Aerosols in meat plants as possible cause of Covid-19 spread.

Between March and June 2020, a series of outbreaks of coronavirus (SARS-CoV-2) occurred in meat factories extending from Europe to North America, including those in the USA, Canada, Germany, France, Spain and the UK.

Many hundreds of workers were affected in an outbreak at Sioux Falls, South Dakota, USA, and at Tonnies, near Gütersloh, North Rhine-Westphalia, Germany, as well as near High River, Alberta, Canada. In a meat factory in Anglesey, Wales, more than 150 workers were affected.

Various reasons have been proposed for the outbreaks, including the crowded working conditions, the cold working environment, workers not wearing masks properly or not at all, and the need for workers to talk loudly over the background noise of machinery. Most experts and commentators seem to be baffled and have spoken about the need for further investigations.

While those factors may have been involved there are certain practices within such facilities which, I believe, should also be considered. Common to meat factories is the frequent washing down and brushing of floors and surfaces to maintain hygiene. Those procedures are very effective methods for generating large quantities of droplets and aerosols, especially when high-pressure hosing is employed.1 If the floor or surface is contaminated with coronavirus, perhaps unknowingly, by droplets from one or more infected workers, it is likely that aerosols of infectious particles will be dispersed into the atmosphere and would then pose a considerable risk of airborne virus infection for the workers in that environment. Within a chilled atmosphere workers could be at risk for relatively long periods as the virus will be more stable.

The occurrence of a high incidence of infection in meat factories within a short period is, I believe, more likely to be the result of workers being infected from the same source simultaneously rather than by person-to-person transmission. In the latter case, the occurrence of cases would have been more protracted due to the five- to 14-day incubation period, instead of the sharp ‘spikes’ that were seen. This is not to say, of course, that both mechanisms did not occur. There might have been a series of introductions, followed by infection from the contaminated environment, followed by person-to-person transmission.

If this hypothesis is correct then there is a need to provide better protection from airborne virus for workers within meat factories. Steps in that direction should first include the cessation of procedures that are likely to produce aerosols. This could be done by sluicing down with water and using rubber squeegees instead of brushes and hoses. Pressure hoses could be replaced by steam hoses and workers could be better protected with virus-protective masks, ie, those of FFP2/3 standard or better.

There is a need to provide better protection from airborne virus for workers within meat factories

Finally, workers could be screened frequently to reduce the likelihood of those with coronavirus entering the facilities.