According to information from the Centers for Disease Control and Prevention (CDC) concerning norovirus, statistics indicate that about 23 million cases of acute gastroenteritis have been due to norovirus infection. Among the 232 outbreaks of norovirus reported to the CDC from July 1997 to June 2000, over half were foodborne in origin. These and other norovirus statistics show that proper food handling and preparation methods are crucial in helping to prevent norovirus infection.
The Centers for Disease Control and Prevention (CDC) estimates that 23 million cases of acute gastroenteritis have been due to norovirus infection, and it is now thought that at least 50 percent of all foodborne outbreaks of gastroenteritis can be attributed to noroviruses.
Among the 232 outbreaks of norovirus illness reported to the CDC from July 1997 to June 2000:
- 57 percent were foodborne
- 16 percent were due to person-to-person contact
- 3 percent were waterborne.
In 23 percent of outbreaks, the cause of norovirus transmission was not determined.
In this study, common settings for norovirus outbreaks included:
- Restaurants and catered meals (36 percent)
- Nursing homes (23 percent)
- Schools (13 percent)
- Vacation settings or cruise ships (10 percent).
Most foodborne outbreaks of norovirus illness are likely to arise though direct contamination of food by a food handler immediately before its consumption. Outbreaks have frequently been associated with consumption of cold foods, including various salads, sandwiches, and bakery products. Liquid items (for example, salad dressing or cake icing) that allow the virus to mix evenly are often implicated as a cause of outbreaks. Food can also be contaminated at its source. For example, oysters from contaminated waters have been associated with widespread outbreaks of gastroenteritis.
Other foods, including raspberries and salads, have been contaminated before widespread distribution and subsequently caused extensive outbreaks.
Waterborne outbreaks of norovirus disease in community settings have often been caused by sewage contamination of wells and recreational water.