The number of 'flu-like illnesses has almost doubled in Ireland in the past two weeks, the monitoring body for disease has said.
The Health Protection Surveillance Centre (HPSC) urged people in high-risk categories to get vaccinated against influenza due to the rise in the number of reported cases of influenza-like illness (ILI).
In recent weeks, the number of ILI cases has risen to 44.5 per 100,000 population from a previous rate of 22.5 per 100,000, the HPSC said.
"As influenza is now circulating in the community, it is important that people in high-risk categories get vaccinated against influenza," said HPSC specialist in public health medicine Dr Joan O'Donnell.
High-risk categories include those over 65, people with severe illness such as chronic heart disease, chronic lung disease and diabetes, those with lower immunity due to disease or treatment, healthcare workers and residents of nursing homes.
"The symptoms of influenza infection usually develop over a matter of a few hours and include a high temperature, sore muscles, dry cough, headache and sore throat.
"This is different from the common cold, which tends to come on more gradually and usually includes a runny nose and a normal temperature. Anyone in one of the high-risk categories should contact their GP if they develop influenza symptoms," said Dr O'Donnell.
According to the HPSC, ILI rates give an indication of the overall level of influenza activity in Ireland.
They are reported by selected general practitioners as part of a surveillance system jointly run by the Irish College of General Practitioners, the National Virus Reference Laboratory and the HPSC.
The weekly reports and further information on influenza and flu vaccine are available at www.hpsc.ie