Factors contributing to decline in foodborne disease outbreak reports, United States

Foodborne illness outbreaks linked to unpasteurised milk and relationship to changes in state laws - United States, 1998-2018

Consumption of unpasteurised milk in the United States has presented a public health challenge for decades because of the increased risk of pathogen transmission causing illness outbreaks. We analysed Foodborne Disease Outbreak Surveillance System data to characterise unpasteurised milk outbreaks. Using Poisson and negative binomial regression, we compared the number of outbreaks and outbreak-associated illnesses between jurisdictions grouped by legal status of unpasteurised milk sale based on a May 2019 survey of state laws. During 2013-2018, 75 outbreaks with 675 illnesses occurred that were linked to unpasteurised milk; of these, 325 illnesses (48%) were among people aged 0-19 years. Of 74 single-state outbreaks, 58 (78%) occurred in states where the sale of unpasteurised milk was expressly allowed. Compared with jurisdictions where retail sales were prohibited (n = 24), those where sales were expressly allowed (n = 27) were estimated to have 3.2 (95% CI 1.4-7.6) times greater number of outbreaks; of these, jurisdictions where sale was allowed in retail stores (n = 14) had 3.6 (95% CI 1.3-9.6) times greater number of outbreaks compared with those where sale was allowed on-farm only (n = 13). This study supports findings of previously published reports indicating that state laws resulting in increased availability of unpasteurised milk are associated with more outbreak-associated illnesses and outbreaks.

Temporal changes in the proportion of Salmonella outbreaks associated with 12 food commodity groups in the United States

Using data from 20 years of Salmonella foodborne outbreaks, this study investigates significant trends in the proportion of outbreaks associated with 12 broad commodity groups. Outbreak counts are demonstrated to have a stronger trend signal than outbreak illness counts. The number of outbreaks with an identified food vehicle increased significantly between 1998 and 2000. This was followed by a 10-year period when the number of outbreaks decreased. The number of outbreaks increased significantly between 2010 and 2014 and then remained unchanged for the remainder of the study period. During the period of 1998 through 2017, the proportion of outbreaks for three commodities groups, consisting of eggs, pork and seeded vegetables, changed significantly. No significant changes were observed in the remaining nine commodity groups. Simple approximations are derived to highlight the effect of dependencies between outbreak proportions and a consumption analysis for meat and poultry is used to enhance the limited interpretability of the changes in these proportions. Given commodity-specific approaches to verifying food safety and promoting pathogen reduction, regulatory agencies benefit from analyses that elucidate illness trends attributable to the products under their jurisdiction. Results from this trend analysis can be used to inform the development and assessment of new pathogen reduction programmes in the United States.

Microbial and physicochemical assessment of irrigation water treatment methods

AIMS

The presence of foodborne pathogens in preharvest agricultural water has been identified as a potential contamination source in outbreak investigations, driving markets and auditing bodies to begin requiring water treatment for high-risk produce. Therefore, it is essential that we identify water treatment methods which are effective as well as practical in their application on farm.

METHODS AND RESULTS

In this work, we evaluated two sanitizers which are most prominent in preharvest agricultural water treatment (calcium hypochlorite (free chlorine: 3-5 ppm) and peracetic acid (PAA: 5 ppm)), an EPA registered antimicrobial device (ultraviolet light (UV)), in addition to a combination approach (chlorine + UV, PAA + UV). Treatments were evaluated for their ability to inactivate total coliforms and generic Escherichia coli and consistency in treatment efficacy over 1 h of operation. Physicochemical variables were measured along with microbial populations at 0, 5, 15, 30, 45 and 60 min of operation. Escherichia coli and coliform counts showed a significant (P < 0·05) reduction after treatment, with combination and singular treatments equally effective at inactivating E. coli and coliforms. A significant increase (P < 0·05) in oxidation-reduction potential was seen during water treatment (Chlorine; UV + Chlorine), and a significant reduction (P < 0·05) in pH was seen after PAA and PAA + UV treatments (60 min).

CONCLUSION

Overall, the results indicate that all treatments evaluated are equally efficacious for inactivating E. coli and coliforms present in surface agricultural water.

SIGNIFICANCE AND IMPACT OF THE STUDY

This information when paired with challenge studies targeting foodborne pathogens of interest can be used to support grower decisions when selecting and validating a preharvest agricultural water treatment programme.

Produce-associated foodborne disease outbreaks, USA, 1998-2013

The US Food Safety Modernization Act (FSMA) gives food safety regulators increased authority to require implementation of safety measures to reduce the contamination of produce. To evaluate the future impact of FSMA on food safety, a better understanding is needed regarding outbreaks attributed to the consumption of raw produce. Data reported to the US Centers for Disease Control and Prevention's Foodborne Disease Outbreak Surveillance System during 1998-2013 were analysed. During 1998-2013, there were 972 raw produce outbreaks reported resulting in 34 674 outbreak-associated illnesses, 2315 hospitalisations, and 72 deaths. Overall, the total number of foodborne outbreaks reported decreased by 38% during the study period and the number of raw produce outbreaks decreased 19% during the same period; however, the percentage of outbreaks attributed to raw produce among outbreaks with a food reported increased from 8% during 1998-2001 to 16% during 2010-2013. Raw produce outbreaks were most commonly attributed to vegetable row crops (38% of outbreaks), fruits (35%) and seeded vegetables (11%). The most common aetiologic agents identified were norovirus (54% of outbreaks), Salmonella enterica (21%) and Shiga toxin-producing Escherichia coli (10%). Food-handling errors were reported in 39% of outbreaks. The proportion of all foodborne outbreaks attributable to raw produce has been increasing. Evaluation of safety measures to address the contamination on farms, during processing and food preparation, should take into account the trends occurring before FSMA implementation.

Fish-Associated Foodborne Disease Outbreaks: United States, 1998-2015

Each year in the United States, ∼260,000 people get sick from contaminated fish. Fish is also the most commonly implicated food category in outbreaks. We reviewed the Centers for Disease Control and Prevention Foodborne Disease Outbreak Surveillance System for outbreaks resulting from consumption of fish during the period 1998-2015. We found 857 outbreaks associated with fish, resulting in 4815 illnesses, 359 hospitalizations, and 4 deaths. The median number of illnesses per outbreak was three (range: 2-425). The annual number of fish-associated outbreaks declined from an average of 62 per year during the period 1998-2006 to 34 per year during the period 2007-2015. Hawaii (221 outbreaks [26%]) and Florida (203 [24%]) reported the most outbreaks. Among 637 outbreaks (74%) with a confirmed etiology, scombrotoxin (349 [55%]) and ciguatoxin (227 [36%]) were by far most common. Most outbreak-associated illnesses were caused by scombrotoxin (1299 [34%]), Salmonella (978 [26%]), and ciguatoxin (894 [23%]). Most hospitalizations were caused by Salmonella (97 [31%]) and ciguatoxin (96 [31%]). Norovirus (105 average illnesses; range: [6-380]) and Salmonella (54 [3-425]) caused the largest outbreaks. Fish types implicated most often were tuna (37%), mahi-mahi (10%), and grouper (9%). The etiology-fish pairs responsible for the most outbreaks were scombrotoxin and tuna (223 outbreaks), scombrotoxin and mahi-mahi (64), and ciguatoxin and grouper (54). The pairs responsible for the most illnesses were scombrotoxin and tuna (720 illnesses) and Salmonella and tuna (660). Of the 840 outbreaks (98%) with a single location of food preparation, 52% were associated with fish prepared in a restaurant and 33% with fish prepared in a private home. Upstream control measures targeted to the most common etiologies and controls during processing and preparation could further reduce outbreaks caused by fish.

Epidemiology of restaurant-associated foodborne disease outbreaks, United States, 1998-2013

Although contamination of food can occur at any point from farm to table, restaurant food workers are a common source of foodborne illness. We describe the characteristics of restaurant-associated foodborne disease outbreaks and explore the role of food workers by analysing outbreaks associated with restaurants from 1998 to 2013 reported to the Centers for Disease Control and Prevention's Foodborne Disease Outbreak Surveillance System. We identified 9788 restaurant-associated outbreaks. The median annual number of outbreaks was 620 (interquartile range 618-629). In 3072 outbreaks with a single confirmed aetiology reported, norovirus caused the largest number of outbreaks (1425, 46%). Of outbreaks with a single food reported and a confirmed aetiology, fish (254 outbreaks, 34%) was most commonly implicated, and these outbreaks were commonly caused by scombroid toxin (219 outbreaks, 86% of fish outbreaks). Most outbreaks (79%) occurred at sit-down establishments. The most commonly reported contributing factors were those related to food handling and preparation practices in the restaurant (2955 outbreaks, 61%). Food workers contributed to 2415 (25%) outbreaks. Knowledge of the foods, aetiologies, and contributing factors that result in foodborne disease restaurant outbreaks can help guide efforts to prevent foodborne illness.

Foodborne Outbreaks Reported to the U.S. Food Safety and Inspection Service, Fiscal Years 2007 through 2012

The U.S. Department of Agriculture's Food Safety and Inspection Service (FSIS) works closely with federal, state, and local public health partners to investigate foodborne illness outbreaks associated with its regulated products. To provide insight into outbreaks associated with meat and poultry, outbreaks reported to FSIS during fiscal years 2007 through 2012 were evaluated. Outbreaks were classified according to the strength of evidence linking them to an FSIS-regulated product and by their epidemiological, etiological, and vehicle characteristics. Differences in outbreak characteristics between the period 2007 through 2009 and the period 2010 through 2012 were assessed using a chi-square test or Mann-Whitney U test. Of the 163 reported outbreaks eligible for analysis, 89 (55%) were identified as possibly linked to FSIS-regulated products and 74 (45%) were definitively linked to FSIS-regulated products. Overall, these outbreaks were associated with 4,132 illnesses, 772 hospitalizations, and 19 deaths. Shiga toxin-producing Escherichia coli was associated with the greatest proportion of reported outbreaks (55%), followed by Salmonella enterica (34%) and Listeria monocytogenes (7%). Meat and poultry products commercially sold as raw were linked to 125 (77%) outbreaks, and of these, 105 (80%) involved beef. Over the study period, the number of reported outbreaks definitively linked to FSIS-regulated products (P = 0.03) declined, while the proportion of culture-confirmed cases (P = 0.0001) increased. Our findings provide insight into the characteristics of outbreaks associated with meat and poultry products.