The shigella bacteria causes severe diarrhea, fever and abdominal cramps in humans and infects about a half-million people in the U.S. every year. Creative Commons

The rise of a drug-resistant superbug in Canada has health officials on edge. The severe stomach bacteria, called shigella, sickens thousands of Canadians every year and has become increasingly defiant to antibiotic treatment, prompting concerns of a serious public health threat. Of the total number of shigella cases in Canada last year, 243 were of an antibiotic-resistant strain, CTV News reported.

Outbreaks of shigellosis -- an infectious disease caused by shigella -- are typically linked to travelers who contract the bacteria in Asia or South America and then bring it back home. "The resistance seems to be increasing both internationally, but also here in Ontario and in Canada over the last five years," Dr. Vanessa Allen, chief of medical microbiology for Public Health Ontario, told CTV.

Health experts say the bug should always be treated with antibiotics. "With other bacteria, like salmonella for example, you can let it go and run its course. But all the guidelines suggest you treat shigella because it's so much more severe," Allen said.

Symptoms of shigella infection include severe diarrhea, fever and abdominal cramps. The nasty bug is passed from one person to another through infected food and water. Most shigella cases resolve themselves, however many patients often receive antibiotics to reduce the duration of symptoms. In the U.S., shigella causes roughly a half-million cases of diarrhea annually, the U.S. Centers for Disease Control and Prevention said.

Health officials have known about shigella’s increasing resistance to antibiotic treatment, but the problem has only gotten worse. Five years ago, only about 5 percent of shigella cases in Canada were of the drug-resistant strain. In 2014, that figure jumped to 14 percent, CTV reported.

More than 18,000 patients in Canada become infected with some form of a drug-resistant superbug every year, the Globe and Mail reported. Health officials estimate the annual cost of fighting such bacteria at about $1 billion in medical care expenses. Today, one in 23 patients hospitalized in Canada is expected to become infected with a superbug.