That was the warning from chief medical officer Dr Tony Holohan in his letter to Government recommending Level Five restrictions.
The letter to Health Minister Stephen Donnelly says the rate of cases among people over the age of 65 has increased by more than 1,000 percent in the past two months.
NPHET says implementing Level Five now is the "only opportunity" to get the disease under control while keeping non-Covid healthcare operating and schools open.
Disease modelling shows that if current trends continue, 1600 to 2300 cases will be notified per day by November 7.
Dr Holohan wrote: “Disease modelling shows that if current trends continue, 1600 to 2300 cases will be notified per day by November 7.
“The modelling also shows 43 people with Covid-19 being admitted to hospital per day by that date. In light of the above, NPHET believes proactive and robust measures must now be taken so that very significant suppression of the disease with the reproductive number well below one is achieved.
"It is therefore recommended the government apply Level 5 measures across the country from midnight Monday, October 5, for a period of four weeks.”
Dr Holohan's letter was published on the gov.ie website around the same time as Taoiseach Micheál Martin addressed the nation last night, revealing Level Three restrictions would be rolled out for the entire country.
The letter went on to say there should be "immediate activation by all state agencies and other bodies of all necessary processes, plans, supports and measures to ensure the necessary services are available to those who need them over the coming four weeks”.
Dr Holohan said: “It is vital we do everything in our power now (underlined) to arrest the current trajectory nationally and very substantially suppress the virus back down to a low level of transmission in advance of the winter months."
He also said Level Five restrictions should be accompanied by “comprehensive and consistent communications”.
Dr Holohan added: “These communications should provide clarity on the measures in place, on why those measures are in place and on what each individual, organization, and employer can do to suppress the virus.”
