What is an E. coli Outbreak?
An E. coli outbreak is an incident in which 2 or more cases of E. coli result from the same source. To determine if 2 or more people contracted E. coli from the same source, health officials conduct DNA fingerprinting of E. coli isolates from the victims’ stool samples. Health officials then compare the DNA fingerprints, looking for similarities. E. coli victims sickened by genetically similar E. coli bacteria contracted the E. coli from the same source.
E. coli outbreaks are often foodborne. Food can cause E. coli outbreaks when the food is contaminated internally or becomes contaminated during harvesting, processing, or preparation. When there is a foodborne E. coli outbreak, public health scientists use epidemiological, microbiological, and trace-back technologies to control the outbreak and remove the food from the distribution channels.
In some cases, an E. coli outbreak is linked to a restaurant, deli, or other establishment that serves food. Even if the food product that caused the illnesses is not found, victims of the E. coli outbreak can pursue a claim against the eating establishment. In a recent foodborne illness case handled by our firm, health officials linked the illness to a restaurant but could not pinpoint the food that caused the illness. Epidemiological evidence pointed to the source of the outbreak being one of several possible food items. Even so, we obtained a settlement for our clients.
To contact an E. coli lawyer at Pritzker | Ruohonen, please call toll-free at 1-888-377-8900 or submit the firm’s online consultation form.
What is FoodNet
FoodNet is a joint effort by the CDC, FDA, USDA, and state health departments to monitor trends in the occurence of foodborne illness. The CDC funds cooperative agreements with some state and local health departments to conduct population-based surveillance and research that go beyond the routine functions of health departments. There are currently sites in 10 states: California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon, and Tennessee.
The CDC FoodNet website lists the following as the objectives of the program:
- Determine the burden of foodborne illness in the United States
- Monitor trends in the burden of specific foodborne illness over time
- Attribute the burden of foodborne illness to specific foods and settings
- Develop and assess interventions to reduce the burden of foodborne illness
FoodNet monitors the occurrence of illness related to nine different pathogens: Campylobacter, Cyclospora, Cryptosporidium, E. coli (both O157:H7 and other strains of E. coli), Listeria monocytogenes, Salmonella, Shigella, Vibrio, and Yersinia enterocolitica. FoodNet also conducts hemolytic uremic syndrome (HUS) surveillance. HUS is an illness that can develop from an E. coli O157:H7 infection.
For each case of illness, FoodNet reviews the case and collects and analyzes strains. Special case-control studies are conducted across FoodNet sites in order to identify the major risk factors for sporadic illness, and community surveys are conducted to help determine the overall burden of foodborne illness.
E. coli Outbreaks and the CDC
The Center for Disease Control and Prevention (CDC) works with state and local health departments to conduct ongoing surveillance of cases of foodborne illness and to investigate disease outbreaks. The CDC uses both surveillance data and results of outbreak investigations to identify the factors responsible for illness so that immediate control measures can be taken and longer term prevention strategies can be developed. The CDC’s role in measuring the success of interventions is to see whether they translate into reductions in the incidence of human cases of foodborne illness.
Chronology of CDC Involvement in an E. coli Outbreak
- The first response in an E. coli outbreak is usually from the state or local health department.
- If the outbreak warrants, the state health department will invite the CDC to participate in the investigation. This is warranted if an outbreak is very large or significant, is thought to involve an unusual pathogen or unexpected food vehicle, affects multiple states or countries, or preliminary investigations do not reveal a source.
- The CDC, working with state and local health officials, combines laboratory diagnostic techniques and epidemiologic investigative methods to determine the causative agent of the illness, the food vehicle responsible for transmission, and the environmental factors that contributed to the outbreak.
- If a food is identified as the source of illness, the CDC collaborates with the FDA or USDA on the investigation and control of the outbreak, based upon which agency regulates the suspected food.
How Epidemiologists Uncovered the Spinach-E. coli Outbreak of 2006
In September of 2006 epidemiologists in Wisconsin identified several cases of E. coli O157:H7 that they suspected were associated with the consumption of fresh spinach. During this time, epidemiologists in Oregon noticed the same thing. The spinach-E. coli outbreak had begun. The following is a CDC-recount of events surrounding the spinach-E. coli outbreak of the fall of 2006 which sickened hundreds of people and resulted in at least 3 deaths:
On September 13, 2006, CDC officials were alerted by epidemiologists in Wisconsin and Oregon that fresh spinach was the suspected source of small clusters of Escherichia coli serotype O157:H7 infections in those states. On the same day, New Mexico epidemiologists contacted Wisconsin and Oregon epidemiologists about a cluster of E. coli O157:H7 infections in New Mexico associated with fresh spinach consumption. Wisconsin public health officials had first reported a cluster of E. coli O157:H7 infections to CDC on September 8. On September 12, CDC PulseNet had confirmed that the E. coli O157:H7 strains from infected patients in Wisconsin had matching pulsed-field gel electrophoresis (PFGE) patterns and identified the same pattern in patient isolates from other states. This report describes the joint investigation and outbreak-control measures undertaken by state public health officials, CDC, and the Food and Drug Administration (FDA). This investigation and additional case finding are ongoing.
As of September 26, a total of 183 persons infected with the outbreak strain of E. coli O157:H7 had been reported to CDC from 26 states (Figure 1). Among the ill persons, 95 (52%) were hospitalized, 29 (16%) had hemolytic uremic syndrome (HUS), and one person died. The deaths of two other patients possibly related to this outbreak are under investigation. Eighty-five percent of patients reported illness onset from August 19 to September 5 (Figure 2). Fresh spinach was identified as the source of the outbreak. One hundred twenty-three of 130 patients (95%) reported consuming uncooked fresh spinach during the 10 days before illness onset. In addition, E. coli O157:H7 with a PFGE pattern matching the outbreak strain has been isolated from three open packages of fresh spinach consumed by patients (one from New Mexico, one from Utah, and one from Pennsylvania).
On September 14, FDA advised consumers by press release and press conference to not eat bagged fresh spinach. On September 15, a California company that bags spinach under several brand names announced a voluntary recall of all fresh spinach-containing products. On September 16, FDA expanded its warning and advised consumers to not eat fresh spinach or fresh spinach-containing products. On September 21, FDA informed consumers that only spinach grown in three California counties (Monterey, San Benito, and Santa Clara) was implicated in the outbreak.
A confirmed case is defined as a culture-confirmed E. coli O157:H7 infection in a person residing in the United States, with illness onset from August 1 to the present (or, if date of onset is unknown, E. coli O157:H7 isolated from August 15 to the present) and a PFGE pattern identified by the XbaI restriction enzyme that matches the pattern of the outbreak strain. August 1 was selected as the earliest illness onset date in the case definition to ensure that the earliest cases in the outbreak were identified and investigated. However, the first six confirmed cases (with illness onsets during August 2–15) were in persons who did not report fresh spinach consumption during the week before illness onset. The first date that illness onset was reported by a person who recently consumed fresh spinach was August 19.
Infections with this outbreak strain of E. coli O157:H7 (one of 3,520 unique E. coli O157:H7 strains reported to CDC PulseNet since 1996) have been reported sporadically to CDC PulseNet since 2003 (an average of 21 cases per year during 2003–2005). This finding suggests the occasional presence of this strain in the environment and food supply; however, it has not been associated with a recognized outbreak in the past.
The time from illness onset to confirmation that a case of E. coli O157:H7 is part of an outbreak is typically 2–3 weeks, including the time required for an infected person to seek medical care and for health-care providers and public health officials to obtain a culture, transfer the bacterial culture to a public health laboratory, perform PFGE testing, and submit the PFGE pattern into the national database at CDC. In this outbreak, the average time from illness onset to PFGE pattern submission to the national database at CDC has been 15 days; additional information is available at http://www.cdc.gov/foodborne/ecolispinach/reportingtimeline.htm.
Parallel laboratory and epidemiologic investigations were crucial in identifying the source of this outbreak. Timely PFGE testing by state public health laboratories, PFGE pattern submission by states to CDC PulseNet, and analysis of PFGE patterns in the CDC PulseNet national database resulted in rapid detection of the outbreak. Concurrent collection of case exposure information by epidemiologists in affected states and sharing of exposure information among states and CDC led to rapid identification of the suspected food source and public health action.
Source: “Ongoing Multistate Outbreak of Escherichia coli serotype O157:H7 Infections Associated with Consumption of Fresh Spinach — United States, September 2006,” Morbidity and Mortality Weekly Report, September 29, 2006, Vol. 55, No. 38:1045-1046.
For information about E. coli, please see the following:
Pritzker | Ruohonen has a national practice and represents E. coli victims throughout the United States. To contact the firm, please call toll-free at 1-888-377-8900 or submit the online contact form.
Tracking an E. coli Outbreak: The Role of PulseNET
Each year hundreds of people are sickened by E. coli and about 60 die. Until fairly recently, it was difficult tracking an E. coli outbreak. The Centers for Disease control (CDC) now has a system of genetic fingerprinting for E. coli bacteria (and other foodborne bacteria) called PulseNET. Here is the CDC explaination of PulseNET:
PulseNet is a national network of public health and food regulatory agency laboratories coordinated by the Centers for Disease Control and Prevention (CDC). The network consists of: state health departments, local health departments, and federal agencies (CDC, USDA/FSIS, FDA).
PulseNet participants perform standardized molecular subtyping (or “fingerprinting”) of foodborne disease-causing bacteria by pulsed-field gel electrophoresis (PFGE). PFGE can be used to distinguish strains of organisms such as Escherichia coli O157:H7 (E. coli O157:H7), Salmonella, Shigella, Listeria, or Campylobacter at the DNA level. DNA “fingerprints,” or patterns, are submitted electronically to a dynamic database at the CDC. These databases are available on-demand to participants—this allows for rapid comparison of the patterns.
If someone goes to the doctor with symptoms of E. coli, a sample of the stool may be tested for E. coli bacteria. If E. coli bacteria is found, further testing may be needed to determine if the E. coli bacteria is E. coli O157:H7. If the stool samples test positive for E. coli O157:H7 or another virulent strain of E. coli bacteria, a culture of the E. coli bacteria may be sent to the CDC for genetic fingerprinting as part of the PulseNET system. Not every case of E. coli O157:H7 has this testing done. This is one reason why it is imperative that anyone diagnosed with E. coli contacts a lawyer immediately. At Pritzker | Ruohonen, we have a process for getting the needed testing done.
Each E. coli outbreak involves a genetically-unique E. coli bacteria. This means that the genetic fingerprint of the E. coli O157:H7 bacteria for one outbreak is genetically unique from the E. coli O157:H7 bacteria of a different outbreak. For example, in the fall of 2006, there were two E. coli outbreaks involving Mexican fast food restaurants, Taco Bell and Taco Johns. The CDC knew that these outbreaks were two, unrelated outbreaks because the genetic fingerprint of the E. coli O157:H7 involved in the Taco Bell outbreak was different from the E. coli O157:H7 in the Taco Johns outbreak.
Once the PulseNET system identifies an outbreak (generally two or more cases of E. coli with identical genetic fingerprints), epidemiologists interview the people who contracted the E. coli infections to try determine the source of the outbreak. Obviously, if the cases are children, people who are too sick to be interviewed, or people have died, family members and others are interviewed.
Pritzker | Ruohonen has a national practice and represents E. coli victims throughout the United States. To contact the firm, please call toll-free at 1-888-377-8900 or submit the online contact form.
