Incidence of food borne diseases is going up in US primarily due to lax in hygienic habits, according to a study by Centers for Disease Control and Prevention.

More than 21,000 ailments and 18 deaths happened from the approximately 1,100 reported food-borne disease outbreaks in the United States in 2007, says the research released in the CDC's Morbidity and Mortality Weekly Report.

Lack of habits like hand washing by food handlers and the contamination of food by animal fecal matter is among the major reasons for the rising occurrences of diseases caused by food borne germs.

A total of 497 such outbreaks were caused by one particular bug while more than one food-borne germ was associated with 12 of the outbreaks. No particular food borne agent could be identified in more than half of the outbreaks, the CDC report said.

Among the food borne agents identified, norovirus was the most common cause at 39 percent. According to the CDC, report, infected food handlers who don't wash their hands well after using the toilet are the most common cause of such outbreaks.

Norovirus was followed by salmonella (27 percent), which are most often caused when food is contaminated with animal feces in animal-related foods such as beef, poultry, milk and eggs, but vegetables and other foods can also be contaminated, the CDC said. However, cooking kills this food borne bacteria.

Poultry-related food was identified as the largest source among the 235 outbreaks where one type of food was identified. Poultry caused 691 illnesses, while beef led to 667 illnesses and leafy vegetables were the source of 590 illnesses, the CDC report said.

"Knowing more about what types of foods and food borne agents have caused outbreaks can help guide public health and the food industry in developing measures to effectively control and prevent infections and help people stay healthy," says Chris Braden, acting director of the CDC's Division of Food borne, Waterborne and Environmental Diseases.