Almost 20 members of one family who live in small border village have tested positive for coronavirus after gathering to mark the one-month anniversary of a relative who died from the illness.
The family, who live on the Republic side of the border, lost an elderly relative four weeks ago and some of the extended family recently got together to commemorate her passing.
The virus is believed to have spread among those who gathered, who returned to their respective households and passed it on to other family members, including several young children.
It comes as figures show the number of clusters being detected in private households in the Republic is rising rapidly.
Figures from the Health Protection Surveillance Centre (HSPC) show an 87% increase in the number of clusters in private dwellings in the last week.
There were 390 outbreaks attributed to private households on June 21, compared to 728 cases one week later on June 28.
A cluster is defined as two or more people being infected with the disease in one location.
Dr Jack Lambert, a specialist in infectious diseases at the Mater Hospital in Dublin, said the public needs to "get back to basics" when it comes to preventing infection.
"There is a lot of talk about bringing Covid in from other countries but there is still Covid in Ireland," he said.
"But there are still infections among people who haven't travelled and that continues to be a risk.
"As soon as we let down our guard, be it with social distancing, or handwashing, or wearing masks, then it's a no-brainer that the infections will flare up again.
"We need to get back to basics. If you are in a family gathering all of the basics apply.
"If you are congregating and not socially distancing and there is one person in the room who has Covid and doesn't know it then everyone in the room is going to get it. That's what's happening already."
As the country re-opens, Dr Lambert warned that public complacency could lead to further spikes.
"This is a new virus that we don't know exactly how contagious it is," he said.
"One person can spread it to three others. One person with no symptoms can spread it to 10 other people."