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Rising Incidence of Listeriosis in EU Leads to New Research

Updated: Nov 22, 2018


Rising Incidence of Listeriosis in EU Leads to New Research

The European Union (EU) has always had a different and more tolerant attitude toward Listeria monocytogenes (Lm) than the U.S. Given that in many ways the EU was typically more aggressive on food safety than the U.S., this was always an odd difference between the two regulatory approaches. But now, with this new report, the EU may be starting to wonder if it needs to get a little more aggressive with Lm.  


Although the European Union has increased its application of food safety criteria for Listeria monocytogenes (Lm) in ready-to-eat (RTE) foods since 2006, it is now seeing a statistically significant increasing trend of human listeriosis between 2009–2013. Because of this, the European Food Safety Authority (EFSA) conducted and delivered a Scientific Opinion on Lm contamination of RTE foods and the risk for human health in the EU. The purpose was to summarize and evaluate the most recent information on Lm in RTE foods along with the factors related to contamination in the food chain and consumption patterns that may contribute to the trend.


Research was based, in part, on a 2010–2011 EU-wide baseline survey (BLS) which estimated the prevalence and concentration of Lm in three RTE foods at retail: packaged (not frozen) smoked or gravad fish, packaged heat-treated meat products, and soft or semi-soft cheese.

The proportion of samples with Lm counts exceeding 100 colony forming units (CFUs) per gram at the end of shelf life was 1.7% for RTE fish, 0.43% for RTE meat and 0.06% for RTE cheese.


Following are key facts and recommendations from the draft scientific option, on which the EFSA is requesting comment:

  • About 2,200 confirmed human listeriosis cases were reported in the European Union and European Economic Area (EU/EEA) in 2015, with an increasing trend in females over 25 years and males ≥75 age in 2008–2015.

  • The highest incidence rate was seen in the ≥75 age group in 2015, with 2.20 and 1.30 cases per month per million persons for males and females respectively.

  • Most listeriosis cases appeared to be linked to food contaminated with medium to high (3.5 – 7.5 log10 CFU/serving) Lm concentrations.

  • In 2015, the listeriosis incidence rate was higher for males than for females over 45, but for those aged 15-44, the rate was higher for females. This is believed to largely reflect pregnancy-related listeriosis.

  • The incidence rate of confirmed human listeriosis in females significantly increased for the 25-44 and ≥75 age groups with a monthly increase estimated at 0.64% and 0.70%. For males, the incidence rate increased significantly for the ≥75 age group only (0.50%).

  • Foods associated with the largest number of cases per year were cooked meat (863 cases), sausage (541), gravad fish (370), cold-smoked fish (358), pâté (158), soft and semi-soft cheese (19) and hot-smoked fish (7).

The research suggested that the increasing trend in cases was likely due to both the increased population size of the elderly and the increased proportion of susceptible persons over 45 years old. However, this does not explain the increase in the 25-44 year old females; additionally, the paper noted that despite the increase, fewer than 2,300 cases per year were reported in the EU/EEA. Additionally, most listeriosis cases appear to be sporadic, and reported outbreaks are commonly small, making it difficult to detect links between human cases and causative foods.


However, the major source of RTE food contamination is considered to be persistence of Lm in food processing environments, caused by both improper hygiene conditions and the highly adaptive capacity of Lm against physical–chemical factors (e.g., biofilm-forming capacity).  While the RTE food categories typically associated with human listeriosis (meat and meat products, fish and fish products, and milk and milk products) continue to have a significant public health impact, other foods have been implicated in outbreaks (e.g., cantaloupe, caramel apples, ice cream) illustrating that almost all RTE foods may support growth under certain circumstances and/or that when consumed by highly susceptible people, have the potential to contribute to disease.


During the period 2008–2015, reported annual non-compliance of Lm in RTE foods at processing sites was highest in fishery products (3–10%) and meat products other than fermented sausage (1–7%). Non-compliance in the remaining RTE food subcategories was 2% or less.


The lower level of annual non-compliance at retail (below 1% for most years) than at processing is at least partly explained by the application of the different limits of food safety criteria at retail and processing.


Because unsafe practices (including storage time and temperatures) are not uncommon for the elderly (>10% of persons studied), this may impact their risk. However, there is a wide variation within this broadly defined group, thus it is problematic to generalize about their food handling behaviors and impact. Additionally, differences between country cultures, socioeconomic factors, traditions and types of food may have an impact, as well as the highly variable temperature ranges of domestic refrigerators. From the study, the EFSA panel made the following recommendations:

  • Awareness should be raised among all stakeholders in the food chain about the potentially increasing problem of Lm in RTE foods since the proportion of European citizens in high-risk groups is expected to increase.

  • There is a need for data to evaluate changes over time in the consumption of RTE foods and other food categories.

  • Improvements to the information for risk assessment and risk management are recommended (e.g., by collecting comparable data on human listeriosis cases that are more aligned with the concepts of risk groups in terms of the number of cases, their consumption habits, and socioeconomic–demographic data).

  • Better information should be obtained on how the dietary practices and food handling among elderly groups are affected by ageing, and how this may be linked to an increased exposure to Lm.

So, my take on this is that EFSA has essentially acknowledged that Lm levels are increasing but are “blaming” this on consumer behavior. That may be an over simplification but that is my basic take from this report. There is no mention of looking at how Lm is regulated and certainly the EU is not approaching Lm regulation with the same intensity as the U.S. FDA. Hard to know who has the right approach – the reported number of cases of Lm in the EU is about the same as in the U.S. (approximately 2,500 cases per year) with fewer people living in the U.S. (324 million in the U.S. compared with 509 million in the EU). So, who has the best regulatory strategy for controlling Lm? I think this would make for an interesting debate!

You can submit comments or view more information from EFSA on the Consultation page.

About The Acheson Group (TAG)

Led by Former FDA Associate Commissioner for Foods Dr. David Acheson, TAG is a food safety consulting group that provides guidance and expertise worldwide for companies throughout the food supply chain. With in-depth industry knowledge combined with real-world experience, TAG's team of food safety experts help companies more effectively mitigate risk, improve operational efficiencies, and ensure regulatory and standards compliance. www.AchesonGroup.com

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