Seven possible cases of the potentially fatal Weil's disease are feared among canoeists who had been boating in the Lucan/Leixlip stretch of the River Liffey, the Eastern Regional Health Authority said last night.
The ERHA says two canoeists have clinical symptoms of the disease and another five have non-specific symptoms which could turn out to be influenza or some other condition.
It will know today whether the two people with clinical symptoms actually have the disease.
Weil's disease is caused by the urine of rats and the public has been warned against swimming or boating in the Liffey in the Dublin area.
Anybody who has been swimming or boating in the Lucan/Leixlip stretch of the river is asked to contact their GP if they have had flu-like symptoms since October.
The ERHA says it has alerted the Irish Canoe Union to the situation.
The bacterial disease can cause high fever, severe headaches, chills, muscle aches, vomiting, red eyes, jaundice, abdominal pain, diarrhoea or a rash.
It can develop into kidney or liver damage, meningitis or respiratory or cardiac problems.