Hello roseangel,
One reason viral diseases are more difficult to treat than bacterial
diseases is because the antibiotics we use against bacteria do not
work against viruses. For example, penicillin and similar
antiobiotics work by affecting the cell walls that form a protective
layer around many bacteria. This works, because our cells do not have
such a cell wall, so we are not affected by the antibiotics. However,
viruses do not have such a cell wall either, so they are also not
affected. Other types of antibiotics work by blocking the machinery
in the bacterial cell that makes new proteins and DNA. Again, this is
effective because the enzymes used by the bacteria for these purposes
are different from our enzymes. Viruses, however, do not have much of
their own systems to do this, but instead put to work the enzymes of
the cells that they have infected. While there are a few antiviral
chemicals that will work against viruses, these usually have to be
tailored to match a specific virus, and at present only a few viral
diseases can be treated in this way.
You can read more about antibiotics and antivirals at Dr. Reddy's
Pediatric Office on the Web: http://www.drreddy.com/antibx.html
Another reason that some viral diseases less easy to treat is due to
the fact that some virus can insert themselves into the DNA of a cell
they have infected, and stay dormant there for months or years. This
is called latency. A latent virus is, to all purposes, invisible. At
times, the virus will become activated and cause an obvious disease.
However, some of the virus will remain latent, ready to strike at a
later time. This means it is difficult to rid the body completely of
the virus. One example of a virus that becomes latent is herpesvirus.
This virus can insert itself into the DNA of nerve cells and become
latent. When activated, it travels down the nerve to its end within
the skin. There it infects the skin cells and starts to multiply,
causing sores on the skin. Cold sores are one example of a herpes
infection, in which the virus stays latent within nerve cells at the
base of the neck. When it is activated, for example by sunlight, it
travels along the nerve to the mouth and there causes sores on the
lips. The chicken pox virus can sometimes become latent too, and many
years after the original bout of chicken pox it can cause shingles,
which is a ring of painful blisters around the waist.
You can see a diagram of how herpesviruses travel along the nerves on
Herpesite at http://members.aol.com/herpesite/trans.html (scroll about
halfway down the page). |
