The diocese of Down and Connor has suspended the "sign of peace" between people at mass in response to the surge in flu cases.
Priests in the diocese are being advised to disinfect their hands before they distribute Holy Communion.
Parishioners who think they may have flu are being asked to stay away from mass.
Fr Martin Magill of the Saint John's parish in West Belfast said he believes people will understand the need for the precautions.
During the week, health authorities in Northern Ireland warned of a possible increase in the flu virus which affected Australia last year.