Each year, foodborne illness outbreaks receive extensive media coverage. Typically, the outbreaks that make the headlines are multi-state outbreaks where a group of local, state, and federal public health officials jointly investigate, with federal officials often taking the lead. Each day, state and local officials investigate dozens of intrastate outbreaks with the same level of professionalism and dedication as with a multi-state outbreak. While sometimes these outbreaks are smaller, they still result in significant impact on individuals and communities. This article highlights the work, innovation, and dedication of local and state outbreak investigators in their localized health and agriculture agencies. The innovation and ingenuity at the state and local levels lead to advancements in outbreak investigations on the national level. Even in a multi-state outbreak, these state and local officials are the boots on the ground, providing the information needed to coordinate the national investigation.
An outbreak investigation requires an interdisciplinary approach often referred to as a three-legged stool. Critical for a successful outbreak investigation, the three essential disciplines are environmental health, epidemiology, and laboratory services (see “Essential Disciplines”). Each outbreak investigation is different and may require a different level of effort from each discipline. Successfully investigating outbreaks requires strong programs in each of the three disciplines.
This article will focus on outbreak investigations in three states: Washington, Tennessee, and New York. Each investigation has its own unique nuisances and challenges, but there are themes across the outbreaks, including the use of environmental sampling to determine whether relationships exist between the pathogens found in ill individuals and in the environment of the suspected source. Whole-genome sequencing (WGS) has also become an essential tool in outbreak investigations, assisting in determining how closely genetically related pathogens are. This helps investigators determine the likely source of an outbreak and whether cases appear to be linked. Further, the federal government through the U.S. Centers for Disease Control and Prevention (CDC) and the U.S. Food and Drug Administration (FDA) assist with financial support for state and local outbreak investigations through a variety of funding instruments (see “Programs That Assist State and Local Governments in Outbreak Investigations”).
Washington RRT: Creating Collaborations to Link Illnesses and Adulterated Product across Time
Washington State has developed and continually improved their food and feed Rapid Response Team (RRT) since 2009. As one of the original states to receive FDA cooperative agreement funding, Washington has worked hard to create a flexible, capable response team to effectively mitigate public health threats associated with human and animal food. The Rapid Response Program, housed within the Washington State Department of Agriculture (WSDA), maintains close collaborative relationships with the FDA Office of Human and Animal Foods Division 6-West (OHAF-6W), the Washington State Department of Health (WADOH), local health jurisdictions in Washington State, industry, and other key partners to help safeguard the food and feed supply.
One such capability of the Washington RRT is to quickly coordinate response partners and leverage their resources to link pathogens found in food samples to human illnesses at the genetic level. These illnesses may even be “historical” in nature in that they may have been reported months or years in the past. However, with stronger technologies and methods such as WGS and bioinformatics, these illnesses can now be associated with pathogens collected from current product and clinical samples to a high degree of accuracy. Linking such illnesses to samples collected during current RRT responses may allow responders to identify chronic issues at a food production facility such as a resident pathogen that is not being killed through current cleaning and sanitation procedures.
This type of “rapid response across time” was exemplified through a multi-agency response coordinated by the Washington RRT in September 2017. Eight months earlier, the WSDA Rapid Response Program was notified by foodborne illness epidemiologists at WADOH that two human Salmonella Dublin cases with indistinguishable pulsed-field gel electrophoresis (PFGE) patterns and similar illness onset dates had reported consuming retail raw milk from a specific licensed raw milk dairy in Washington State. With proper licensing through WSDA, retail raw milk and hand-skimmed raw cream are legal in Washington State. Approximately 32 firms were licensed to produce and distribute these raw dairy products within the state’s borders as of December 2018.
Subsequent sampling of the finished raw milk product processed by the dairy in question did not indicate the presence of Salmonella, but rather Shiga toxin-producing Escherichia coli. Based on these lab results, the dairy decided to voluntarily recall the implicated lots of their organic retail raw milk in February 2017.
Fast-forwarding to September 2017, routine surveillance sampling conducted by WSDA subsequently confirmed results for the presence of Salmonella spp. in retail raw milk product processed by the same firm. This time around, the firm respectfully declined to issue a voluntary recall. Due to the possible public health implications based on the positive sample results, WSDA developed and distributed a public health alert, a public information release that includes the sample results, health information on salmonellosis, and distribution information for the positive product.
Through coordination efforts led by the Washington RRT, the WADOH Food Safety Program notified local health jurisdictions throughout the state and provided them with a copy of the alert to be used as a tool for notifying retail points of sale.
After the four additional raw milk samples were confirmed for the presence of Salmonella spp., Washington RRT was notified by WADOH epidemiologists that serology identified the pathogens as Salmonella Dublin. PFGE patterns were also indistinguishable from both the previous product samples and the two human Salmonella Dublin cases back in January 2017. The association between a historical illness cluster and a food product was getting stronger.
With this tie between confirmed positive product samples and historical human illnesses, WADOH issued their own public information in collaboration with WSDA. The release stated that health officials urged consumers not to drink the organic retail raw milk with the implicated sell-by dates from the specific dairy. Shortly thereafter, WSDA issued a summary suspension of the dairy’s milk processing plant license, therefore administratively halting the ability to legally process and distribute retail raw milk. The dairy’s milk producer licenses were not affected by the order, which allowed the dairy to still milk their cows, hold their milk, and divert it to be pasteurized if they chose to do so.
Additionally, Washington RRT and WADOH epidemiologists requested CDC bioinformatics to conduct a genomic comparison of the Dublin isolates. The comparison indicated that all seven samples (five product and two clinical) were highly related to one another within 0–2 single nucleotide polymorphisms.
Leveraging the capabilities of its public health partners and the current gold standard in food safety-related DNA sequencing, Washington State was able to associate human illnesses with a food product and take regulatory steps to mitigate future illnesses. Working closely with the WSDA Food Safety Program, the dairy took specific corrective and preventive measures that hopefully will reduce the risk of product adulteration in the future.
Identifying the capabilities of its response partners and coordinating their deployment to protect public health is a key strength that the Washington RRT brings to an integrated food/feed safety system both within Washington State and nationally. Due to the proactive nature of the public health agencies in Washington State, the newest tools and resources can be effectively utilized to control current public health threats and prevent them from occurring in the future.
Getting to the Problem: Detection of Norovirus in Tennessee
Norovirus is the leading cause of foodborne illnesses in the U.S., with annual illnesses estimated in the millions, thousands of hospitalizations, and hundreds of deaths. The health and economic impacts are significant and keep this pathogen in the forefront of public health efforts. Recent advances in norovirus detection have allowed public health agencies to improve investigation techniques in outbreaks where norovirus is the culprit. Environmental sampling provides a valuable resource in these outbreaks, strengthening the connection between ill people, suspected foods, and environmental contamination.
Norovirus outbreak investigations typically involve three complementary areas: 1) environmental investigations, 2) epidemiological studies, and 3) laboratory analysis of clinical specimens. Sometimes these investigation methods are ineffective in determining etiology and mode of exposure due to people’s unwillingness to provide a sample, small sample size for statistical analyses, and/or poor food history recall. Environmental sampling, however, has helped during outbreak investigations with missing data or complemented outbreaks where data from other areas are strong. Environmental sampling for norovirus is a relatively new approach providing an additional tool to help fill informational gaps and aid in determining the cause of the outbreak, while facilitating short- and long-term control measures.
The Tennessee Department of Health (TNDOH) has worked alongside its public health lab to add this tool to its public health toolbox and has collaborated to develop new sampling protocols that include swabbing for norovirus during outbreaks at foodservice establishments (FSEs). The sampling technique and materials used were based on the environmental sampling protocol described in a recent study.[1] TNDOH has used a swab with a tip made from macrofoam—a material proven to be more effective in recovering norovirus from surfaces when compared with materials like cotton, nylon, and traditional sponges. Additionally, macrofoam has proven effective in releasing norovirus particles during the extraction process.
Since testing this strategy, TNDOH successfully detected norovirus in two restaurant outbreaks. In one of these outbreaks, the local health department was notified that a dining party had become ill with vomiting and diarrhea following meals at a restaurant (Table 1). Illness onset, symptoms, and duration were consistent with norovirus. This prompted an environmental assessment at the restaurant, where a food handler was identified as having diarrhea and being present at the restaurant during the period in question. The employee reported having a diarrheal episode in a single-occupancy, unisex restroom that was not used by any members of the dining party. Investigators used this information to determine likely contamination zones and collected 24 swabs in the ill food handler’s workstation, the restroom used by the ill food handler, the restrooms used by the dining party, and the private dining area (Table 2).
Epidemiological information for this outbreak was limited to the dining party. No additional ill or well customers outside the dining party were identified because customer contact information was not retained by the FSE. Therefore, definitive epidemiological studies could not be performed.
Stool specimens were collected from four out of the eight dining party members who reported illness. TNDOH could not obtain stool from the ill food handler. All stool specimens were positive for norovirus GII.2. Of the 24 swabs collected at the restaurant, two were positive for norovirus GII.2, the same genotype the ill customers had. Importantly, both positive samples were recovered from the same toilet area used by the ill chef who reported having diarrhea while working. All samples recovered from the restroom used exclusively by the dining party were negative.