Misleading News - Deli Meat as the Leading Agent for Listeria Infection

A recent news article "Study finds deli meat is connected to more than 90 percent of U.S. listeria cases" states that "90 percent of listeriosis cases in the U.S. come from deli meat, followed by ready-to-eat (RTE) salads at just less than 5 percent."  This article was based on a recently published research publication, "Quantitative risk assessment model to investigate the public health impact of varying Listeria monocytogenes allowable levels in different food commodities: A retrospective analysis". (,International Journal of Food Microbiology, 2022).

What is not clear in this new article is that the research that serves as the basis looks at 30 years of data using metanalysis.  Has control of Listeria improved dramatically in the last 30 years?  Absolutely.  Even the research publication mentions this.  Yes, deli meats are a risk, but there have been far less cases over the past decade with the last notable case in 2020 .  But there are items like salads and cheese that stand out.  

Doing a metanalysis over the past 30 years does not take into account the factor of time and improvement that has occurred in that period.  Secondly, the technology for identification (WGS) and tracking has improved dramatically. 

Looking that the CDC website for the listed outbreaks over the past decade:

2022

Brie and Camembert Cheese – Listeriosis

Ice Cream – Listeriosis

2021

Dole Packaged Salads – Listeriosis

Fresh Express Packaged Salads – Listeriosis

Fully Cooked Chicken – Listeriosis

Queso Fresco – Listeriosis

2020

Deli Meats – Listeriosis

Enoki Mushrooms – Listeriosis

2019

Hard-boiled Eggs – Listeriosis

Not Identified - Listeria monocytogenes Infections

Deli-Sliced Meats and Cheeses – Listeriosis

2018

Pork Products – Listeriosis

Deli Ham – Listeriosis

2017

Vulto Creamery Soft Raw Milk Cheese – Listeriosis

2016

Frozen Vegetables – Listeriosis

Raw Milk – Listeriosis

Packaged Salads – Listeriosis

2015

Soft Cheeses – Listeriosis

Ice Cream – Listeriosis

2014

Commercially Produced, Prepackaged Caramel Apples – Listeriosis

Bean Sprouts – Listeriosis

Cheese – Listeriosis

Dairy Products – Listeriosis

2013

Cheese – Listeriosis

2012

Ricotta Salata Cheese – Listeriosis

2011

Cantaloupes – Listeriosis

International Journal of Food Microbiology

Volume 383, 16 December 2022, 109932

Quantitative risk assessment model to investigate the public health impact of varying Listeria monocytogenes allowable levels in different food commodities: A retrospective analysis

Abstract

Invasive listeriosis is a potentially fatal foodborne disease that according to this study may affect up to 32.9 % of the US population considered as increased risk and including people with underlying conditions and co-morbidities. Listeria monocytogenes has been scrutinized in research and surveillance programs worldwide in Ready-to-Eat (RTE) food commodities (RTE salads, deli meats, soft/semi-soft cheese, seafood) and frozen vegetables in the last 30 years with an estimated overall prevalence of 1.4–9.9 % worldwide (WD) and 0.5–3.8 % in the United States (US). Current L. monocytogenes control efforts have led to a prevalence reduction in the last 5 years of 4.9–62.9 % (WD) and 12.4–92.7 % (US). A quantitative risk assessment model was developed, estimating the probability of infection in the US susceptible population to be 10–10,000× higher than general population and the total number of estimated cases in the US was 1044 and 2089 cases by using the FAO/WHO and Pouillot dose-response models. Most cases were attributed to deli meats (>90 % of cases) followed by RTE salads (3.9–4.5 %), soft and semi-soft cheese and RTE seafood (0.5–1.0 %) and frozen vegetables (0.2–0.3 %). Cases attributed to the increased risk population corresponded to 96.6–98.0 % of the total cases with the highly susceptible population responsible for 46.9–80.1 % of the cases. Removing product lots with a concentration higher than 1 CFU/g reduced the prevalence of contamination by 15.7–88.3 % and number of cases by 55.9–100 %. Introducing lot-by-lot testing and defining allowable quantitative regulatory limits for low-risk RTE commodities may reduce the public health impact of L. monocytogenes and improve the availability of enumeration data.