By Lee Carter
BBC correspondent, Toronto
Canadian health officials are trying to cope with a bacterial infection found in hospitals and nursing homes.
Hospitals have felt the strain of various viruses, including Sars
It has been blamed for the deaths of a 189 patients in the past 18 months.
In a new study, infectious disease experts say cases of Clostridium difficile that causes diarrhoea and colon inflammation are increasing.
The newly published report says the incidence of the disease among the most vulnerable patients aged 65 and older has increased 10-fold.
C. difficile is a virulent strain of bacteria.
It grows in the large bowel and can persist in the body for months despite repeated antibiotic treatment.
Plea for more hygiene
The experts investigating the Canadian outbreak say the bacterium appears to have mutated into a highly contagious and lethal strain, but they do not know why.
It only seems to affect patients in hospitals and it usually strikes them after they have been given antibiotics for another condition.
It has been blamed for 100 deaths in one Quebec hospital alone in the past 18 months.
The risk of contracting the disease seems to increase for patients being treated with chemotherapy or abdominal surgery.
It can also be spread by spores mostly commonly found in toilets.
So far the disease has been confined to a handful of hospitals in the province of Quebec and the western city of Calgary.
Quebec's health minister has urged against panicking and questions whether all the deaths attributed to C. difficile can be directly blamed on the disease.
Health officials say they will set up a system to track C. difficile more efficiently and are urging all staff in Canadian hospitals to increase hygiene measures such as cleaning toilet seats and doorknobs and systematically washing hands.