Food and drinks can easily become contaminated with norovirus because the virus is so small and because it probably takes fewer than 100 norovirus particles to make a person sick.
Food can be contaminated either by direct contact with contaminated hands or work surfaces that are contaminated with stool or vomit, or by tiny droplets from nearby vomit that can travel through air to land on food. Although the virus cannot multiply outside of human bodies, once on food or in water, it can cause an illness called norovirus gastroenteritis.
Some foods can be contaminated with norovirus before being delivered to a restaurant or store. For example, several outbreaks have been caused by the consumption of oysters harvested from contaminated waters. Produce, such as salads and frozen fruit, may also be contaminated at the source.