Gastroenteritis can be caused by viruses, bacteria, bacterial toxins, parasites, certain chemicals, and some drugs. Viral gastroenteritis (stomach flu) is caused by a virus attacking the digestive system. There are a number of viruses that can be responsible, but the most common are Norovirus, Rotavirus, Adenovirus, and Astrovirus. This form of gastroenteritis is highly contagious and is spread through improper handwashing (especially by food handlers), contaminated water, or eating undercooked or raw shellfish caught in contaminated waters. Bacterial gastroenteritis (food poisoning) is caused by cross-contamination of organisms due to improper food handling. Food recalls are often a result of outbreaks of bacterial gastroenteritis caused by contaminated food being served in restaurants or sold in grocery stores. Many bacteria can be responsible for causing bacterial gastroenteritis including: Yersinia, found in pork - Staphylococcus, found in meat, eggs, and dairy products - Shigella, found in water and frequently swimming pools - Salmonella found in dairy products, eggs, and meat - Campylobacter, found in meat and poultry - E.coli, found in salads and minced beef