The reproduction rate of the COVID-19 virus is now between 1.5 and 1.8 - the highest it has been since last March, NPHET has warned.

According to Prof Philip Nolan, chair of NPHET's Irish Epidemiological Modelling Advisory Group, the situation continues to deteriorate and the day-on-day growth rate is estimated to be between 7% and 9%.

"These data emphasise the need for us to be exceptionally careful over Christmas and to adhere strictly to public health guidance," he insisted.

According to the Department of Health's deputy chief medical officer, Dr Ronan Glynn, the current epidemiological situation "is the most serious it has been since last March".

"People should act at all times as if they or those they come into contact with are infectious. The disease has spread across all parts of the country and all age groups. We must act now to protect each other," he said.

Meanwhile, according to Dr Cillian De Gascun, director of the National Virus Reference Laboratory, preliminary data based on a selection of samples analysed from the weekend suggests that the novel variant of the virus from the UK "is present in Ireland".

"However, given the timeline of the samples analysed, it would seem that the novel variant is not solely responsible for the recent increase in case numbers seen in Ireland," he noted.

The comments were made after it was revealed that a further 938 cases of the virus have been confirmed in the Republic, along with 13 more deaths.

This brings the total number of cases here to 82,155 and the total number of deaths to 2,184.

Of the 938 cases, 300 occurred in Dublin, 110 in Cork, 72 in Limerick, 68 in Donegal and 41 in Kildare.

The 14-day incidence of the virus per 100,000 of the population up until December 22 was 153.2, however 11 counties were above this, with Donegal the worst affected, at 317.9.

Ireland is set to return to level 5 of the Government's COVID plan from December 24. For more information on this, click here.