Final answer:
Shigellosis must be reported to the regulatory authority as it is a significant foodborne illness caused by the Shigella bacterium, which is transmitted frequently through contaminated food and water.
Step-by-step explanation:
The confirmed food worker illness that must be reported to the regulatory authority is shigellosis. Shigellosis is associated with a rod-shaped, gram-negative bacterium called Shigella, which causes infections known as bacillary dysentery. It is a significant public health concern because it can be spread through the fecal-oral route, often via contaminated food and water. Regulatory agencies, including local, state, and federal levels, require the reporting of certain pathogens known to cause foodborne illness, and Shigella spp. is among the pathogens that are of the highest concern.