Hunt is on to trace 300 workers from food factory that supplies Sainsbury's and Asda after 166 staff tested positive for Covid-19

Public health bosses are desperately trying to track down 300 workers after 166 colleagues tested positive for Covid-19 at a food processi...

Public health bosses are desperately trying to track down 300 workers after 166 colleagues tested positive for Covid-19 at a food processing site that supplies Sainsbury's and Asda.

More than 1,000 people work at Rowan Foods in Wrexham, which has seen an outbreak of coronavirus among staff, more than three months after a walkout over concerns there was a lack of protection for workers.  

In a statement today, Public Health Wales said: 'We are working with Betsi Cadwaladr University Health Board to urgently contact just over 300 workers that have not yet presented for testing.

Workers at Rowan Foods in Wrexham protested over a lack of proper protection amid the coronavirus lockdown in April. Now an outbreak has seen 166 workers diagnosed with Covid-19

Nearly a third of Rowan Foods 1,000 staff have not been tested for Covid-19 after an outbreak

'As we would expect with any focused track and trace process, we will identify additional asymptomatic cases. Finding these cases does not mean that the rate of infection in the Wrexham area is increasing as a whole.

'There is no evidence that Rowan Foods is the source of the outbreak.

The multi-agency team managing the outbreak with Public Health Wales will continue to review the situation and work with the employer, their workforce and wider community to bring this outbreak to a swift conclusion.'

The Wrexham site first hit the headlines in relation to coronavirus earlier this year, when workers walked out in April in an apparent protest over what they felt was a lack of protection from the virus.

Unite claimed the company did not deal with health and safety concerns urgently, after negotiations over sick pay broke down.

Rowan Foods told the BBC:  'We have been proactively introducing new operational changes at the site for some months now, since the issuing of government guidance for the food industry in March 2020, to ensure that we maintain social distancing wherever practically possible, and have also included new mitigations such as screens and visors.'

The firm supplies major supermarkets including Sainsbury's and Asda. 

The Rowan Foods outbreak and the cluster of cases around the Anglesey 2 Sisters abattoir have so far accounted for more than 300 infections.

There have been claims that the island of Anglesey, home to 70,000 people, could be placed under lockdown to contain the outbreak at the 2 Sisters chicken factory.

Another 34 cases were reported at Kepak in Merthyr Tydfil.

Last Wednesday tinned food giant Princes was forced to close its Cambridgeshire factory for 24 hours following an outbreak of coronavirus among staff. 

Staff from the Wisbech plant began displaying coronavirus symptoms and were instructed to self-isolate and contact health authorities to get tested. 

Fourteen of the factory's 407 employees tested positive, forcing the plant to close on Tuesday while deep cleaning was carried out. 

A company spokesperson said the 14 infected employees would be 'logged as part of track and trace efforts'.  

Number 10's chief scientist Sir Patrick Vallance said food safety officials ruled the risk of catching coronavirus from eating meat was slim

Number 10's chief scientific adviser Sir Patrick Vallance said food safety officials who looked 'carefully' at whether meat is a vector ruled the risk was slim.

Dismissing fears of contaminated meat in Thursday's Downing Street press conference, he said: 'The meat itself is not the issue but the environment in which this takes place is.'

Sir Patrick added that the virus 'prefers' cold places such as meat-processing plants, which are often chilled to preserve them.

He added it can be 'difficult' to keep workers separated in cramped factories and communal areas, and warned staff may have to speak loudly — which studies have suggested can spread the virus. 

England's chief medical officer Professor Chris Whitty said: 'Meat-packing factories, abattoirs and food-processing and packing areas have led to several outbreaks around the world and, therefore, are an area where we'll have to take the mitigation efforts particularly seriously.'

ARE MEAT AND FOOD FACTORIES HOTSPOTS FOR THE CORONAVIRUS? 

As news has emerged of food factories around the world experiencing outbreaks of Covid-19, experts have suggested conditions inside the plants may be conducive to the spread of the virus. 

Dr Simon Clarke, a cellular microbiologist at the University of Reading, told MailOnline 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.' 

Dr Chris Smith, a virologist at the University of Cambridge, said on LBC 'temperature is going to play a part'.

He explained: 'When I'm breathing I'm blowing out droplets of moisture from my respiratory tract and the virus which is growing in there would be packaged up in the droplets. 

'Now the droplets will hover for a period of time in the air and then sink to the ground... and if it's very dry, cold air - and cold air carries less moisture, remember - the droplets will stay smaller and stay airborne for longer. 

'If it's very humid, moisture joins them, makes them bigger and heavier, and they fall and they drop out of circulation faster - so temperature could be a factor.'

Sunlight is also known to degrade viruses and make them less able to survive on surfaces that are exposed to UV light.

Rays of sunlight are thought to damage the genetic material inside the virus, making it less able to reproduce and killing it faster. 

Professor Calum Semple, a disease outbreak expert at the University of Liverpool, told The Telegraph that cold, sunless food factories are ideal conditions.

He said: 'If I wanted to preserve a virus I would put it in a cold, dark environment or a cool environment that doesn't have any ultraviolet light - essentially a fridge or a meat processing facility...

'The perfect place to keep a virus alive for a long time is a cold place without sunlight.' 

But the temperature alone does not appear to be a controlling factor in coronavirus outbreaks. 

Dr Michael Head, a global health researcher at the University of Southampton, said he thought close proximity was most likely to be behind the factory outbreaks.

He said: 'Whilst refrigeration may be a contributory factor to the spread of the virus, the key factors are likely to be the number of people close together in indoor conditions. 

'Some of these factories have onsite 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.

'Levels of adherence to measures such as washing hands is uncertain and there is unlikely to be widespread use of PPE.'