Stool sample results will not be in until late next week.
The water areas of Tesomajärvi, Tohloppijärvi, Kaukajärvi and also Suolijärvi will display warning signs against swimming at least until next week, Tampere city environmental and health chief Merja Bojang.
About ten other swimming spots in the area have been noted as potential illness risk zones. No warning signboards will be posted along the beaches of these places.
About 50 of the illness reports come from surrounding Ylöjärvi, Nokia and Pirkkala, according to the Pirteva environmental health management unit.
Many sick are children
As much as 70-80 percent of those who have fallen ill after swimming in the allegedly contaminated waters are children.
“Viruses spread quickly among children, who horse around and come into contact with one another, and because they may drink the swimming water,” Bojang says in a statement issued by the city of Tampere.
She also says that most of the stomach illness cases are from last weekend, and that given time, the worst of the contagious episode may be over.
“We need to give the waters time to recuperate and cleanse themselves,” Bojang says.
The city of Tampere will release an online report form for sick people to fill out if they should start experiencing symptoms.
Some 30 cases of stomach illness have also been reported by swimmers in lakes around Oulu, where it’s suspected that faeces may have contaminated the water.
Update: additional information on children added.
