Coronavirus is able to travel more than 26 feet (eight metres) in cold environments with moving air, according to a study that recreated an outbreak in a food factory.
Researchers at the Helmholtz Centre for Infection Research focused on an outbreak of Covid-19 at a slaughterhouse in Rheda-Wiedenbrueck, Germany, that infected 1,500 workers.
They found a single person in the plant appeared to have infected several others within a 26 feet radius, made possible because of the cold conditions and the constantly circulating air inside the plant.
Similar conditions at plants across the world have led to them becoming epicentres of the virus, and at least five outbreaks have been recorded in the UK.
The study adds to concerns that factories and warehouses’ chilled, ventilated and dark environments are the ideal conditions for the virus to spread.
And it may also suggest the virus could be more of a problem in winter, when more people spend time indoors, close together in colder environments.
Scientists say that viruses survive longer when they’re not exposed to sunlight, that people’s airways are more susceptible to infection when they’re cold, and that the virus can float in the air to infect people far away from an infected patient.
The research found that chilly air circulated without frequent changes, coupled with strenuous work conditions, helped virus particles move large distances.
Their recreation worked out that the transmission of the virus in the German factory took place in a meat cutting area, where the air was cooled to 10°C (50°F).
Professor Adam Grundhoff, one of the study authors and a virologist at the Leibniz Institute for Experimental Virology, said: ‘Our results indicate that the conditions of the cutting operation – the low temperature, a low fresh air supply and constant air circulation through the air conditioning in the hall, together with strenuous physical work – the aerosol transmission of SARS- CoV-2 particles over larger supported distances.’
Professor Grundhoff told Bloomberg: ‘It is very likely that these factors generally play a crucial role in the global outbreaks in meat or fish processing plants.’
Covid-19 outbreaks have been reported at at least five sites across England and Wales.
A plant in Merthyr Tydfil saw at least 34 people testing positive at the Kepak plant in June.
It comes after the whole island of Anglesey, home to 70,000 people, came under the threat of lockdown when a chicken factory shut down because 158 staff tested positive for Covid-19.
Another outbreak at a food plant in Wrexham saw at least 70 people test positive.
The plant process food for Rowan Foods that supplies the likes of Sainsbury’s, Asda, Tesco, Waitrose, Morrisons, Aldi and Greggs from sites around the country.
Mobile testing tents were set up outside Kober Ltd near Cleckheaton, West Yorkshire, which supplies supermarket giant Asda with bacon rashers and joints, after nearly 100 workers fell ill.
Dr Simon Clarke, a cellular microbiologist at the University of Reading, told MailOnline last month that it was notable that food factories seemed to have been the centre of outbreaks more than other factories where people might be close together.
He said: ‘There are problems in this country, in Germany, in the United States. There is something common between them – it’s not happening in engineering or clothing factories where you also might expect people to be in close proximity to one another.
‘One assumes – but it’s just an idea – that the cold environment makes people more susceptible to the virus.
‘Cold weather irritates the airways and the cells become more susceptible to viral infection.’
Meat plants from the US, UK, Europe and South America have seen a rapid spread of coronavirus and some have been forced to shut down.
Dozens of workers have died as a result and activists have said that a lack of social distancing could carry on putting people at risk.
Outbreaks at US meat plants forced them to close earlier this year and led to meat shortages across the country.
And China has continued to test its imported cold food for coronavirus even though science experts claim that transmission through food is extremely unlikely.
Melanie Brinkmann, professor at the Technical University of Braunschweig and Research Group Leader at the HZI, said: ‘Our study sheds light on SARS- CoV-2 infections in a work area in which various factors meet that allow transmission over relatively long distances.
‘The important question now is under what conditions transmission events over longer distances are possible in other areas of life.’
Roughly half of the workers at meat plants in the US are immigrants, according to the Center for Economic and Policy Research and they come from fairly low-income families.
And minority workers at the US plants have been hit the hardest by the outbreaks.
Data from May found that of the coronavirus cases that recorded race and ethnicity, 87 per cent involved minority workers.
The Toennies plant, Germany’s largest pork abattoir, reopened last week after closing for a month.
It has also rolled out new measures to prevent future outbreaks including testing employees twice a week, hiring workers directly and examining ventilation.
The report found that not one Toennies factory in the world was built for a pandemic like coronavirus and the company has invested in air filters.