The most common foodborne diseases are infections caused by bacteria, such as Salmonella and Campylobacter, or by the Norwalk family of viruses. A foodborne disease outbreak is defined as a group of people developing the same illnesses after ingesting the same food. Most cases of foodborne disease are single cases not associated with a recognized outbreak. The great majority of food items which cause foodborne diseases are raw or undercooked foods of animal origin such as meat, milk, eggs, cheese, fish or shellfish. Every year, in the United States foodborne infections cause millions of illnesses and thousands of deaths.
Most infections go undiagnosed and unreported.
Some foodborne diseases such as botulism and trichinosis are becoming less common, while others such as salmonellosis are becoming more common. Thus, the spectrum of foodborne disease is changing. New infections not previously known to be foodborne diseases are emerging. Approximately 600-700 foodborne related complaints are reported each year to the Bureau of Epidemiology. Not all outbreaks or diseases are equally likely to be reported, and many cases of foodborne diseases are sporadic.