New figures show a surge in the numbers of people contracting Covid-19 while in hospital.
The Health Service Executive said that up to the end of last year 967 people had caught Covid-19 in hospital.
However, the HSE told RTÉ's Prime Time that the figure has increased dramatically in the past three weeks.
Since 27 December 846 patients have caught Covid-19 in hospital.
The HSE said when community transmission rates are at the level they are, it is "inevitable and unavoidable that there will be outbreaks in hospitals".
HSE National Lead for Health Care Associated Infection Professor Martin Cormican said there is concern about Covid-19 spreading in hospital settings.
He said he cannot guarantee if someone goes to hospital they will not contract Covid but that hospitals are doing everything to keep people as safe as possible.
He said an enormous amount of work has been done to keep them as safe environments but "obviously that didn't work well enough" for lots of people.
He said they have worked very hard to ensure there has been increased training for staff, increased access to PPE and also a huge amount of work by cleaning staff.
Prof Cormican said the news of Covid-19 outbreaks in hospitals is "most disappointing".
He acknowledged that how busy staff are during this pandemic is part of the challenge and said having colleagues who have contracted the virus and been off work has added to that pressure.
"The human factor is central to it. We have colleagues who work extremely hard who avoided infection for months and then caught it, but not sure where," said Prof Cormican.
He said the "slightest slip" is enough to catch it, describing it as the "very unforgiving enemy".
Prof Cormican said they encourage patients to wear masks away from their bed-space but many find it hard to wear them all of the time.
"It is not something you can impose on people."