Foodborne viruses are not especially resistant to heat. Most virus outbreaks are the result of consuming foods that are not cooked, or are contaminated after cooking. Many viruses are very stable in the environment, but cooking is good at denaturing the proteins that protect the virus. That's why it's important to cook food, including seafood, thoroughly before eating it.

  On the other hand, it's true that viruses are resistant to cold. Chilling or freezing does not eliminate viruses.