Bacteria respond better to medications that attempt to eradicate the contagious illness than viruses do.
If you contract a contagious illness by coming in contact with infected blood, this would be considered contraction through direct contact.
Because protozoan infections are highly variable, doctors often use a different medication for each that is highly specific and effective against the certain type of protozoan.
(There are a lot more though)
:) Hope this helps some.
@mfaye_
