I don't know where the information on the chart came from, but it is not accurate. I have sold filtration products for a living since 1986 and have viewed information from the medical field and other sources which will refute this information. A 99.99% HEPA filter is used where surgical procedures are done where the bone marrow becomes exposed to protect from post operative infection. This filter is 99.99% effective on a .3 micron particle. This efficiency is chosen to block bacterial contamination. The chart lists bacteria at 3 microns. Talk to the folks at CDC or an infection control doctor and see if they agree that 3 microns is the smallest size that bacteria can be found in.
I will also point out that a human being with 20/20 vision can see a 20 micron speck in good light if the speck is black and the background is white.
Dave Nowlin