The number of people who died from gastroenteritis -- vomiting and diarrhea -- doubled in the United States from 1999 to 2007, federal researchers found. A study by the Centers for Disease Control and Prevention used data from the National Center for Health Statistics to identify gastroenteritis-associated deaths from 1999 to 2007 among all U.S. age groups. Lead author Aron Hall, of the CDC\'s Division of Viral Diseases, said during the eight-year study period, gastroenteritis-associated deaths from all causes increased from nearly 7,000 to more than 17,000 per year. Adults age 65 and older accounted for 83 percent of deaths. Clostridium difficile and norovirus were the most common infectious causes of gastroenteritis-associated deaths, the report said. \"Gastroenteritis is a major cause of death worldwide,\" Hall said in a statement. \"By knowing the causes of gastroenteritis-associated deaths and who\'s at risk, we can develop better treatments and help health care providers prevent people from getting sick.\" There was a five-fold increase -- from approximately 2,700 to 14,500 deaths per year -- for C. difficile, a type of bacteria often associated with healthcare settings, primarily hospitals. Norovirus was associated with about 800 deaths annually, though there were 50 percent more deaths in years when epidemics were caused by new strains of the virus. Norovirus is highly contagious and spreads through person-to-person contact and contaminated food, water and surfaces.