The acting Chief Medical Officer Dr Ronan Glynn has expressed concern at the number of outbreaks of Covid-19 in workplace settings.

Speaking at the Department of Health press conference this evening, Dr Glynn said: "We are now seeing outbreaks of the virus in a range of work settings, including in construction, in fast food outlets and in supermarkets.

"We can't underestimate how quickly clusters develop. We have come so far together, but we need to stay vigilant to prevent a resurgence across the whole country in the coming weeks."

His comments come after a building site in Dublin city centre was closed down temporarily after a number of workers tested positive for Covid-19.

Dr Glynn said there had been more than 20 cases associated with the construction site and a number of other workers from the site had been tested and were waiting for results. 

He said this was the first significant cluster on a construction site and there was a full outbreak control team in place, but he wanted to use it to remind employers of their need to ramp up their efforts to put the safety of staff and customers first. 

He said there had been a couple of outbreaks at fast-food outlets, including one in Kildare linked with a significant number of cases. But he said there had not been a case linked to it for a number of days.

He also said there was a number of outbreaks associated with retail settings, but these often involved small numbers of people and many were managed locally. 

"Many workplaces have introduced the new regimes and safety measures necessary to reopen their businesses," said Dr Glynn.

"I would remind all employers that the workplace and most particularly, shops, services and supermarkets, are the new frontline, we are asking you to do everything you can to put the safety of your staff and customers first.

"With the increase in outbreaks in our communities, I would urge everyone to wear face coverings in healthcare settings and when shopping, including in the supermarket and other indoor retail services," added Dr Glynn.

There have been no further deaths reported from Covid-19 in Ireland, while six new cases have been confirmed by the Department of Health.

There have been a total of 1,753 Covid-19 related deaths in Ireland. There are now a total of 25,766 confirmed cases of Covid-19 in the country.

In Northern Ireland, no further coronavirus deaths were recorded for the seventh consecutive day, so the official death toll there remains at 556.

There were 23 new cases in the region, including the weekend figures, taking the total number of cases to 5,857.

Dr Glynn said: "This is an extremely infectious disease and it does not take much at all for this to spread."

He said when businesses reopened a few weeks ago, they went to great lengths to ensure their employees and customers were protected and it is understandable if that compliance has dropped off over time, but now is the time to ramp up those measures again.

The department said that 270 cases had been confirmed in the Republic over the past two weeks. It said that 43% of these cases were male, with 57% female.

The median age is 34 years old, with 69% of these cases under 45 years of age.

It said 20 counties reported new cases, with Dublin accounting for 55%, Kildare 10% and Cork 6%. All other counties were 5% or less.

Dr Glynn said 83 cases (31%) were in healthcare workers.

He said 1,110 deaths (63% of total) were associated with outbreaks in residential care facilities, of those 987 (56%) of all deaths have been associated with clusters in nursing homes.

There are 11 confirmed cases in hospitals, nine of whom are in critical care units.

Chief Nursing Officer at the Department of Health Rachel Kenna said: "Our healthcare workers have been at the frontline since March and they deserve our best efforts to continue to minimise the spread of this virus.

"The impact of any increase in cases will be hard on healthcare workers, who have already given so much to keep us safe this year.

"Let's reward their dedicated and unwavering service by holding firm on Covid-19."

Dr Sumi Dunne of the ICGP said: "Covid-19 is a highly infectious disease, it thrives in crowds. There is no blame in contracting the virus.

"Please stay alert and look out for common symptoms such as a cough or a high temperature.

"If you suspect you have the symptoms, isolate yourself from other people to contain the virus and come forward for testing by contacting your GP as quickly as possible."

Earlier today, Minister for Health Stephen Donnelly said the green list of countries safe to travel to will be published this week.

Minister Donnelly also said the public health advice on travel is the same as it has been from day one, which is do not travel abroad except for essential reasons.

Speaking at Leinster House, he said if people do have to travel abroad they must restrict their movements for two weeks.

Elsewhere, two coronavirus vaccine candidates have proven safe for humans and produced strong immune reactions among patients involved in separate clinical trials, doctors have said.

The first trial among more than 1,000 adults in Britain found that the vaccine induced "strong antibody and T cell immune responses" against the novel coronavirus.

A separate trial in China involving more than 500 people showed most had developed widespread antibody immune response.

The World Health Organization says data to date suggests 80% of Covid-19 infections are mild or asymptomatic, 15% are severe infection, requiring oxygen and 5% are critical, requiring ventilation.

Generally, you need to be 15 minutes or more in the vicinity of an infected person and within two metres of them, to be considered at-risk, or a close contact.