S. Food and Drug Administration

This is a serious and tragic outbreak. And we’re devoting considerable effort to identifying the primary source. We’ve made progress in recent weeks toward this goal. This outbreak of E. coli O157:H7 illnesses is the largest in the United States in more than 10 years. As of today, it has affected 172 persons in 32 states, and it is anticipated the numbers will be updated on Friday. Tragically, 45 percent of these ill people have been hospitalized, and one has died. And 20 of these people have developed hemolytic uremic syndrome (HUS), one of the most serious complications that can occur with E. coliO157:H7 infection.

These statistics reflect the severity of this particular foodborne illness. The kidney damage that’s associated with HUS can require temporary dialysis and the kidneys may never fully recover. For these reasons, anytime outbreaks caused by this pathogen occur, we need to find the root cause of the contamination and determine what went wrong. We need to relay these findings to industry so that measures can be put in place to prevent it from happening again.

The FDA’s investigators are actively searching for answers as to the source of this outbreak, and what steps can be taken to prevent it from recurring in future growing seasons. In the current outbreak, illness has generally been linked to the consumption of chopped romaine lettuce. The lettuce was generally consumed at restaurants or purchased at markets. In one cluster of illnesses at an Alaska correctional facility, the prison received and served whole head romaine lettuce rather than chopped and bagged romaine.

The FDA and our state partners have been involved in extensive traceback efforts of the romaine lettuce that was likely consumed by those who became ill. Traceback involves working backwards from the point of consumption or purchase of the product through the supply chain. It often includes investigating the multiple steps along the way. These steps can include suppliers, distributors and processors where the lettuce was chopped and bagged, and then back to the farm or farms that could have grown the lettuce that ended up in those bags. It’s a labor-intensive task. It requires collecting and evaluating thousands of records; and trying to accurately reproduce how the contaminated lettuce moved through the food supply chain to grocery stores, restaurants and other locations where it was sold or served to the consumers who became ill.

Stephen Ostroff, M.D., FDA’s Deputy Commissioner for Foods and Veterinary Medicine

Our traceback efforts are designed to find points of convergence from several well identified clusters of illness with a common point of exposure, such as a restaurant or grocery store. This means that as we draw lines for each cluster from one point in the supply chain to another point, we look for places where the lines will intersect and lead back to a common location. This can then help clarify where the contamination may have taken place.

We usually do this for clusters of ill individuals that occurred in different parts of the country; since lettuce in one part of the country may not follow the same pathway as lettuce in another part of the country. When that point of convergence is identified, efforts can then focus on how the contamination occurred at that location.

We’ve conducted traceback activities for many of the illnesses identified in this outbreak. We’ve used this information to create a traceback diagram that we’re releasing today. The diagram does not include tracebacks for all 172 cases. Rather, it focuses on settings where there were several well-documented clusters of cases. As additional traceback information is received, we anticipate the diagram will be updated.

Redacted draft traceback diagram for FDA investigation of multistate outbreak of E. coli O157:H7 infections linked to romaine lettuce from Yuma growing region.

As can be seen in the diagram, in the current outbreak, and based on the information we have to date, there are still no obvious points of convergence along the supply chain. There is only one straight line back to a single farm. And that particular instance involves the whole head lettuce served in the Alaska correctional facility, since it was not processed and was not mixed with lettuce from multiple farms, as seen in other parts of the traceback.

In these other tracebacks in the diagram, there are different suppliers, distributors and/or processors. These pathways lead back to different farms, sometimes many farms, where possibly contaminated lettuce could have been harvested during the timeframe of interest. The only point of commonality in our traceback efforts to date is that all of the farms are located in the Yuma growing region. This region is where a large portion of the romaine lettuce supply in the United States comes from during the winter months.

What does this traceback diagram tell us?

It says that there isn’t a simple or obvious explanation for how this outbreak occurred within the supply chain. If the explanation was as simple as a single farm, or a single processor or distributor, we would have already figured that out. The traceback diagram does show us that the contamination with E. coli O157:H7 was unlikely to have happened near the end of the supply chain (such as at a distributor) because there are no common distributors among the places that received and sold or served contaminated lettuce. The contamination likely happened at, or close to, the Yuma growing area.

Our task now is to investigate what happened. We are actively evaluating a number of theories about how romaine lettuce grown on multiple farms in the same growing region could have become contaminated around the same time. It’s possible that contamination occurred on multiple farms at once, through some sort of environmental contamination (e.g., irrigation water, air/dust, water used for pesticide application, animal encroachment). Another possibility is that it happened just after the lettuce left the farm. We are examining all possibilities and as we investigate we learn more about a potential common source we will communicate this information with growers and consumers. But the source and mode of contamination may remain difficult to identify.

Our efforts are complicated by the fact that romaine lettuce is a perishable commodity with a short shelf life of a couple of weeks. None of the lettuce that likely made people sick was available for testing because of the time between the incubation period of E. coli O157:H7 (the time between exposure to the lettuce and the onset of illness) and the time it takes to seek health care and collect specimens from ill people, test those specimens, report the illnesses to public health officials, fingerprint the pathogen to make sure it is part of the outbreak, and interview the ill people to identify where and when they were exposed. By that time, the lettuce they ate which could have made them ill is long gone.

Similarly, the lettuce growing and harvesting season in the Yuma growing region was essentially over by the time the outbreak was recognized in April, and harvesting has since ceased. That is why we, and our colleagues at the Centers for Disease Control and Prevention, have said that there’s no longer any romaine lettuce from the Yuma growing region available for purchase or consumption.

Romaine lettuce production in this area is now idle until later in the year. This makes it difficult to find places where the E. coli O157:H7 organism that caused the outbreak may have been hiding.

We have no evidence that romaine lettuce from other growing regions have been a part of this outbreak.

The FDA is looking at all possibilities for how the contamination may have caused such a large outbreak. This work will continue. In these efforts, we’re collaborating with outside experts who may have insights, ideas, or suggestions. This includes working with farmers, technical experts, the lettuce processing industry, state partners, and others. It also includes on-site assessments. Through such assessments we may be able to find a possible explanation so that steps can be taken to prevent this problem from recurring.

We’re committed to these efforts, and finding the root cause of this outbreak.

Romaine lettuce is one of the most popular types of lettuce in this country. We want American consumers to be confident in the quality and safety of the lettuce they consume. In addition to working to identify the source and mode of contamination, we will also continue working after the outbreak to evaluate what happened and how lessons learned can be used to provide feedback to industry on best practices and areas to work on. These include better tools to more efficiently and swiftly traceback commodities like lettuce through the supply chain, and better ways to standardize record keeping. We also want to explore the use of additional tools on product packaging that could improve traceability. For example, could QR codes be used to provide additional information that could help consumers more easily identify which lettuce should be avoided and which lettuce is ok to eat?

We’re also working with the leafy greens industry and technical experts to explore methods to grow and process lettuce in ways that further reduce the risk of outbreaks. We live in an era of unprecedented innovation and technology, and we want to bring more of that innovation and technology to bear to help solve this problem and ensure consumer confidence in healthy fruits and vegetables.

Food safety is one of the highest priorities at the FDA. This outbreak is a clear illustration of why that’s the case. It shows the terrible consequences when something goes wrong.

This outbreak marks the importance of moving forward with the Food Safety Modernization Act’s Produce Safety Rule. That rule is designed to implement practical measures to prevent contamination of fruits and vegetables at the farm. This rule is being implemented in close collaboration with our state partners and with our federal partners at the U.S. Department of Agriculture.

State partners will do the vast majority of routine inspections under the Produce Safety Rule. They are often the most familiar with their farming communities and growing and harvest practices. These inspections are slated to begin next year. We’re currently in the process of finalizing the guidance and training farmers throughout the country and those who ship produce to the U.S. on the rule’s requirements.

We believe that the measures outlined by the Produce Safety Rule, when fully implemented, will reduce the chance of an outbreak similar to the one we just experienced. That’s our goal, and our commitment, to the American public.

Scott Gottlieb, M.D., is Commissioner of the U.S. Food and Drug Administration

Stephen Ostroff, M.D., is FDA’s Deputy Commissioner for Foods and Veterinary Medicine

Follow Commissioner Gottlieb on Twitter @SGottliebFDA