For people who survived the contaminated-water disaster at Walkerton, Ont., the health effects did not necessarily end with the intestinal distress.

Those with severe symptoms at the time are significantly more likely to show high blood pressure and reduced kidney function years later, a research group reported on Friday in the Canadian Medical Association Journal.

The May 2000 outbreak — blamed on bacteria from cattle manure seeping into a haphazardly chlorinated water system — is the most famous in modern Canadian history. Seven people died and many others suffered acute gastroenteritis, with diarrhea, vomiting and cramps.

The Walkerton Health Study, formed to track the results of the outbreak, followed 1,958 adults with no previous known high blood pressure or kidney disease for about four years.

In that period, nearly 36 per cent of those who showed severe symptoms during the outbreak were diagnosed with high blood pressure, compared with 32 per cent of those with moderate symptoms and 27 per cent of those with none, the group reported. The trend with reduced kidney function was similar and the differences between the groups were statistically significant, it said.

The researchers, led by Amit Garg of the University of Western Ontario medical school, concluded that acute bacterial gastroenteritis requiring medical attention was associated with an increased risk of kidney and blood-pressure problems years later.

"Maintaining safe drinking water remains essential to human health, as transient bacterial contaminations may have implications well beyond a period of acute self-limited illness," the study said.