Coronavirus: in confined spaces, these clusters that cause fear of a second wave

Text by: Romain Philips Follow

The appearance of new foci of contamination, mostly located in closed places, are more and more numerous, making the authorities fear the scenario of a second wave.

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Nearly 1 200 cases and at least one death in a mine in Russia. Twelve  mines closed in Poland after the discovery of several thousand Covid-19 patients among employees of a mining group. Thousands of positive tests among employees of slaughterhouses or meat processing plants in Germany, France, United States, Spain, Netherlands and England… Homes for migrant workers infected with coronavirus in France, Italy or Singapore. A prison in Chicago has a contamination rate 30 times that of the region.

As Europe gradually looses restrictions, America is hit hard by the Covid-19 pandemic and the World Health Organization warned of the pandemic "  far from over  " which "  accelerates  ", the clusters, or centers of contamination, are more and more numerous. And they emerge especially in closed places.

"  What we are now seeing is that many of the clusters that we are discovering are clusters of confined environments  ," explained Arnaud Fontanet, member of the Covid-19 Scientific Council, responsible for advising the French government on the management of the crisis. Before the commission of inquiry of the National Assembly, he notably recalled the possible existence of contamination, not by droplets, but by aerosols, "  particles which are only a few microns in diameter and which remain in suspension in the air  ”.

Faced with this contamination due to the suspension of viral particles in the air, "  we are disarmed  ", alerts the epidemiologist. But it tempers, this mode of transmission "  is not yet proven but becomes more and more plausible  " and "  fortunately, it is not the main mode of transmission  ".

Fear of a second wave

In France for example, while the virus has circulated considerably less since the end of confinement, 272 clusters (82 of which are still under investigation) have been detected since May 9, according to the latest assessment by Santé Publique France . Among these sources of contamination, the majority have been identified in enclosed places such as health or school establishments, businesses, family homes or young workers. In scientific journals, more and more studies also point to closed places as places where the spread of the virus is increased. It would be pushed in particular by the stagnation of the virus in the air when it is not renewed.

The increase in these clusters makes authorities fear the appearance of a second wave of contaminations, thus forcing certain governments to set up local confinements. Since Monday June 29, the city of Leicester, in the United Kingdom is reconfigured because of an outbreak of cases , due to an epidemic in food production factories and to large gatherings around restaurants, according to the Sunday Times . In Germany, one of the two cantons confined since June 22 is no longer so while the second is still confined until July 7 , because of the outbreak declared in the largest slaughterhouse in Europe. This Wednesday, July 1, the northern suburbs of Melbourne have been reconfigured. Earlier, 10 residential areas of Beijing were quarantined in mid-June after the discovery of a cluster on one of the most important agricultural markets in the city, after several tens of days without new cases.

Factors in the spread of the virus are increasing in slaughterhouses

But among these confined places, some are more favorable to the spread of Covid-19. This is particularly the case of slaughterhouses, where thousands of cases have been detected worldwide. "  There are a lot of factors that contribute to the fact that the personnel of these slaughterhouses have been more exposed and have worked in professional environments which are themselves more exposed because they are favorable to the survival of the virus,  " explains Gilles Salvat, director General Delegate for Research at ANSES (National Agency for Food, Environmental and Occupational Health Safety).

In these establishments, and particularly in the cutting workshops, the hypothesis that the working conditions bring together several elements conducive to the spread of Covid-19 is favored. On the other hand, that raising the possibility of contamination by meat is today ruled out.

The ambient temperature in these factories, necessary to refrigerate the meat, varies between 4 and 10 degrees and would favor the survival of the virus, just like the high humidity of these environments. Two elements that allow the virus to spread in the air, but also on work surfaces. “  We have a lot of stainless steel surfaces and we know that it is rather a surface favorable to the survival of the virus. Especially since it is in a cold and humid environment : two factors in the survival of the virus,  ”analyzes Gilles Salvat, a fine expert on the situation in slaughterhouses.

Read: Coronavirus: the meat industry hit by an outbreak of new cases in Europe

Another hypothesis put forward: the difficulty for employees to enforce barrier gestures. If the wearing of gowns, charlottes and masks has been widespread in abattoirs since well before the world pandemic of Covid-19, their effectiveness is questioned. While health rules recommend changing the mask every 4 hours because of the degrading filtering capacities, in an atmosphere such as that of slaughterhouses, this period is shorter. “  When you release air at 37 degrees to a 4 to 10 degree atmosphere, the first thing it does is that the water condenses. So the mask will get wet very quickly and will lose some of its filtering properties when it is used,  ”explains the expert.

These noisy environments, forcing employees to speak louder or lower their masks to be heard also contribute to a stronger expulsion of potentially contaminated droplets and aerosols. An element which would have been aggravated, in the case of the German slaughterhouse, by the ventilation system, according to the results of the investigation of Martin Exner , expert in hygiene and public health at the University of Bonn, disclosed on June 26 . According to his work, the ventilation system would facilitate the movement of the virus in the air of the slaughterhouse.

Added to the overcrowding caused by the large workforce, the fact that work in the animal industry did not stop during confinement and the dilapidated and cramped accommodation conditions of the workers (mainly in the case of the slaughterhouse German ), the elements contributing to a rapid spread of the virus have multiplied.

Physical professions, more vectors of virus transmission?

Physical occupations, more generally, can be conducive to a higher spread of Covid-19. "  If you are in jobs that are extremely physical, the respiratory rate, so the speed at which you are going to expel air is much more important and therefore we can go beyond 1m 50 or 2m and send particles contaminating further  ”notes the CEO of ANSES

A phenomenon that may have played in the mines which have been the source of many contaminations. In addition, in these excavations, the numerous drafts and ventilation can also favor the transport of contaminated aerosols between employees. In the United States, for example, several mining unions denounce an "  inadequate ventilation in underground mines  " while the measures of physical distancing are not applied.

In other words, the safety distance to be respected in order to avoid contaminating a person could be longer in enclosed places where a large number of employees carry out a physical trade. “  To give an idea, when we asked the High Council of Public Health about the distance between athletes, we said that for an athlete who jogs or bikes it is more like 10 meters because his respiratory rate as well as the speed and the distance of projection of the respiratory droplets were increased  ”, concludes Gilles Salvat.

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