Ireland's health ministry on Friday reported the country's first death linked to swine flu in a young woman with "an underlying health condition."
The woman died in Tallaght hospital in the south of Dublin, the ministry said.
A spokesman said she was suffering from "an underlying health condition" but provided no further details.
Her family has asked for privacy, the spokesman said.
Tallaght hospital said in a statement that the woman had been in an individual room from the time she was admitted.
"All national protocols have been followed in regards to this matter. The hospital's Influenza Pandemic Flu Committee have put in place all necessary measures to ensure both the safety of other patients and staff within the hospital."
The hospital said that to protect the confidentiality and privacy of the family it would not be providing any personal details.
"We can say that the patient in question was a young female adult who had an underlying health condition," it added.
Ireland's health surveillance system shows flu-like illness rates have increased in recent weeks.
In the seven days to Sunday, the incidence of the A(H1N1) virus was 32.5 per 100,000 people, the equivalent of some 1,400 cases nationally.
Last winter, the peak for the flu-like illness rate was around 120 per 100,000.
Ireland confirmed its first case of swine flu on May 2 when a man was found to be infected after returning from Mexico.