What explains the high rate of SARS-CoV-2 transmission in meat and poultry facilities?

June 4, 2020

Quentin Durand-Moreau [1]
Anil Adisesh [2]
Graham Mackenzie [3]
Jonathan Bowley [4]
Sebastian Straube [1]
Xin Hui Chan [5]
Nathan Zelyas [6]
Trisha Greenhalgh [7]

[1] Division of Preventive Medicine, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
[2] Division of Occupational Medicine, Department of Medicine, University of Toronto and St. Michael’s Hospital, Toronto, Canada
[3] GP Specialty Trainee, NHS Education for Scotland, UK
[4] Medical student, University of Nottingham, UK
[5] Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, UK
[6] Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada
[7] Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK

Series editor: Trish Greenhalgh

On behalf of the Oxford COVID-19 Evidence Service Team
Centre for Evidence-Based Medicine, Nuffield Department of Primary Care Health Sciences
University of Oxford

Correspondence to Quentin Durand-Moreau  durandmo@ualberta.ca


 

Question: What explains the high rate of Sars-CoV-2 transmission in meat and poultry facilities?

Brief answer:

  1. The working environment in these facilities is favourable to SARS-CoV-2 persistence (metallic surfaces, low temperatures and relative humidity).
  2. The working environment may help SARS-CoV-2 transmission (crowded working places, shared transportation, production of aerosols, droplets, fomites).
  3. A vulnerable, low-paid workforce may be under pressure to keep working despite having symptoms of COVID-19.

 An extended abstract is below; a full paper has been submitted for publication and will be linked from this page when published as a preprint.

Background
Numerous coronavirus disease 2019 (COVID-19) outbreaks have been described in relation to meat and poultry processing facilities in different countries. The subject is attracting considerable interest from the mainstream media and on social media.

We wanted to better understand why there are clusters of COVID-19 in these facilities. Our review questions are listed below.

  1. How is the issue being framed in the lay press and social media?
  2. What is the nature of the work process in meat and poultry facilities?
  3. How does the working environment affect persistence and transmission of SARS-CoV-2 in meat and poultry facilities?
  4. How conducive are meat and poultry facilities to airborne viruses?

Methods
The study was undertaken in May 2020. We followed two parallel research approaches: First, an analysis of lay media press articles using a Google News search, and posts on Twitter using an analytic approach described separately. We charted key themes from identified articles until saturation was reached (i.e. until new press articles did not contain any new themes). Second, a rapid keyword search of PubMed and Medline databases. Relevant papers suggested by co-authors with specialist expertise were also included. All study types were included. The data were drawn together iteratively using narrative synthesis, progressively building an understanding of the multiple interacting factors at human, material, organisational and system level.

Results

Q1.  How is the issue being framed in the lay press?

Recent newspaper articles depict an industry dominated by large multinational companies, working to “just-in-time” supply chain pressures and oriented to maximising efficiency. The workforce is depicted as extremely vulnerable and the nature of the work as making it difficult or impossible to implement and follow high standards of infection control. Some plants appear to have seen extremely high levels of transmission. Poor-quality and at times overcrowded communal living and travelling conditions are depicted as exacerbating the risks. The tension between regulatory controls (which often require prolonged closures) and lobbying by powerful industry voices (which push for remaining open) plays out differently in different countries.

Q2.  What is the nature of the work process in meat and poultry facilities?

Meat slaughtering and processing involves various steps undertaken in crowded, intensive production-line conditions and involving both low and high temperatures, in working environments with high levels of relative humidity and requiring (but perhaps not actually having) efficient ventilation systems. Working environments are typically noisy.

Q3. What is the impact of aspects of the working environment on the persistence of SARS-CoV-2? 

SARS-CoV-2 survives longer in lower temperatures and both high and low relative humidity. Personal protective equipment (PPE) properly worn and removed is likely to reduce transmission of the virus in this environment. However, there may be barriers to the proper and consistent wearing of such equipment, even when it is provided, and workers may not be trained or adequately supervised. The need for raised voices to overcome noise may increase transmission of SARS-CoV-2 through aerosolisation.

Q4.  Can viruses be airborne in meat and poultry factories?

Whilst transmission from animal carcases is unlikely, there is some evidence that food handlers may be the primary sources of indoor bioaerosols in the food industry. Employees may carry and distribute micro-organisms through their clothes, by contact, coughing or sneezing. Poor ventilation systems may play a significant role as well as improper maintenance and sanitation. There is no direct evidence that SARS-CoV-2 is transmitted from human to human by airborne spread in this environment. 

Conclusion
Multiple interacting factors explain the high rate of infection and the occurrence of clusters in meat and poultry plants. A recent CDC report on meat and poultry facilities and Covid-19 [1] included a summary table of key occupational health issues and recommendations, which we reproduce with permission below, acknowledging the work of lead author Jonathan Dyal.

Table 1: Observed challenges and recommended changes in practice in response to COVID-19 among workers in meat and poultry processing facilities – selected states, April 2020 – reproduced under creative commons licence with acknowledgement to Jonathan Dyal and US Centers for Disease Control and Prevention [1]

References

  1. Dyal JW, Grant MP, Broadwater K, et al. COVID-19 Among Workers in Meat and Poultry Processing Facilities ― 19 States, April 2020. MMWR Morb Mortal Wkly Rep 2020;69:557–561. DOI: http://dx.doi.org/10.15585/mmwr.mm6918e3external icon.