A spike of up to 70 Covid-19 cases in Co. Cavan has been linked to family who attended a wedding across the border, the Sunday World can reveal.
It is understood the family picked up the virus when they went across the border to attend the nuptials in Co. Fermanagh.
They then, unknowingly, infected a wider group of people on their return - much to the dismay of local public health officials.
There is no suggestion the family breached the Covid-19 regulations that were in place at time.
A source said: "They also had another family function in the Republic and gave it to people.
"They didn't deliberately go out and do it - they didn't realise they had it."
The numbers in Co. Cavan were among the highest in Europe when it reached a 14-day peak of over 1,000 per 100,000 of the population in the past few days.
Local doctors have been flat out for the past several weeks dealing with the outbreak.
A large number of cases were being blamed by GPs on post-match GAA celebrations as various inter club championships came to ahead.
One doctor told the Sunday World: "The border is another key factor with people moving over and back. Cavan people tended to traditionally congregate at weddings, funerals and football matches. They cross over and back into the North for work,school and shopping.
"There is a real community engagement here but, unfortunately, this kind of socialising is deadly dangerous when you are dealing with a pandemic."
Doctors and the HSE were stunned that the virus in Cavan had grown so fast so quickly.
One in 67 people in the region have recorded a positive test for the virus.
The Ballyjamesduff electoral area in Cavan currently has the highest 14-day incidence rate in Ireland 1,488.33 per 100,000.
Health Minister Stephen Donnelly also claimed the GAA in Cavan were partly to blame for the shocking Covid numbers.
Crosser Lough won the senior championship for the first time in 40 years while Ballinagh won the Intermediate title after a spell in the wilderness.
Only last week it came to light that a man in Limerick who had come back from abroad had infected 58 people in that county.
There were also reports in north Louth some local super spreaders.
The question of identifying and stopping super spreaders is a massive issue for the HSE trace and contact teams.
Cavan GP Dr Dara Hume warned: "Everybody needs to know to act like everyone they see and meet has Covid and stay well away from them.
"Just get it in your head that someone you love is vulnerable or at risk, like your granny or neighbour, and this is what you have to do to save them.
"I cannot comment on any individual cases, but definitely the border is part of the reason the Cavan numbers are so high."
Both the HSE and the Dept of Health refused to comment.