Which of the following is NOT a highly infectious illness according to HESSN?

The flu, while it can spread easily and cause significant illness, is generally not classified as a highly infectious illness in the same category as the others listed. Hepatitis A, Norovirus, and Salmonella are all recognized for their higher levels of infectivity, meaning that they can be transmitted easily from person to person or through contaminated food and surfaces.

Hepatitis A is especially contagious and can spread through consumption of contaminated food or water, or direct contact with an infected person. Norovirus is notorious for causing outbreaks, particularly in communal settings, due to its low infectious dose and ability to survive on surfaces. Salmonella bacteria can also spread rapidly through contaminated food, leading to foodborne illness.

In contrast, although the flu is contagious, it does not exhibit the same level of infectiousness or outbreak potential as the illnesses mentioned above, particularly in food service contexts. Therefore, it is correctly identified as the option that is not classified in the same highly infectious category.