HIV can only survive in a body – it gets
destroyed almost immediately outside of a
person. The reason for that is that the virus
cannot replicate by itself – it utilizes the
human DNA for that. HIV implants its
genetic information into the healthy cell's
DNA, which subsequently starts acting like
a virus-producing plant. Eventually, the
exhausted cell dies, but not before
churning out multiple copies of the virus.
HIV utilizes the cells of the human immune
system for replication and that is why it is
so dangerous – the immune system is the
barrier that protects us from disease and
when it gets destroyed by HIV it makes our
bodies vulnerable to all sorts of nasty
infections.
Many
people think that HIV and AIDS is the same
thing. However, this is not so. When a
person gets infected with HIV, it starts
destroying his or her immune system which
is responsible for protecting the body from
infection. An HIV-infected person can carry
the virus for many years, looking and
feeling fine and not even know that he or
she is infected. However, eventually the
virus destroys so many of the immune
system cells that whatever are left are
incapable of effectively fighting off
infection. The AIDS (Acquired Immune
Deficiency Syndrome) diagnosis is made
usually in a few years (8 to 11 years on
average, however that time greatly varies
from person to person) after infection
when a person gets chronically sick with
diseases that are normally fended off by a
healthy immune system. For example, early
symptoms of AIDS include recurring fever,
night sweats, diarrhea, weight loss, acute
respiratory viral infections and herpes.

http://www.mediprimer.com/Immunology/hiv_aids/126.html
Below is a video of how the thing replicates


https://www.youtube.com/watch?v=v_AUuMbtO-E&feature=youtube_gdata_player