Schools across the county have been hit by a severe outbreak of the winter vomiting virus.
The strong strain of the norovirus - which also causes diarrhoea - has affected a number of primary and secondary schools, even forcing one to send a "significant number" of pupils home early last week.
St Pius X College in Magherafelt had to alert parents and send students home after a "significant number" of pupils became unwell last Wednesday.
An ambulance had to be called for one student, although it is unclear whether this was connected to the sudden outbreak in sickness.
The school has been providing constant updates to pupils and parents and on Friday said a number of "precautionary and preventative" measures had been carried out.
In a statement posted on Facebook, the school said: "We have continued to follow all guidance regarding the recent sickness experienced by a significant number of our pupils.
"Additional precautionary and preventative measures have been carried out.
"We are advised that the school being closed for 48 hours will generally mean things will have settled by Monday.
"With regards sending your child back to school if they have been ill, please adhere to the guidance already posted from the Public Health Agency.
"We wish all pupils a speedy recovery and thank parents and guardians for their support throughout."
It is believed that around 60 schools across the province have been impacted by the virus, common at this time of the year.
A PHA spokesperson confirmed it was aware of an increase in children suffering from the bug.
They urged the public to take steps to help stop the spread of the illness.
The PHA spokesperson said: "The Public Health Agency (PHA) is aware of a number of schools that have seen an increase in children with from vomiting and diarrhoea or flu like illnesses, while it is not unusual to see an increase of illness at this time of year we are urging people to take simple steps to prevent the spread of illness.
"Respiratory illness as well as other illnesses such as norovirus 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, to 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.
"Advice on when to return to school after being unwell can be found at www.pha.site/returntoschooladvice"
Over recent days some schools across Northern Ireland have been experiencing a "high level of illness" and an increase in children experiencing vomiting and diarrhoea or flu-like illnesses, to the extent that they have had to close to allow for deep cleaning in an attempt to stem the spread of the winter vomiting bug.
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