health

Hygiene and sanitation The first step in preventing the spread
of viral infections is simply to practice good hygiene. Doing so involves
washing the hands often, and eating only food that has been prepared
properly. It also involves building and maintaining facilities for getting rid
of sewage safely and for providing clean drinking water.


Vaccination Another important preventive measure is immunizing
people against viruses. Immunization involves giving people vaccines that
stimulate the immune system to make antibodies, proteins that target a
specific germ. Vaccines to prevent hepatitis B, polio, mumps, measles,
rubella (German measles), and chickenpox are usually given to babies and
young children in the United States. Vaccines also can prevent influenza
and hepatitis A.
Vaccines are useful only against certain kinds of viruses. For example,
the polioviruses that cause poliomyelitis (polio), a great crippler of children
in the past, are few in number and relatively stable. So it was possible
in the 1950s to make a vaccine that protects children from getting polio
(although the illness still occurs in the developing world where fewer children
are vaccinated). By contrast, influenza viruses change in minor ways
every few years and in a major way about every ten years, so a flu vaccine
is useful for only a year or two.
One reason a vaccine for the common cold has never been developed
is that there are at least a hundred different rhinoviruses that cause colds,
and as of 2009 it had not been possible to make a vaccine that works
against all of them. A similar problem with HIV, which has many different
and fast-changing strains (variations), is one of several reasons why
progress toward an AIDS vaccine was slow.