Final answer:
The diseases caused by organisms less than 5 microns in size include chicken pox, tuberculosis, measles, and influenza.
Step-by-step explanation:
The diseases caused by organisms (specifically viruses) that are typically less than 5 microns in size include chicken pox, tuberculosis (caused by bacteria which can be as small as 2-4 microns), measles, and influenza. Viruses, which are the pathogens responsible for chicken pox, measles, and influenza, are much smaller in size compared to most bacteria and are not visible under the light microscope. They can range in size significantly but are generally smaller than 5 microns. Tuberculosis, although caused by a bacterium (Mycobacterium tuberculosis), also fits into the category as the bacteria are generally within this size range.