Outbreaks of diseases produced by intestinal viruses are a public health hazard. In the last few years, viruses in the Norwalk group because of their high incidence and viruses responsible for hepatitis A because they cause a serious illness have received the most attention.
Eating contaminated food is the transmission route for some viruses. Viruses reach food either through people who are infected or through carriers who do not show symptoms. The foods that are most frequently involved are those eaten raw or undercooked. It is important to stress that viruses do not multiply in food, but that it is a passive vehicle for transmission.
Normally there are not many virus particles in contaminated food. But bivalve shellfish, which feed by filtering the water that they live in, can concentrate the viruses that are present in the water. This problem is made worse because some shellfish are eaten raw or lightly cooked. In fact, there are many descriptions of viral disease outbreaks that have been attributed to eating oysters and other bivalves such as mussels and clams.
Viral gastritis was first discovered over 50 years ago in the Southern United States. The name Norwalk virus was coined because of the town where the outbreak occurred. However, hepatitis A is the most important viral infection associated with consuming shellfish. It is interesting to remark that due to its long incubation period —of approximately four weeks— it is often difficult to prove what virus was the transmission vehicle, since the food involved is no longer available for testing. So it is probable that the number of hepatitis A cases associated with eating shellfish is too low.
At the same time that hepatitis A cases are dropping in developed countries, viral gastroenteritis caused by the Norwalk virus is clearly increasing. This disease is associated with consuming raw shellfish, so it is recommended to cook this type of seafood. Cooking should be done properly, which means the food should be cooked in boiling water, and that the heat should reach the entire product.
Be aware that eating raw shellfish may pose a risk to your health.
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