Salmonella causes more than 1 million foodborne illnesses every year.1 It is responsible for more hospitalizations and deaths than any other type of bacterium or virus found in food, and its health-related costs to the nation run as much as $11 billion a year.2 Food is estimated to be the source of 90 percent of all salmonella infections, and contaminated poultry is believed to be a main culprit.3,4
A multistate outbreak of Salmonella Heidelberg infections linked to ground turkey in 2011 sickened 136 people, causing 37 hospitalizations and one death. The Pew Charitable Trusts' analysis of the outbreak found numerous inadequacies in the foodborne illness surveillance system that, if addressed, could help to prevent illnesses and, in some cases, deaths.
An examination of the timeline for the outbreak reveals that the U.S. Centers for Disease Control and Prevention (CDC) and the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS) did not identify the contaminated food source—ground turkey processed at one of Cargill Meat Solutions Corp.'s plants — until 22 weeks after the first person became ill and 10 weeks after CDC detected the outbreak. Cargill's subsequent recall of approximately 36 million pounds of ground turkey products is one of the nation's biggest poultry recalls.
The 2011 Salmonella Heidelberg outbreak linked to ground turkey deserves special scrutiny because it highlights several opportunities to improve foodborne illness surveillance, detection, and response. Pew's examination of this outbreak focuses on three problems in the system as it currently exists:
1. Infections from salmonella are not given enough attention by the public health system and, as a result:
- Public health officials do not always interview patients promptly, missing a critical opportunity
to obtain the most accurate information on what they have eaten. In addition, a common set of questions is not used, making it difficult to aggregate and analyze key information.
- Not all states require that samples of salmonella cultured from patients (“isolates”) by clinical
laboratories be sent to public health laboratories for further analysis.
- Public health labs do not perform DNA fingerprinting of salmonella isolates received on a universal
or timely basis.
2. Bacteria isolated from retail meat and poultry samples and uploaded onto PulseNet — a national network of labs that shares information on foodborne bacteria — are not identified with the names of the brand and processing plants that produced the samples, nor by their purchase dates.i This is the case for other foodborne pathogens, not just salmonella. Delays in the resolution of outbreaks may occur because investigators who rely on PulseNet to find matches of bacteria in humans and other sources do not have ready access to this identifying information. In addition, without these data, there is no ability to detect when a plant repeatedly produces contaminated products.
3. Government officials often wait until they are relatively certain of a likely source of an outbreak before notifying a company that it may have produced the contaminated food. Waiting for certainty in the 2011 ground turkey case resulted in an outbreak lasting months when, with earlier food industry input, it might have been resolved much sooner and thereby prevented many illnesses.
Based on its analysis, Pew makes three general recommendations for improving salmonella outbreak detection and response. These recommendations could inform the CDC’s charge under Section 205 of the 2011 FDA Food Safety Modernization Act to evaluate how to "enhance foodborne illness surveillance systems."
1. Federal and state officials should make the detection of and response to salmonella outbreaks a
priority by enhancing the surveillance system for these bacteria so that:
- State and local public health officials interview patients as soon as their cases are reported, using a
common set of questions to capture data vital to the outbreak investigation.
- All states require clinical labs to submit their salmonella isolates to public health laboratories.
- Public health labs quickly conduct DNA fingerprinting for all salmonella isolates they receive.
2. The U.S. Food and Drug Administration (FDA) should modify the retail arm of the National Antimicrobial
Resistance Monitoring System (NARMS) so that it can be used to help detect and respond to outbreaks. Specifically, FDA should require that information on the brand, processing plant, and purchase date for meat and poultry retail samples be included when the DNA fingerprint of bacteria isolates are uploaded to PulseNet. Moreover, the DNA fingerprints should be uploaded more quickly.
3. FDA, FSIS, CDC, and state authorities must develop a mechanism that facilitates engagement with food companies in the early stages of an outbreak investigation when information, such as production schedules and distribution patterns, could speed identification of contaminated foods.
Pew's recommendations for surveillance improvements target key points in this outbreak investigation in which existing policies and practices resulted in unnecessary delays and preventable illnesses. While resource constraints could make these recommendations difficult for some states to achieve, in light of the staggering health-related costs of foodborne illnesses, stopping outbreaks as soon as possible will save money and protect the public.
i - The samples are originally collected under the retail arm of the National Antimicrobial Resistance Monitoring System, a national public health surveillance system that tracks antibiotic resistance in foodborne bacteria. The NARMS program was established in 1996 as a partnership between the U.S. Food and Drug Administration, the Centers for Disease Control and Prevention, and the U.S. Department of Agriculture. NARMS monitors antimicrobial susceptibility among enteric bacteria from humans, retail meats, and food animals.