Which foodborne illness is not considered highly contagious?

Nontyphoidal Salmonella is not considered highly contagious compared to the other options listed. This strain of Salmonella typically arises from contaminated food or water and often comes from improperly cooked or handled eggs, poultry, or other animal products. The transmission primarily occurs through the ingestion of contaminated food rather than person-to-person contact.

In contrast, the other options, such as Shigella spp., Salmonella Typhi, and Norovirus, are known for their high contagion potential. Shigella spp. is particularly noted for spreading easily from person to person, often through poor hygiene practices. Salmonella Typhi, which causes typhoid fever, is also highly contagious and primarily spreads through contaminated food and water or direct contact with an infected person. Norovirus, one of the most common causes of foodborne illness outbreaks, is famously contagious and can be transmitted through contaminated surfaces or food and directly from person to person.

Thus, while all these illnesses require food safety measures to prevent outbreaks, Nontyphoidal Salmonella's mode of transmission makes it less contagious in comparison to Shigella, Salmonella Typhi, and Norovirus.