Take a crowd of people and put them in an enclosed space for several days and chances are some of those people are going to get sick.
Repeat the experiment in another building blocks away and some of these people will get sick too. They might even get some of the same illnesses that the people in the first building came down with.
However, these illnesses would not be related — unless some of the people from the first building also went to the second one. It's the same with hospitals battling outbreaks of C. difficile.
"It's already in other hospitals," Dr. Allison McGeer, director of infection control at Mount Sinai Hospital in Toronto told CBC News.
"It's not going to start in one hospital and spread like wildfire across the province. On the other hand, so far this year across the province the numbers of C. difficile are up."
It's a problem that's proving difficult to tackle, McGeer says. "Ontario's had for nearly two years a program that's been apparently quite effective against C. difficile — the numbers went down in the first 18 months. But for the last five or six months, the numbers are up again."
The strain of C. difficile that's now hitting Ontario hospitals first appeared about a decade ago. It caused a huge outbreak in Quebec that ended up killing 2,000 people in 2003. Another large outbreak in Ontario killed 62 people five years later.
It's a nasty bacteria that secretes an unusually high level of toxin. In the process, the colon becomes swollen and can burst, causing death from septic shock. Up to 10 per cent of patients infected will die from it.
The Public Health Agency of Canada only started requiring hospitals to report C. difficile deaths in 2009 and it is believed that 250 people in Ontario alone will die from it this year.
Many more will die from other causes, but C. difficile will be a contributing factor.
'This is really an opportunistic infection' —Dr. Karl Kabasele
Healthy people can become infected, but the vast majority of people who come down with it are elderly, have weakened immune systems, or have had abdominal surgery.
It is also closely linked with the use of antibiotics.
Besides being vigilant about handwashing when you are in a hospital, there is little you can do to protect yourself. The bacteria can live for days on doorknobs, elevator buttons and other common surfaces.
"This is really an opportunistic infection," Dr. Karl Kabasele, the CBC's medical specialist, explains. "When you are healthy and all is going well, you have benign helpful bacteria in your intestines and when you take antibiotics, or when you are sick, that flora gets disrupted, and things like C. difficile can take over and they multiply and create a toxin and that is where the symptoms come from."
Getting the upper hand on C. difficile, Kabasele says, involves instituting strict handwashing and hand-hygiene procedures to reduce the risk of people acquiring it themselves or passing it along to others.
Other measures include sanitizing surfaces, isolating patients who have the disease, and limiting the comings and goings of people into an affected room, or perhaps even into the hospital or long-term care facility.
Dr. Sue Matthews, president and CEO of the Niagara Health System, told a news conference that its hospitals are restricting the number of visitors, hiring more cleaners and bringing in two infection-control teams to help get the problem under control.
'It's about making sure that when we build hospitals, we build them right, with private rooms as opposed to people sharing rooms and bathrooms' —Dr. Allison McGeer
Dr. McGeer says getting the upper hand is a very complicated process that's going to take time to work through.
"It's about antibiotic use and how we help keep antibiotic use as low as we can while still giving the patients who need antibiotics the right antibiotics.
"It's about cleaning in the hospital — not just the floors and the elevator buttons but all of the complicated electronic pieces of equipment that we use to take care of patients. It's about making sure that when we build hospitals, we build them right, with private rooms as opposed to people sharing rooms and bathrooms."
In the end, it's all about money, McGeer says. Should scarce health-care dollars be spent on treatment or prevention?