Hundreds of workers have tested positive for coronavirus at meat processing plants and abattoirs.

They include a chicken processing site in Anglesey, where more than 150 workers have become infected with Covid-19, and plants in Wrexham and West Yorkshire.

There have also been major outbreaks in Germany, France, Spain and the US.

Bev Clarkson from the union Unite, says: "Unite has warned time and again that coronavirus outbreaks at meat processing factories throughout the UK were likely".

Why are meat workers getting coronavirus?

People get infected with coronavirus from droplets, which may be coughed, sneezed or exhaled by an infected person.

The infection may come through close contact with the person or by touching infected surfaces.

"Factories and, in particular, indoor areas which are cold and damp, are perfect environments for coronavirus to linger and spread," according to Lawrence Young, Professor of Molecular Oncology at the University of Warwick.

"Virus-containing droplets from infected individuals are more likely to spread, settle and stay viable."

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Another possible factor in these refrigerated workplaces is noisy machinery, which requires people to talk more loudly or shout, which can increase the spread of infected droplets

What about working conditions?

It is difficult to keep workers two metres apart when they are working on fast-moving production lines, and the absence of daylight may also help the virus to survive.

"When you have people standing right next to each other working heavily - because of course this is a difficult job - and breathing heavily, you have a chance for spreading virus from just one infected individual to many that are in close proximity," said Tara Smith, professor of epidemiology at Kent State University in Ohio.

"And then of course you have a chain of dominoes after that."

There is no evidence that the meat products themselves could be a source of Covid-19 infection at the plants.

The Food Standards Agency said it was very unlikely that you could catch coronavirus from food because that is not how it is known to be transmitted.

It's not just conditions inside the plant that may be increasing the risk of coronavirus.

"Some of these factories have on-site or nearby accommodation where there are several people in each dormitory. They may be transported on a bus to the site of work, and they will be indoors together all day," said Michael Head, senior research fellow in global health at the University of Southampton.

The Unite union says that while it represents many workers in the meat processing sector, plants often employ migrant workers who may not be entitled to full sick pay, so could lose money if they self-isolate after getting sick.

The union says they often do not speak English as a first language and are worried about losing their jobs, so may be reluctant to raise concerns.

The British Meat Processors Association (BMPA) told Reality Check that most workers in its members' plants are full employees rather than agency staff.

What is being done to protect workers?

The government has issued guidelines on working safely in food manufacturing - including keeping workers at least two metres apart when possible.

The BMPA has also issued guidance, including cleaning factories more often than usual, isolating staff who develop symptoms and staggering start times and break times.

It also suggests providing additional personal protective equipment (PPE) such as visors, if available - staff in meat processing facilities usually wear PPE, but that does not necessarily include masks.

Dr Yvonne Doyle, medical director at Public Health England, said the organisation had been advising on a number of outbreaks in factories, some of which involved meat processing.

"Where outbreaks occur, we are working closely with NHS Test and Trace to ensure appropriate testing and tracing of contacts, both within and outside of the workplace. Where required, mobile testing units are being deployed to ensure large workforces are tested promptly."

In Germany, the government is banning the outsourcing of abattoir staff - workers will have to be employed directly by the company.

A source close to Defra in the UK told the BBC that another of the factors being looked at in Germany is the poor training and poor language skills of the mainly Eastern European workforce in the meat processing industry, which was preventing the rules being followed