In 2011, Shannon McKenney, a singer from Burnaby, B.C., suddenly fell violently ill at a dinner party.

Thinking it was food poisoning, the now 51-year-old went to the emergency room with severe pain and nausea, only to be sent home with a diagnosis of the stomach flu.

But when her appendix ruptured days later, her condition took a life-threatening turn. Though she survived the ordeal, her health never fully returned to normal.

Doctors initially blamed the lingering symptoms on complications from her appendix. What none of them realized was that McKenney had just survived a hidden and dangerous battle with sepsis.

What is sepsis?

Sepsis is a severe condition that occurs when the body’s response to an infection damages its own tissues and organs.

It is also known as septicemia or “blood poisoning,” and is most commonly caused by bacterial infections but can also stem from viruses or fungal infections, according to the World Health Organization and the U.S. Centers for Disease Control and Prevention.

It can develop rapidly, often within hours if left untreated. It may lead to shock, multi-organ failure and death — especially if not recognized early and treated promptly.