Viruses
 
Screen 1 of 3
Viruses
are
very small
particles
 
that
can
infect
animals
 
 
and
plants
 
and
make
them
sick.
 
Viruses
are
made up
 
of
genetic materials
like
DNA
 
 
and
are
protected
 
by
 
a
layer of protein.