The World Health Organisation has warned that a pandemic outbreak is imminent
One man in the Republic of Ireland has tested positive for swine flu, initial tests have indicated.
The case is in an adult male living in the east of the country. It is understood the man had recently returned from Mexico.
Six people in Northern Ireland have been given anti-viral drugs as a precaution against the swine flu virus.
The results of tests on these cases are not yet known, while 14 people have now tested negative for the virus.
The Republic's Chief Medical Officer Dr Tony Holohan said all the people the man has been in contact will receive anti-viral treatment.
Professor Bill Hall, chairman of the National Pandemic Influenza Expert Group, said he was awaiting official test results.
"This is a probable case which is likely to be positive," he said.
Four other people in the Republic of Ireland have been given the all-clear.
Northern Ireland has been stepping up preparations to deal with a possible swine flu pandemic.
NI Health Minister Michael McGimpsey said masks and protective clothing were being sent out to doctors' surgeries and all should be equipped by Friday.
The move follows the World Health Organisation's (WHO) decision to raise the current level of influenza pandemic alert from phase four to five - indicating human-to-human transmission in at least two countries.
It is a "strong signal that a pandemic is imminent", the WHO says.
Mr McGimpsey said that the masks being sent to surgeries were equipped with respirators.
"The key advice is if you are feeling unwell don't go out of the house, stay at home, ring the GP and the GP will look after you," he said.
He added that the current medical advice was that the paper-type disposable masks featuring in coverage from the outbreak in Mexico would be of limited use in preventing infection.
"You would find a handkerchief just as useful," he said. "And it may give a false sense of security."
A Northern Ireland helpline has opened to give advice to anyone concerned about swine flu. The free-phone number is 0800 0514 142.
Acting Chief Medical Officer Dr Elizabeth Mitchell said: "The key message to the public is not to be alarmed but to be prepared for a potential pandemic.
Wash your hands regularly
Use tissues to cover your mouth and nose when you cough and sneeze
You cannot get swine flu from eating pork or pork products
"Evidence to date suggests that, other than in Mexico, the majority of cases have had a relatively mild flu-like illness which responds well to treatment with anti-virals.
"We have been planning for a situation like this for some years. In fact, the UK is recognised as among the best prepared for any potential pandemic.
"The preparations we have in place and are continuing to make, will help us respond well in the event of a pandemic.
"GPs across the country have been notified and made aware of the symptoms and what to do if they suspect a patient has pandemic flu.
"We have also purchased enough anti-virals to treat up to 50% of the population and are rapidly moving to buy enough to treat 75%."
An emergency control centre has been set up at Stormont to deal with any outbreak.
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