A number of NI schools have issued advice on social media about how to be vigilant to and prevent the spread of the norovirus.
A spokesperson for the Education Authority said: "EA is aware of four individual schools who have or are planning to close to undertake a deep clean, as a precautionary measure following an increase in cases of general winter illnesses, such as diarrhoea and vomiting.
"The decision to close is taken by the individual school, unless otherwise advised by the Education Authority in conjunction with other statutory agencies."
Yesterday a post on Lurgan Junior High School Facebook page said parents need to be aware of "increasing cases of sickness in the local area".
"In order to minimise the impact on our school we would ask you to look at and follow this advice from the NHS:
It's not always possible to avoid getting norovirus, but following the advice below can help stop the virus spreading.
• Stay off work or school until at least 48 hours after the symptoms have stopped. You should also avoid visiting anyone in hospital during this time.
• Wash your hands frequently and thoroughly with soap and water, particularly after using the toilet and before preparing or handling food. Don't rely on alcohol hand gels, as they do not kill the virus.
• Further details and advice are available from CLICK HERE
Meanwhile on Twitter Clandeboye Primary school reveal they will be closed tomorrow in a bid to stem the spread of the virus.
"We will be closed tomorrow to allow for deep cleaning in an attempt to stem the spread of the winter vomiting bug," they write.
"We need to keep phone lines open and are asking parents to please refrain from telephoning school regarding pantomime refunds.
"We will deal with this in due course."
Meanwhile Killinchy Primary school headmaster Christopher Currie told Belfast Live their "worst day" has been today.
He said: "Our worst day is actually today (Tuesday) believe it or not.
"Even though we did the deep clean obviously whatever bugs these are, the kids already had them because they certainly didn't get sick today as the place was disinfected from top to bottom from Saturday through to Monday night.
"We sent 17 children home today. Across the Wednesday, Thursday, Friday outbreak we were 55 children down on absence which was crisis point and we decided to do a voluntary closure on Friday."
The Public Health Agency in NI said they are "aware of a number of schools that have seen an increase in children experiencing vomiting and diarrhoea or flu-like illnesses".
"While it is not unusual to see an increase in illness at this time of year, we are urging people to take simple steps to help prevent the spread of illness.
"Respiratory illness, as well as other illnesses such as vomiting and diarrhoea, can be very common at this time of year. For most people they are short-term, unpleasant illnesses, with most of us getting better within a few days. However, we can all play our part in keeping illnesses at bay and helping to protect more vulnerable people, for whom they can present a more serious risk.
"We would urge people to get the flu vaccine if eligible, take extra care with hand hygiene and, if you are feeling unwell, take simple steps to prevent the spread.
"· Carry tissues and use them to cover your mouth and nose when you cough or sneeze, dispose of the dirty tissues quickly and wash your hands regularly.
· Always maintain good personal hygiene, in particular wash your hands after going to the toilet and before preparing or eating food.
· If you are vomiting or have diarrhoea, don’t visit friends or relatives in hospital or residential and nursing homes, and avoid visiting your GP’s surgery – it is much better to phone for advice first."