ATLANTA (AP) -- Americans suffered a bit less food poisoning last year.

There were significant drops in illnesses from shigella and the most dangerous form of E. coli, according to a government report released Thursday. But overall, food poisoning rates have been flat for more than five years.

The report is based on cases in 10 states that participate in a federally funded monitoring system of lab-confirmed infections that can be spread through food. They reported about 17,500 cases of the nine leading illnesses last year, down from about 18,500 in 2009.

More important to scientists are the rates of illness. The report from the Centers for Disease Control and Prevention noted a 12 percent decrease in the incidence rate for E. coli O157:H7 from 2008. The rate dropped to its lowest level since 2004.

That E. coli strain is a dangerous form of an ordinarily harmless family of bacteria that can cause abdominal cramps, fever, bloody diarrhea, kidney failure, blindness, paralysis, even death. Cases occur in about 1 in every 100,000 people.

The decrease was probably due to better safety measures in the meat and produce industries, health officials said.

Shigella (shih-GEHL'-uh) is a bacterial infection that is about four times more common. It also declined significantly, about 40 percent. However, only about 20 percent of shigella cases are thought to be caused by food. It's usually spread by person-to-person contact, with day care centers a traditional hot spot for infections.

That decrease may have been driven by unusually high amounts of hand-washing and disinfection because of the swine flu pandemic that broke out last year, said Elliot Ryser, a professor of food science at Michigan State University, who was not involved in the study.

"You might kill two birds with one stone" by hand-washing, Ryser said, referring to swine flu and shigella.

For other illnesses, the CDC reported:

- Salmonella -- the most common of the illnesses -- was down slightly, despite a national outbreak of peanut-related salmonella at the beginning of 2009.

- Vibrio, a rare illness associated with shellfish, continued to rise.

- Listeria also rose, despite efforts by the packaged meats industry to prevent the illness.

Deaths from these bugs are unusual. In the 10 states last year, salmonella was the deadliest with 24 deaths attributed to it. Listeria was second with 20 deaths. Vibrio was blamed in seven deaths, the dangerous E. coli strain in two and one from shigella, according to CDC data.

The study is being published in a CDC publication, Morbidity and Mortality Weekly Report.

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