Harry wrote:
> By talking to my family doctor, I got a rough idea what a virus is.
> There is one message I remembered from his words--there is no medicine for
> virus caused cold!
>> Does it mean virus is not killable by medicine? If so, why do I hear that
> medicine under development for SARS? Did I misunderstood him?
The basic problem is that a virus isn't much more than a set of genetic
instructions wrapped up in a protective coat that helps deliver the genes into
an appropriate host cell. When that happens, expression of those genes
begins, ultimately resulting in production of progeny virus particles and
(usually) destriction of the infected cells. The progeny virus particles then
spread out to infect surrounding cells and continue the process. The viral
genes cannot be expressed unless they are introduced into a living host cell
that provides the functions needed for expression and replication of the viral
genome. The real problem is that viral replication is carried out by normal
host cell functions, although those functions are now being directed by viral
information to make viral products, so the infected cell usually isn't
appreciably different than an uninfected cell. Anything that will block viral
replication in infected cells will also block normal host functions in
uninfected cells. (I have a treatment that will immediately stop the
replication of any virus causing the common cold. Unfortunately, hydrogen
cyanide also stops the functioning of every other cell in the patient's body.
Not a very good therapeutic outcome.)
All of this is contrasted with bacterial infections, for which we have a wide
variety of effective treatments/cures. Bacteria are capable of independent
growth, as long as their nutritional needs are met (they have all of the
functions needed to express and replicate their genomes). For pathogenic
bacteria, that usually means establishing themselves in a human host but many
of those bacteria can be grown on artificial media, if the media are rich
enough in the things the bacteria need. The bacteria really need the host
only to provide nutrients that are not easily available elsewhere. Bacterial
functions, in many cases, are sufficiently different from host functions that
drugs can be found that will block bacterial functions without dramatically
affecting the host.
--
Larry D. Farrell, Ph.D.
Professor of Microbiology
Idaho State University
