C. difficile infections have long been associated with young children in day care, although today more adults, especially the elderly, contract illnesses caused by this microorganism. This may be partly because of growth of the elderly population. People in high-risk situations are more likely than the normal population to contract infection. People living in long-term health facilities or nursing homes or in long-term hospital stays have higher risks of infection due to weakened immune systems. The incidence of C. difficile infections in hospitals has increased steadily, since the 1980s. Hospital-related cases doubled between 1993 and 2003, more than doubled between 2000 and 2005, and continue to increase today.

C. difficile inhabits the gastrointestinal tract, and outbreaks are due to fecal contamination of food or other items. Infections arise from eating food contaminated with fecal matter or from self-inoculating with fecal matter on surfaces or inanimate items. Self-inoculation involves receiving a microorganism into the body, usually by touching the hand or fingers to the face—specifically touching the mouth, nasal passages, or eyes. C. difficile occurs almost everywhere—in food, water, soil, and numerous surfaces in hospitals. The widespread incidence of the microorganism increases the chance of self-inoculation. Illness symptoms usually consist of watery diarrhea, bloody stools, fever, abdominal cramping, and nausea. These ailments can lead to dehydration and weight loss, and, in severe cases of intestinal inflammation, the infection can be fatal.

Infections caused by this microorganism have been associated with antibiotic treatment for other infections. C. difficile has developed resistance to a variety of antibiotics, since at least the 1990s. When a patient has been treated with antibiotics to stop any other type of infection, the antibiotic also kills a large number of normal intestinal bacteria that protect people against many infections. As the antibiotic wipes out these beneficial bacteria, resistant C. difficile grows to large numbers in the intestinal tract. It then, releases two toxins, each of which destroys the inner lining of the intestines. As a consequence, the intestinal lining inflames, causing a reduced ability to absorb nutrients and diarrhea. C. difficile has become so resistant to a variety of antibiotics and spreads so easily that it has been called a superbug, which is any microorganism that has evolved into a very virulent (capable of causing disease) and difficult-to-kill pathogen.

Abraham Sonenshein of the Tufts University School of Medicine said, at the 2007 meeting of the American Society for Microbiology, “The [C. difficile] genes responsible for toxin production only seem to be expressed during periods of nutrient deprivation. This is consistent with the view that most disease-causing bacteria express their pathogenicity when they are hungry.” Since 2002, a more virulent variety of C. difficile has emerged in U.S. and Canadian hospitals. This strain produces a higher level of toxin than typical C. difficile and causes a more destructive and deadly disease in humans.

C. difficile infections cause several thousand deaths in the United States each year, yet the illness is preventable in two ways: by limiting the use of antibiotics to only lifesaving situations and by practicing good hygiene. People who prepare meals, hospital patients, and health care providers must wash their hands before handling food or working with patients. Day care workers should also wash hands before pre paring any meals, before and after touching children, and after diapering infants. Disposable gloves help reduce the chance of transmitting C. difficile, but only if they are changed for each of these tasks.