The Acting Chief Medical Officer says the number of COVID-19 cases in Dublin could double over the next two weeks.
211 new cases were confirmed last night, with 121 in Dublin alone.
Dr Ronan Glynn delivered a direct message to people living and working in Dublin on what can be done collectively to "get where we need to be with COVID-19".
With the disease growing at approximately 4% per day in the capital, he said urgent action is needed.
He said that 104 daily cases are now being reported in Dublin, with 1,055 cases in the last two weeks.
This means that the 14-day incidence rate now stands at 78 per 100,000 of the population.
Dr Ronan Glynn said: "Our best estimate is that the R nought is now 1.4 and if nothing were to change, we would expect to see the number of new cases in Dublin double over the next 14 days.
"We are seeing lots of cases clustered in households, and these clusters are spread all across Dublin city and county.
He said the vast majority of cases are among young people and that fortunately, admissions to hospitals are low, while the proportion of cases that cannot be linked to other cases is similar to the rest of the country.
He added: "This provides a window of opportunity for us to bring the current trajectory of the disease under control.
"But to do so, we all need to act now to break the chains of transmission to ensure we can continue to live as optimally as possible with the virus, keeping our schools open, resuming non-COVID healthcare and protecting those who are most vulnerable in our society."
A direct message to people living or working in Dublin to explain where we are currently and what we can all do to get where we need to be with #COVID-19. Your individual actions really do matter. They all count. They do work. #HoldFirm [For Closed Captions, select "cc".] pic.twitter.com/fbZlexdOVl
— Department of Health (@roinnslainte) September 11, 2020
Dr Glynn asked people to take "positive action immediately" and to make "small but vital changes" to their current behaviour.
He requested that people commit to having fewer gatherings in their homes, to limit social contacts as much as possible, to avoid crowds, and see small groups of the same people regularly rather a variety from different circles.
He advised that people should be "attentive to safe practices", such as maintaining social distancing, washing hands and wearing face coverings.
He said: "I know you know the core messages but it's time that we double our efforts to stay safe."
Dr Glynn said there had been a large increase in the number of people availing of COVID-19 testing in recent weeks.
He added: "Your individual actions really do matter. They all count. They do work."
