People in Walkerton, Ont. who fell ill during an E. coli disaster show no elevated risk of heart disease after a decade, researchers have found.

The tainted water outbreak in 2000 killed seven people and sickened over 2,300.

A dedication rock memorial in Walkerton, Ont. commemorating the 10th anniversary of town's E. coli disaster. Prescriptions for hypertension medications increased eight-fold among residents in the decade after the outbreak. (Nathan Denette/Canadian Press)

The town's water was contaminated with E. coli O157:H7, the same strain implicated in this fall's gastrointestinal outbreak involving beef from XL Foods across Canada.

Researchers from London, Ont. previously found Walkerton residents affected by E. coli had higher than expected incidence of hypertension and chronic kidney disease. At the time, residents self-reported cardiovascular disease, but that was based on their recall.

To more accurately determine the 10-year risk of death and cardiovascular events like heart attacks, kidney specialist Dr. Amit Garg of London's Lawson Health Research Institute, and his colleagues compared 898 adults in Walkerton to a group of more than 11,000 residents living in the surrounding communities who weren't affected by the outbreak.

"This study provides evidence that the risk of major cardiovascular events was not higher in Walkerton in the decade following the E. coli O157:H7 outbreak," the study's authors concluded in Monday's issue of the Canadian Medical Association Journal.

"This may be partly explained by active surveillance and treatment for conditions such as hypertension, which may prevent cardiovascular events."

Doctors closely followed affected Walkerton residents knowing that E. coli O157:H7 is notorious for damaging the kidneys and can cause high blood pressure.

Adults were followed for an average of 7.4 years, starting two years after the outbreak.

"In terms of health implications for the community of Walkerton these results are reassuring," Garg said in an email.

Prescriptions for hypertension medications increased eight-fold among participants from Walkerton compared with a three-fold among those in nearby communities.

It's possible that E. coli O157:H7 doesn't precipitate major cardiovascular events or that a decade isn’t long enough for the events to appear, the researchers said in noting the observational study can only point to a lack of an association rather than a lack of a causal relationship.

E. coli O157:H7 can cause diarrhea, bloody diarrhea, abdominal pain and fever.

The Walkerton Health Study is funded by the Ontario Ministry of Health.

Garg's team plans to continue following Walkerton residents for decades.