An
infection
occurs
when
a
virus
or
a
bacteria
(
the
____________________
)
enters
another
organism
(
the
host
)
and
,
to
sustain
itself
,
replicates
inside
the
host
.
In
cases
,
this
contact
causes
____________________
.
.
Infectious
diseases
are
produced
by
agents
that
are
in
the
____________________
,
such
as
____________________
,
viruses
,
parasites
,
or
____________________
.
____________________
are
microscopic
disease
agents
that
are
____________________
to
other
living
organisms
.
The
____________________
____________________
cells
,
also
known
of
the
main
components
of
the
____________________
system
.
