New guidelines on how to deal with nursing home flu outbreaks, which were issued in recent months, point out the virus is very infectious and easily passed from person-to-person, leaving elderly people living at such close quarters at risk.
There can be seasonal rates of between 2-16pc among nursing home residents but an outbreak can see up to 40pc of residents struck down.
All residents and staff should get the flu vaccine annually and if there is an outbreak the infected people should be isolated and treated.
Staff should make themselves aware of the early signs of the virus and if there is an outbreak a special team should be set up to manage it.
An outbreak is defined as three of more cases of flu or suspected flu within 72 hours.
It emerged yesterday that the first resident of Nazareth House in Buncrana died on March 22. Two died on March 29, one on March 31, one on April 1 and one on April 2.
In case of an outbreak the local HSE public health unit should be notified and include specialists in infection control. Samples should be sent for testing to the National Virus Laboratory.
There should be active daily surveillance and all infection prevention and control measures need to be put in place.
Details of staff who become infected should also be included and there should also be a proper system of communications with residents' families and friends.