Beef products are one of the main sources of Shiga toxin-producing E. coli infections around the world, according to a report published by the FAO and WHO. Fresh produce was also a significant source.

The Food and Agriculture Organization of the United Nations (FAO) and World Health Organization (WHO) figures based on 2010 estimates show STEC infections cause more than 1 million illnesses and 128 deaths annually.

The report analysed data from global STEC foodborne outbreak investigations, as well as a systematic review and meta-analysis of case-control studies of sporadic infections for all dates and locations.

It concluded that prioritizing interventions for control on beef supply chains may provide the largest return on investment when implementing strategies for STEC control.

Food sources of STEC
A total of 957 STEC outbreaks from 27 countries covering 1998 to 2017 were included. Data identified that 16 percent of outbreaks were attributed to beef, 15 percent to produce including fruits and vegetables, and 6 percent to dairy products.

However, food sources involved in 57 percent of outbreaks could not be identified and data were only available from three of six WHO regions. Researchers considered the number of outbreaks caused by each food and not the amount of ill people in each one.

A total of 236 E. Coli outbreaks that involved haemolytic uremic syndrome (HUS) cases were reported and nearly all in the Americas. Almost 30 percent of all reported outbreaks were associated with either HUS or deaths. Most of the 45 outbreaks with fatalities were also recorded in the Americas region. HUS is a type of kidney failure that can result in lifelong, serious health problems and death.

Significantly more information was available for STEC O157 than for other STEC serogroups.

Regional variation
In the European and American sub-regions of the WHO, the primary sources of outbreaks were beef and produce. However, produce and dairy were the top causes in the WHO Western Pacific sub-region.

“Possible explanations for regional variability include differences in the proportion of specific foods in the diet and how they are prepared for consumption, the level of STEC contamination of foods and live animals from which foods are derived, the virulence characteristics of regionally predominant STEC strains, or differences in how outbreaks are detected, investigated and reported,” according to the report.

Beef and produce were responsible for the highest proportion of cases in the American sub-regions, with source attribution estimates of 40 percent for beef, 35 percent for produce and 12 percent for dairy.

In the European region, ranking of the sources of cases was similar, with an overall attribution proportion of 31 percent for beef; 30 percent for produce and 16.4 percent for dairy.

In Western Pacific sub-region, the most common source was produce at 43 percent, followed by dairy with 27 percent and with game and beef third and fourth at 9 and 8 percent respectively.

Analysis of the data from case-control studies of sporadic infection showed the most important source of STEC globally was beef. In the Western Pacific region chicken was the most significant risk factor.

The report, part of the microbiological risk assessment series, follows another document published last year covering the burden, source attribution, hazard characterization and monitoring of STEC.

It proposed criteria for categorizing potential risk of severity of illness associated with STEC in food, presented initial results on source attribution of foodborne STEC and provided a review of monitoring programs and methodology for the pathogen.

The Codex Alimentarius Commission decided this year at its annual meeting to start developing guidelines to control STEC in beef, leafy greens, raw milk and cheese produced from it, and sprouts.

Irish E. coli report
Earlier this year, the Food Safety Authority of Ireland (FSAI) published advice on STEC detection in food.

Since 2008 – and except for 2011, when Germany had the highest rate due to a large E. coli O104:H4 outbreak – Ireland has had the highest reported STEC notification rate in Europe.

From 2012 to 2016, there were 3,531 STEC notifications in Ireland. Of these, 2,910 were symptomatic and 582 were asymptomatic. Among symptomatic cases, 1 in 20 developed HUS. Of symptomatic cases, 40.3 percent were hospitalized. From 2004 to 2016, five deaths were attributed to STEC and two were fatal HUS cases.

Garvey et al. (2016) reviewed Irish STEC outbreak data from 2004 to 2012 including 219 outbreaks. Food was reported as a suspected transmission route for 21 of them. No microbiological or analytical epidemiological evidence was reported implicating specific foods in any of the outbreaks. Suspect foods were reported in four household outbreaks, minced beef for two and goat and lamb meat for one each.

The report helped to establish the risk in Ireland associated with the consumption of foods in which STEC has been detected.

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