US tomato outbreak, the facts
June 10, 2008
What’s going on with tomatoes? Reports from the FDA and CDC (to date) indicate:
- 167 228 552 613 756 869 922 1017 1090 1148 confirmed cases of Salmonella Saintpaul poisoning from contaminated raw tomatoes
- At least 23 25 48 53 69 95 107 111 203 210 220 hospitalizations have been reported.
- 2 deaths are believed to be associated with the outbreak.
- 17 23 28 30 34 36 40 41 42 states involved. Texas has the largest number of cases with 131 384 people affected while Ilinois had 34 100, followed by New mexico New Mexico at 70 98.
- Illnesses began between April 16 and May 27.
- Patients range in age from 1 to 82 years; 49% are female
- The U.S. Centers for Disease Control and Prevention estimates that for every salmonella case reported, 38 are not brought to the attention of physicians.
Only 3 persons infected with this strain of Salmonella Saintpaul were identified in the US during the same period in 2007. The previous rarity of this strain and the distribution of illnesses in all US regions suggest that the implicated tomatoes are distributed throughout much of the country. Because of inherent delays in reporting and because many persons with Salmonella illness do not have a stool specimen tested, it is likely many more illnesses have occurred than those reported. Some of these unreported illnesses may be in states not previously reported.
What’s causing the contamination?
According to the FDA, it has “not yet identified the source of the contaminated tomatoes. FDA recognizes that the source of the contaminated tomatoes may be limited to a single grower or packer in a specific geographic area and is working diligently with the states, the Centers for Disease Control and Prevention (CDC), and the Indian Health Service, and various food-industry trade associations to quickly determine the source of the tomatoes associated with the outbreak.”
No small problem
Since 1990, at least 12 large, multi-state foodborne outbreaks and some small local outbreaks have been associated with different varieties of tomatoes. Tomato-associated Salmonella outbreaks reported to CDC have increased in frequency and magnitude in recent years and caused 1,616 reported illnesses in nine outbreaks during 1990–2004, representing approximately 60,000 illnesses when accounting for the estimated proportion (97.5%) of unreported illness.
From 1998 – 2006, outbreaks reported to FDA associated with tomatoes made up 17 percent of the produce-related outbreaks. Salmonella has been the pathogen of concern most often associated with outbreaks from tomatoes.
The outbreaks linked to tomatoes over the last decade prompted the US Food and Drug Administration (FDA) to announce a “Tomato Safety Initiative” in 2007. The goal of the multi-year initiative was to explore contamination causes and develop better guidance to reduce the number of tomato-related illnesses. Officials were to focus on irrigation water, wells, chemical mixing procedures, droughts and floods, and animal proximity to growing fields, the FDA said.
In 1990 and 1993, investigations of multistate salmonellosis outbreaks traced the cause to tomatoes processed at a single South Carolina tomato packer. The authors, who published their findings in a 1999 issue of Epidemiology and Infection, concluded that inadequately monitored chlorine levels in the processor’s wash tanks likely contributed to the outbreaks.
Craig Hedberg, PhD, lead author of the study and a University of Minnesota expert on foodborne disease, said that despite investments that have been made to address tomato contamination problems over the past decade, little fundamental change has occurred. Hedberg said he hopes the FDA’s initiative will spur new measures to reduce the number of outbreaks linked to tomatoes.
The CDC says more research is needed to determine if Salmonella can travel from the roots to the fruit or if contaminated seeds can affect subsequent generations of tomato plants, the authors noted. “Understanding the mechanism of contamination and amplification of contamination of large volumes of tomatoes is critical to prevent large-scale, tomato-associated outbreaks,” they wrote.
The authors pointed out that produce packing houses were exempt from Good Manufacturing Practices (GMP) requirements, though the FDA encouraged GMP controls for water used in the packing houses. “However, the extent to which FDA guidance has been adopted by the industry is unknown,” the report said.
At a Mar 20, 2007 FDA hearing on regulatory options for fresh fruits and vegetables, Elisa Odabashian, director of the Consumers Union’s West Coast office, asserted that the FDA’s voluntary guidelines for producers have failed to make food safer, according to a copy of the prepared testimony. She said the only way to make food safer and rebuild consumer confidence is for the FDA and/or the California Department of Health Services to mandate Good Agricultural Practices for growers and Hazard Analysis/Critical Control Point (HACCP) systems for all processors.
Salmonella can enter tomato plants through roots or flowers and can enter the tomato fruit through small cracks in the skin, the stem scar, or the plant itself. However, whether Salmonella can travel from roots to the fruit, or if seeds can contaminate subsequent generations of tomato plants, is unknown. Understanding the mechanism of contamination and amplification of contamination of large volumes of tomatoes is critical to prevent large-scale, tomato-associated outbreaks. Contamination might occur during multiple steps from the tomato seed nursery to the final kitchen. Eradication of Salmonella from the interior of the tomato is difficult without cooking, even if treated with highly concentrated chlorine solution.