Where did viruses come from, according to Young Earth Creationists? Viruses are quite nasty germs. Whereas bacteria serve many useful purposes and we need them, I wonder what the purpose of viruses in God's creation could be. Does Young Earth Creationism address what role viruses have in the world?

I'd like to hear the YEC view on the following points:


Where did viruses come from?
What is their purpose?
Were viruses created? If so, by whom?
Does the Bible say anything applicable?


If the Old Earth Creationist view is significantly different, please notify me. I expect them to be similar, but might ask another question focused on OEC if relevant.
The notion that all viruses are bad is worth challenging. In 2008 paediatrician Dr Lawrence D. Rosen, MD published a blog post entitled Viruses and Health: Not all bad? which looked at two interesting cases and concluded:


  In both of these cases, it appears that viral infections may indeed
  confer some sort of protection or health benefit to the host.  Is this
  true in all circumstances?  Of course not.  But the converse - that
  these viruses are always a health threat in all people, is equally
  unlikely.  It behooves us to be very, very careful when considering
  eradicating viruses from our bodies, particularly when the cure is
  potentially worse than the infection.


In addition, cancer research scientists are now looking at using (modified) viruses in order to combat this disease.ScienceDirect | Montana State University

Viruses are not mentioned in the Bible and whether they are technically living things is subject to continued discussion. In terms of their origin, the regressive and cellular hypotheses therefore don't entirely conflict with the Christian view; however the predominant view among creationists is that viruses are part of the original creation. Along with the rest of Creation, viruses were subject to The Fall, corrupting their original intended nature. The examples above show that viruses may be (or may have been) beneficial to health. In addition there is a theory called the Horizontal Gene Transfer (or horizontal gene flow) which may explain to some degree a purpose for viruses:


  that genes picked up from somewhere in the environment rather than
  inherited from parents may help to explain rapid adaptation and the
  interesting pattern of DNA in animals.Answers in Genesis: Why Did God Make Viruses?