One of five canoeists with flu-like symptoms who it had been feared might have been infected with leptospirosis on the Liffey has tested negative for the infection, the Eastern Regional Health Authority said.
The infection can, if untreated, lead to the potentially fatal Weil's disease.
One canoeist tested positive earlier this week for leptospirosis, and a result is awaited on another who had clinical symptoms of the infection.
Both of these people were hospitalised.
Results are still awaited on four canoeists who have not been hospitalised and who may have the flu which can be confused with the rare leptospirosis. Leptospirosis can be treated effectively with antibiotics.
Only those boating or swimming in the Leixlip-Lucan stretch of the Liffey on or around October 13th were considered at risk.
As the incubation period passes, the ERHA is optimistic that new cases will not emerge.