Aids, hepatitis b and hepatitis c are caused by pathogens that are found in the blood of those infected?

Viruses: The infections you mention are all caused by viruses which get into the blood stream.

Viral Infections: Not sure what you are really asking or how this answer will in any way add to your medical knowledge. But, yes, of course. These three major viral illnesses are common and many of those infected have these viruses as chronic active infections in their blood stream. 80% of those adults who get hep b will clear the infection from their blood. New treatments for hep c can lead to cure.