A further 1,066 confirmed cases of Covid-19 were diagnosed yesterday, along with three deaths.
The aim is to get the daily total down to around 100 cases a day by early December to allow the country open up again.
"We are now in Level 5 because the disease is at very serious levels and posing a significant risk to public health," Chief Medical Officer Dr Holohan said yesterday.
"We all need to stay at home, except for essential work and exceptional circumstances.
"If you are a confirmed case self-isolate at home, if you are a close contact of a confirmed case restrict your movements at home, if you are experiencing symptoms or believe you are a close contact, restrict your movements and contact your GP."
Professor Philip Nolan, chair of the Nphet modelling group, said the R number - which needs to be lower than 1 - is at 1.3 to 1.4 nationally.
"Our collective goal now is to suppress transmission of the virus and bring our case numbers to manageable levels," he said.
"If we work hard together, we should succeed in reducing cases to below 100 a day in six weeks' time."
Deputy Chief Medical Officer Dr Heather Burns told yesterday's Department of Health briefing that there were 14,404 Covid cases notified over the past 14 days.
She said 649 new outbreaks of the virus were notified in the week to the October 17 with 461, or 71pc, in private households.
There were six additional outbreaks in nursing homes and community hospitals which are HSE long-term facilities.
She said there were 33 open outbreaks in these settings with a total of 451 cases.
"The 14-day incidence was at three per 100,000 at the end of June, today it is 302 per 100,000 population," Dr Burns added.
"The risk of you being exposed to Covid-19 is now 100 times greater than it was four months ago."
In the first three weeks of October there were 60 deaths in confirmed and probable cases, of which 24 are linked to nursing homes.
There has been an overall total of 1,871 Covid-19 related deaths in Ireland.
It comes amid growing fears that nursing homes could be hit by a second wave of illness and death from Covid-19 as the virus sweeps across the country.
It comes as Tadhg Daly, chief executive of Nursing Homes Ireland, revealed there are now cases of the virus in an estimated 40 nursing homes across the country, almost a doubling in six weeks.
He revealed there is major concern that some nursing homes will be left bereft of staff due to the virus and said the HSE has to ensure there are support workers ready to step in.
Chief medical officer Dr Tony Holohan warned last night: "Nursing homes have done everything to protect residents but it is not realistic to expect that we will protect nursing homes while we have the scale of infection spreading as it is in our population."
HSE clinical director Dr Colm Henry said 35 of the 570 nursing homes are receiving extensive support from the HSE from Covid response teams.
There has been a lot learned about the way the virus affects nursing homes since earlier in the pandemic.
"In March and April we were becoming aware of the problem in nursing homes when people were becoming sick and dying," he said.
"But testing staff every two weeks now means that outbreaks are discovered earlier.
"We are finding it earlier now. But despite all of that infection control, education and management we are finding it is impossible to keep Covid-19 away from older age groups in congregated settings.
"Once it enters congregated settings it is every bit as virulent as it was earlier in the pandemic," he warned.
"Based on our experience, widespread community transmission results in spread to vulnerable groups in congregated settings.
"The single most effective measure to protect vulnerable groups, including nursing homes, is to reduce community transmission significantly. Every one of us has a role to play to achieve this."