As many as 23 patients have died this month after picking up Covid-19 in a hospital, it emerged last night.
It follows revelations by the HSE that in some unnamed hospitals, which have suffered major outbreaks of the virus, half the patients with Covid-19 caught it after admission with another illness.
The pattern of deaths in recent months indicates one-third of fatalities may be due to outbreaks in hospitals and the others are linked to nursing homes and community settings.
The stark findings come as 28 more deaths were reported yesterday, bringing the fatality toll to 208 this month.
The youngest person who died was just 25 and the oldest 98.
Deputy Chief Medical Officer Dr Ronan Glynn last night warned there will be "difficult days ahead" as more people succumb to the virus in significant numbers.
However, there are now growing fears that a return to the workplace in high numbers will jeopardise the slowing down of the spread of the virus seen in recent days.
Prof Philip Nolan, who tracks the virus, told the Department of Health briefing that the daily number of new infections was 3,955 and we are seeing the beginning of a reduction in case numbers.
It is essential that we "keep this up" for long periods of time but Google location data for January 10 showed the level of attendance at workplaces was at 50pc, much higher than in the first lockdown.
"The concern is that over the next week people will be asked back in the workplace or they will drift back."
He appealed to employers to facilitate people to do their job at home and he asked people to abide by public health advice to work from home.
"If that does not happen and people don't keep the reduction in their social contacts to the levels they have been doing in the next week to 10 days then the decline in case numbers will not be maintained and the expected recovery in our hospital system we expect to see in the next few weeks will not happen."
Asked about the reopening of schools from February, Dr Glynn said while they were "very safe environments" the issue was the higher level of mobility they generate.
He said it will be necessary to see how the virus is spreading in the coming days before making recommendations.
Struggling hospitals are unlikely to see a peak for another seven days and they will be under intense pressure for weeks because of the length of time it takes to treat the disease.
Liam Woods, who oversees hospitals in the HSE, said there were 321 intensive care beds open yesterday with a capacity to increase the number to 350.
Prof Nolan said "even if things go well" there could be 800 Covid-19 patients in hospital at the end of the month with 100 to 120 in intensive care.
Around 23 people a day are now dying from Covid-19 related illness, having increased sharply, and there is a particular worry that while the incidence of the virus is falling in other age groups it is plateauing among the over- 65s.
The R number, indicating how fast the virus is spreading, is now around 1 or 1.3.
Dr Glynn said nobody is immune from the disease and one in three people in intensive care is under the age of 65.
The UK variant, which is more infectious, now makes up around half the cases and it continues to gain ground.
Dr Cillian De Gascun of the National Virus Reference Laboratory said: "It is not unusual for viruses to mutate.
"We have identified multiple different SARS-CoV-2 lineages in Ireland, and two of the three recently emerged variants of concern from the UK and South Africa."