A 43-year-old man in Cork was the first diagnosed case of community transmission of Covid-19 in Ireland.
The case was detailed in an article written by medics at Cork University Hospital and published in the Irish Medical Journal last month.
The man, who was a farmer, tested positive for the virus and was tested "outside the national guidance" on testing at the time.
It was later found that the particular strain in this case showed "very little difference" from the original strain from China's Hubei province.
The man presented to the hospital on 25 February; just a few days before the first case of the virus was confirmed here.
He presented with a headache and was found to have pneumonia. He later required a high level of ventilation in intensive care.
The man died almost a month after being transferred to another hospital in early March.
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The article, whose authors include Eamonn Faller, an infectious diseases specialist registrar at CUH, outlined how the man had no epidemiological link to any area where the virus was prevalent at the time or any link to a confirmed case.
These factors, coupled with the atypical presentation in an otherwise young and healthy person, led to a decision being made to test the man for Covid-19.
The article's authors said this patient represents the first case of community transmission of the virus in Ireland, and that identifying the case had "far reaching implications" in the management of the virus here.
The report said that the case "provided evidence of community transmission in spite of only six imported cases having been reported nationally at the time of diagnosis".
To date, epidemiological tracing has failed to identify the source of transmission in this man's case.
It said that the case resulted in "immediate changes" to the criteria for testing and "informed the national response" to Covid-19, which the authors said "suppressed the curve and saved countless lives nationally".
A community transmission case is generally accepted as meaning someone who gets the virus had no known contact with another confirmed case, nor travelled from a country badly affected by the pandemic, meaning the virus is moving freely in the community.