A warning has been issued to mass goers to take certain precautions to avoid spreading the flu.
The Health Protection Surveillance Centre (HSPC) has recommended that members of the congregation avoid receiving communion directly on their tongue.
If this occurs, priests and Eucharistic ministers should clean their hands using an alcohol based hand gel.
Drinking from the chalice could also cause problems, and the report suggests dipping the wafer into the wine or passing it around in small cups.
The Sign of Peace poses less of a threat, but the report recommends that priests give church goers the option of an alternative gesture that doesn't involve hand contact - such as a smile or nod.
Some 55 people have died from the flu in Ireland in recent months, most of them elderly.