Around 45 litres of water that was infected with the polio virus leaked from a water purification plant at the factory. The leak is reported to have been caused by human error.
Public health official are keen to stress that the leak did not result in any great danger to the general public as polio is the only vaccine that is mandatory in Belgium and an estimated 96% of people living here have been vaccinated.
The Federal Public Health department advises anyone that has been swimming in or has fished in the River Laan/Lasne to contact their GP if they have any concerns.
The River Laan/Lasne has its source in the village of Plancenoit in the Walloon Brabant municipality of Lasne, it flows through Rixensart (Walloon Brabant) and then through the hamlets of Tombeek and Terlanen (Overijse, Flemish Brabant), before joining the River Dijle at Sint-Agatha-Rode (Flemish Brabant).