Actually, what is stated is that the “maker says it “reduces up to 99.99999% of waterborne bacteria””.

The reason it is not 100%, is the accepted standard in microbiology that one cannot prove a negative (100% reduction/elimination), so a 99.999…% reduction or X log reduction is standard terminology.

You are correct regarding the need to treat water for viral contamination with heat, chemical or UV methods and not just a filter.

Pete