Page 40 - cosmos4

Whenever a viral outbreak happens in various parts of the
world, we often wonder: Why is it that even though modern
science and technology can achieve so much these days, it
is still difficult for the scientific community to find a permanent
solution for any such pandemic? Why does it take time to
find a vaccine for a particular virus even though almost every
country in the world is competing for the same? One major reason is that Viruses

are part of the earth for a much longer period on earth, compared to human beings
whose presence is quiet recent, compared to existence of microbes. Viruses have
undergone their own evolution cycle. Viruses have had
enormous impact on humans and other organisms, yet very
little was known about their nature until fairly recently.

Viruses are a unique group of infectious agents whose
distinctiveness resides in their simple, acellular organization and
pattern of reproduction. A complete virus particle or virion
consists of one or more molecules of DNA or RNA enclosed in a coat of
protein, and sometimes also in other layers. These additional layers may be very
complex and contain carbohydrates, lipids, and additional proteins.

Viruses can exist in two phases: extracellular and intracellular. Virions, the
extracellular phase, possess few if any enzymes and cannot reproduce independent
of living cells. In the intracellular phase, viruses exist primarily as replicating nucleic
acids that induce host metabolism to synthesize virion components; eventually
complete virus particles or virions are released. Because they are unable to
reproduce independent of living cells, viruses cannot be cultured in the same way
as bacteria and eukaryotic microorganisms.