Another patient has died in connection to the outbreak of a highly infectious strain of C. difficile in Niagara region, raising the number of related deaths to 16 in little more than a month.

A tenth patient died after being afflicted by the infectious stomach virus at the St. Catharines General Hospital, the Niagara Health System announced on Monday.

Four other deaths have been reported at the Greater Niagara General site and two others have been reported in a Welland hospital since the outbreak began in early May.

"We truly recognize the loss that the family and friends of this patient are experiencing and on behalf of our staff and physicians we extend our sincere condolences," Dr. Joanna Hope, interim chief of staff for the Niagara Health System, said in a statement.

"The patient had very serious underlying health issues and also had tested positive for C. difficile. The patient's death will be reviewed to determine what role C. difficile played or did not play in their death. This patient's death has also been reported to the Coroner."

The Niagara Health System says 66 cases of C. difficile have been reported at three sites across the St. Catharines and Greater Niagara area.

St. Catharines General Hospital has reported 40 cases since the outbreak was declared at the site on May 28. The Greater Niagara General Hospital has reported 14 cases and a hospital in Welland, Ont., has reported 12 cases since the outbreak alert was expanded June 23.

Sixteen people have died since the outbreak was first reported on May 28, most recently the patient at St. Catharines General. A patient at the Welland Hospital died on July 2.

The outbreak has sparked protests from locals decrying the region's health-care system.

A demonstration is being planned for Wednesday in front of the Greater Niagara General Hospital to demand answers on how the outbreak has managed to continue for so long.

Clostridium difficile, or C. difficile, is a bacteria that spreads through contact and causes severe diarrhea and other intestinal diseases. It is one of the most common infections in hospitals and long-term care facilities, often affecting the elderly or those with underlying illnesses.

The Niagara Heath System represents seven hospitals that serve 434,000 people between St. Catharines and Fort Erie, Ont.

The Ontario government dispatched an Infection Control Resource team to St. Catharines General last week to provide assistance in managing the outbreak.

The Niagara Health System says the results of the C. difficile death reviews will be made public once meetings with the patients' families are complete.

With files from The Canadian Press.