The Centers for Disease Control and Prevention estimate that one in every 20,000 eggs is internally infected with salmonella based on data from the 1990s. That means that out of 100,000 eggs, about 30 would be infected. Eggs that are not properly cleaned or sanitized can allow salmonella to live and contaminate other food products. While this risk exists with any kind of food product, it's especially important with eggs because they can become contaminated at different stages in their production process. For example, hens can contract salmonella from eating or drinking water that is contaminated with animal feces or from eating feed that has been contaminated by animal waste.