Ireland could be facing months of "stop-start" emergency measures until a coronavirus vaccine is available.
Chief medical officer Dr Tony Holohan said there could be a point reached where the current phase of the crisis was contained to an extent where restrictions can be lifted and we have a real-time testing regime in place.
However, if there was evidence of a worrying spread of the virus after measures were relaxed, the restrictions would have to be tightened again.
A virus vaccine is unlikely before the end of the year and may take longer.
It was "not an unlikely scenario", he said, adding it was impossible at this point to put a timeline on ending the measures, as suggested by Fianna Fail leader Micheal Martin.
He was speaking as the number of deaths from the virus rose to 235 after another 25 people - with a mean age of 80 - lost their lives.
The total consisted of 10 women and 15 men and 18 of the victims had underlying health issues.
Another 365 people tested positive for the virus, bringing the total confirmed cases to 6,074.
Dr Holohan said 147 patients were in intensive care and 27 patients had died in those units to date.
However, the number discharged had risen to 53. Most of those admitted to ICU had an underlying condition.
Senior HSE official Liam Woods confirmed that a number of the larger hospitals in Dublin now have all, or most, of their existing intensive care beds full, with patients suffering from the virus or other serious illnesses.
Earlier yesterday, the Mater Hospital confirmed all its critical care beds were occupied, but it still had capacity in its high dependency care beds.
Mr Woods said the big hospitals in the east were seeing evidence of surge, but added that there were still around 138 beds free and that did not take into account additional spaces that can be provided following the scaling up of critical care by hospitals.
Four in every five deaths from the virus occur in hospitals, and around one in seven people who are hospitalised are admitted to intensive care.
The European Centre for Disease Prevention and Control yesterday said it was not the time to start reducing distancing measures within the EU.
The assessment is likely to influence Ireland's expert group, the National Public Health Emergency Team, which meets tomorrow and is due to extend the current emergency measures for another two weeks.
The report said that "before considering the lifting of any measures, member states should ensure enhanced population and hospital-based testing and surveillance systems are in place".
These are needed to inform and monitor escalation or de-escalation strategies.
The watchdog also cautioned that the risk of hospitals not being able to cope with demand, even with restrictions, was high. It would be "very high" if insufficient mitigation measures were in place.
Meanwhile, GPs are concerned at the drop in patients seeking care for health issues unrelated to the coronavirus.
Roscommon GP Dr Madeleine Ni Dhalaigh, of the Irish Medical Organisation's GP committee, said family doctors were worried about the decline in "routine" presentations.
"People have not got simply healthier," she said.
"The reality is that many are simply ignoring warning signs and risking larger health problems down the line because Covid-19 has become our only focus of discussion or debate.
"We are now appealing to people to make contact with us. You can talk to your GP over the phone who can then assess your situation."
Leading ophthalmologist Prof Michael O'Keeffe, of the Mater Private Hospital in Dublin, feared some of his patients risked blindness if not treated and has now been given permission to see them free of charge.
He was caught up in the wrangle which followed the State takeover of private hospitals. Paediatric patients with glaucoma and other serious eye ailments needed treatment.