If there is a paradise for SARS-CoV-2, it would probably be a slaughterhouse. Work units in meat plants are cooled to under 12 degrees Celsius. Workers stand near one another and sweat as they labor under pressure - an ideal situation for viruses transmitted by droplets, aerosols or contact.
Canadian and British researchers working under Quentin Durand-Moreau of the University of Alberta have studied the working conditions in meat plants. The "metallic surfaces” and the "low temperatures,” they report, enhance the longevity of viruses like SARS-CoV-2. They also explain that the plants are often very loud: "The need for raised voices to overcome noise may increase transmission of SARS-CoV-2,” the researchers wrote. Workers, they argue, also feel pressured by their precarious work situation to "keep working despite having symptoms of COVID-19.”
"The working conditions in the slaughterhouses cannot be reconciled with the hygiene measures that are currently necessary,” warns Isabella Eckerle, the head of Geneva Center for Emerging Viral Diseases. At the Tönnies slaughterhouse, the virologist says, the large number of infected employees points to "an undetected superspreading event.” She explains that, if there was close contact and unfavorable working and living conditions, a single infected person or a small number of infected people could potentially have infected many other employees.
"The physical exertion during the work, which leads to greater virus expulsion, is another possible factor,” Eckerle says. Damp hands and gloves, aprons and clothing worn during meat handling could also facilitate the virus being transmitted via smear infections.
Coronaviruses have a relatively strong, fatty shell that gives them a kind of rubber-like protection in cool conditions. That makes them robust. Researchers have already shown that SARS-CoV-2 can survive up to 72 hours on surfaces in temperatures between 21 and 23 degrees Celsius (70 and 73 degrees Fahrenheit). Lower temperatures extend that time even further. Experiments show that the viruses can survive longer than 28 days at 4 degrees Celsius.
Coolness is also ideal for the spread of SARS-CoV-2. Health expert Tom Jefferson from Oxford University says the virus transmits best at temperatures between 0 and 10 degrees, with low humidity, high air pressure and little wind. High temperatures and strong UV radiation, he says, inhibit the spread of the virus.
That’s good news for summer in central Europe, where the virus’ infectiousness is presumably decreasing at the moment. But this is not the case in cooled slaughterhouses. To make matters worse, the plants’ cool air is constantly circulated by air conditioning, a constant stream of air that also helps the viruses spread. These can be kept in the air for several hours by fine aerosols and travel large distances.
Even just a few infected workers would be enough to trigger a "local epidemic,” says Jefferson. "If, on top of that, workers also live in shared accommodations and, for example, take the same buses from those accommodations to the abattoirs, it would be very difficult to stop the spread.”
Are Consumers At Risk?
The Tönnies contract workers were thus in constant danger of infecting themselves. But are the consumers who buy and eat the slaughterhouse’s meat also in danger?
Coronaviruses are even more stable when they are frozen than when they are cooled. Experiments with other coronaviruses have shown that they can remain infectious for up to two years at -20 degrees Celsius. Nevertheless, the transmission of SARS-CoV-2 from supermarket meat to a consumer is unlikely.
The German Federal Institute for Risk Assessment (BfR) writes that the contamination of meat or meat products with coronaviruses could "theoretically take place during the slaughter or during the meat cutting and processing.” The BfR writes, however, that so far, there have been "no known infections with SARS-CoV-2 via the consumption of meat products or contact with contaminated meat products.”
Theoretically, coronaviruses could be transmitted from an infected person onto sausage or meat, the BfR continues. But in the current SARS-CoV-2 outbreak, it claims, the mode of transmission through meat consumption "plays no role, based on current knowledge.”
"It is very unlikely that supermarket customers will be infected by meat,” says Jefferson. Of course, normal hygiene rules should be maintained with meat. "Wash your hands often, never consume raw meat, always cook or fry it, and store the meat separately from other foodstuffs,” the researcher advises.
How could outbreaks like the one in Rheda-Wiedenbrück be prevented in the future? Researchers from the United States’ Centers for Disease Control (CDC) have examined COVID-19 cases in 115 slaughterhouses in the U.S. In the pandemic’s early months, about 4,900 of 130,000 workers became infected. By the end of April, this had led to 20 deaths due to the virus.
Like others, the CDC researchers blame the relatively large numbers of cases on the small distances between the workers and the tight living and transport conditions. They have called for the implementation of "outdoor break areas,” "physical barriers between workers,” stricter hygiene measures and additional staff who regularly and thoroughly disinfect the workplaces.
But Jefferson is skeptical that measures like that will go far enough. "I’m not sure how distancing and hygiene rules can even be maintained in such working conditions,” he says. To prevent local outbreaks, he argues, radical steps are necessary – like, for example, comprehensive testing.
And yet even that doesn’t always seem to help. The workers in many slaughterhouses were tested in May, including Tönnies. A number of tests came back positive at the time. But that also didn’t stop a local outbreak.