Covid-19 is on course to strike up to 1,000 people a day in only a month, more than half of whom will be in Dublin.
There is growing alarm about the resurgence of the virus, not only in Dublin but in other counties, particularly Louth, Waterford and Donegal.
The grim forecast of between 500 and 1,000 cases a day emerged last night as doctors warned it is again spreading at a worrying level among older age groups and leading to more deaths.
"The rest of the country is on a similar trajectory to what is being seen in Dublin. People across the country need to act at an individual level," they told the Department of Health Covid-19 briefing.
Professor Philip Nolan, who is tracking the virus, said: "I am more concerned than I have been at any point since late April.
"If we do not interrupt transmission now, we could have 500 to 1,000 cases per day by October 16, some 50 to 60pc of which would be in Dublin."
He was speaking as 254 more people were diagnosed with the virus yesterday, with three more deaths.
However, he also warned that the virus is ominously spreading in other parts of the country and there are worrying trends in Louth, Waterford and Donegal.
There were 136 new cases yesterday in Dublin, 20 in Donegal, 13 in Louth, 12 in Wicklow, nine in Waterford, seven in Carlow, seven in Cork, six in Galway, five in Kerry, five in Wexford and the remaining cases were diagnosed in Clare, Kildare, Kilkenny, Laois, Leitrim, Limerick, Longford, Mayo, Monaghan, Offaly, Ros- common and Westmeath.
Prof Nolan and acting chief medical officer Dr Ronan Glynn appealed to everyone to reduce the number of people they meet during the day and to cut down on activities while practising the basics of physical distancing, hand washing, wearing a mask and contacting their GP if they have any symptoms.
Among the most disturbing trends is the rise in hospitalisations and deaths.
There were 73 patients with Covid-19 in hospital yesterday, nine of whom were admitted in the previous 24 hours. Fourteen of the patients are seriously ill in intensive care.
Prof Nolan said the hospitalisations are heavily concentrated in Dublin, where 50 patients are now in wards after being admitted with the virus.
The National Public Health Emergency Team (Nphet) will meet today to discuss the crisis in Dublin and nationwide.
It is expected Dublin will be moved up from Level 2 to Level 3 of the Government's Covid-19 plan, which will see a range of new restrictions, including restraints on indoor dining in restaurants and pubs as well as in areas like sporting activities.
The spread of the virus in Dublin is particularly concerning because it is due not to flare-ups in a particular workplace but to clusters across the city, often in people's homes.
"We are seeing many, many small clusters in the city and county," Prof Nolan said.
He said four people died of Covid-19 in August, but already this month 14 have died from the virus. The deaths are in older people in the community rather than in nursing homes.
The R number, which indicates how many people someone infected with the virus will pass it on to, is between 1.3 and 1.7 nationally. It needs to be at 1 to bring the spread under control.
The public health chiefs said the message to people needs to be not what they can do but what they "should do".
Dr Colm Henry of the HSE said the reopening of schools has been successful.
There have been around 300 cases of the virus among children, but only in around two or so of these was the infection picked up in the classroom.
Dr Mary Favier, Covid-19 advisor to the Irish College of General Practitioners, said: "While we have been conducting a large number of tests on children, thanks to the vigilance of parents around symptoms and contacting GPs with concerns, we have not witnessed a disproportionate rise in the number of confirmed cases in children."