Deaths from gastroenteritis, or "stomach flu," more than doubled between 1999 and 2007, according to new research from the Centers for Disease Control and Prevention.

The rise was partly due to a fivefold increase over the study period in deaths from one cause of gastroenteritis, the bacteria Clostridium difficile (C. difficile).

The number of people who died from gastroenteritis caused by C. difficile rose over the study period from approximately 2,700 to 14,500 per year. C. difficile accounted for two-thirds of all gastroenteritis deaths over the study period.

Gastroenteritis involves inflammation of the stomach and intestines that causes vomiting and diarrhea.

Over the eight-year study, gastroenteritis deaths from all causes increased from nearly 7,000 to more than 17,000 per year. Adults over 65 years old accounted for 83 percent of deaths.

C. difficile and the stomach virus norovirus were the most common causes of gastroenteritis deaths.

Much of the recent increase in the number of cases and mortality of C. difficile is attributed to the emergence and spread of a more virulent, resistant strain of the bacteria, the CDC said.

Norovirus was associated with about 800 deaths per year, 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. Norovirus causes more than 20 million illnesses annually, and it is the leading cause of gastroenteritis outbreaks in the United States.

“While C. difficile continues to be the leading contributor to gastroenteritis-associated deaths, this study shows for the first time that norovirus is likely the second leading infectious cause,” said study researcher Aron Hall, of the CDC's Division of Viral Diseases. "Our findings highlight the need for effective measures to prevent, diagnose and manage gastroenteritis, especially for C. difficile and norovirus among the elderly."

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