The Limpopo water affairs and forestry department said yesterday that water in the Tubatse River had tested positive for cholera.
Tests were carried out on the river near Burgersfort.
Department spokesman Leah Matlala said tests showed that the water carried the bacteria.
"We advise communities in the area not to use water from the Tubatse River because it might lead to people contracting the water-borne disease," she said.
Matlala advised people to boil water or add one tablespoon of bleach to every 20 litres before using the water.
At the weekend Dilokong Hospital treated more than 70 patients for cholera.
Steelpoort River was free of cholera, Matlala said.
"But people should take the necessary precautions when using the water," she warned.
The department is providing communities with water tankers.
Cholera was first identified in Zimbabwe on November 15. Limpopo's official death toll stands at nine.
Limpopo's health department said yesterday it had seen 1802 cholera cases.
Spokesman Phuti Seloba said 11 new cases were recorded in Dilokong yesterday, nine in Botlokwa, six in Lekhureng, 10 in Kutama-Senthumule and four in Madimbo.