Otherindependent cross-checkabstract checked★ key study I-VEG-132 standard review

Leafy greens: frequent but rarely deadly outbreak source

Outbreaks attributed to fresh leafy vegetables, United States, 1973-2012.

Overview

Herman KM et al.. Epidemiol Infect 2015 · PMID 25697407 · DOI 10.1017/S0950268815000047

Over 40 years, US leafy-vegetable outbreaks caused 20,003 illnesses and 19 deaths; many involved infected food workers.

Does the study support the specific claim? Yes · Methodological quality: moderate

Study explained simply

What did the researchers want to find out?: Describe US leafy-vegetable outbreaks.
How was the study done?: Surveillance review.
How many people, animals or samples were studied?: 606 outbreaks.
What was actually found?: Large outbreaks, mostly norovirus, low fatality.
How large was the observed effect?: CFR ~0.1%.
What do the results mean in everyday life?: Washing hands and safe handling matter as much as farming.
What are the study's limitations?: Outbreak data only.
What does it say about Elawady's specific claim?: Supports the claim with context.
Do the results apply to Germany and Europe?: US.
What can explicitly not be concluded from this study?: Cannot estimate risk per serving.

Authors: Herman KM et al.
Journal: Epidemiol Infect
Year: 2015
Identifier: PMID 25697407 DOI 10.1017/S0950268815000047
Verification: verified – PubMed efetch 2026-10-26; Crossref 2026-10-26
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: Funding (PubMed grant list): Intramural CDC HHS

What are the characteristics of US outbreaks attributed to leafy vegetables?

Study design: Other – Review of national outbreak surveillance data (CDC FDOSS)
Population: US outbreaks reported to CDC
Country: USA
Period: 1973-2012
Sample size: 606 outbreaks; 20,003 illnesses
Inclusion and exclusion criteria: not stated in abstract

Exposure / intervention: Leafy vegetables as outbreak vehicle
Comparator: Other food types
Endpoints: Outbreaks, illnesses, hospitalisations, deaths; pathogens; settings
Statistical methods: Descriptive

Results: 606 leafy-vegetable outbreaks, 20,003 illnesses, 1,030 hospitalisations, 19 deaths; outbreaks larger on average than other food types; norovirus 55%, STEC 18%, Salmonella 11% of confirmed aetiologies; 85% from restaurant/catering food; ill food worker implicated in 31%.
Absolute risks: not reported
Authors' conclusion: Control efforts should span from harvest to preparation.

Case fatality 0.095%; hospitalisation 5.1% (stats/C-VEG-03_outbreaks.py).

Supports that leafy greens are prominent outbreak vehicles, while showing low fatality and a large role of food handling.

Painter 2013: poultry caused most deaths.

US data; EFSA 2013 similar for EU.

Supports the claim with important context.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	moderate
Risk of bias	some concerns
Precision of results	moderate
Directness	direct
Reproducibility	replicated
Consistency with the overall evidence	consistent
Regional transferability	moderate
Adequacy of the interpretation (by the archive)	not applicable

Per-serving risk.