|
Virus an ultramicroscopic infectious agent that reproduces
only in living cells; usually considered as lying in the borderline between
the living and the non-living world made up of a protein coat (capsid)
inside which the genetic material, DNA or RNA, is housed. Because the
virus cannot multiply except when inside another living cell, it can be
called a perpetual parasite. There are bacterial viruses, the bacteriophage,
which grow in bacteria. Then there are plant viruses and animal viruses.
Some common viral diseases of man are: AIDS, yellow fever, dengue fever,
poliomyelitis, hepatitis, rabies, influenza, mumps, measles, pox, herpes,
rotavirus diarrhoea, Chron's disease, and a variety of encephalitis. Several
types of cancers are believed to be caused by a class of virus called
oncogenic virus. Many plant viruses cause disease in agriculturally important
plants such as rice, tobacco, tomato, potato, cauliflower, and many fruits.
[Zia Uddin Ahmed] |
