There is a "clear change" in the way Covid-19 is spreading, with younger people now accounting for the vast majority of cases in this country.
All of the 23 newly-confirmed cases last night were people under 45 years of age with 15 under the age of 25.
The National Public Health Emergency Team (NPHET) says people need to take immediate care and caution.
Acting Chief Medical Officer, Dr Ronan Glynn, is appealing to younger people to be sensible if gathering this weekend.
"You can gather with six, ten, 20 friends and don't social distance, all of you can be seemingly healthy. It only takes one person in that group to be spreading Covid.
"All of the people in that group can be fine. Perhaps no one will get unduly sick but you cannot be sure that that won't be the case for all of their families and their loved ones.
Please think twice.
Dr Glynn said that it is not about targeting a particular age group or about blame but about protecting one another.
“There are a variety of contributory factors, some are linked to travel, directly or indirectly.
“Nine of these cases are also linked to groups that have met up.”
He warned that if people try to go back to where things were in January then "it is only a matter of time before we face significant problems with this disease".
Dr Glynn said, over the past 14 days, 187 cases have been notified, of which 140 have arisen during that period.
Of these cases, the median age was 34.
Dr Glynn said there currently 13 cases in hospitals, of which nine are in critical care units.
There have been 462 clusters of infection, of which 261 have been in nursing homes.
He said the clusters account for 7,411 cases, of which 5,832 are associated with nursing homes.
Dr Philip Nolan of the National Public Health Emergency Team says the reproduction of the virus may be on the rise again.
#CovidTracker app will help us reach more people, more quickly, with the right advice. It is another tool we have to continue to suppress #COVID19.— Dr Ronan Glynn (@ronan_glynn) July 7, 2020
Please download https://t.co/VpmAmC8FIA
Stay safe. Protect each other. pic.twitter.com/gcI8LE14q9
He says his team's best estimate is that every person infected is passing it on to at least one other person.
"For several weeks now, we have been looking at a decline in disease and reduced transmission and our numbers in the region of .5 "Our best estimate is, as you would expect from the number of cases we are seeing this week compared to last week, the reproduction number is at or just above one."
The Department of Health announced on Thursday that a further six people diagnosed with Covid-19 in Ireland have died.
It brings the total number of deaths linked to the virus to 1,743.