VIROLOGY

Virology is a branch of science that deals with the detailed study of viruses. Virologist is a person who studies the viruses. Virologist explores the structure of virus, components that are present in the virus, how virus evolutes, virus exploitation and disorders they induce. They isolate the culture of virus and research them in laboratory. Virology is referred as part of microbiology, a science that deals with microorganism study and pathology, science that deals with pathogens.

Structure

Viruses are very smaller in size. Their size varies from 30nm to 450nm. Virus cannot be seen through light microscope. It requires electron microscope, X-ray crystallograph and Non-magnetic resonance microscope.

Classification

Broad application of virology study is to predict their structure and classification.

• Based on host cell infection
  • Plant virus
  • Animal virus
  • Fungal virus
  • Bacteriophage
• Based on shape
  • Capsid ( Helical or icosahedron)
  • Viral structure (Envelope presence or absence)
• Based on nucleic acid presence
  • DNA virus (Double stranded virus)
  • RNA virus (Single stranded virus)
  • Retrovirus (may be double stranded or single stranded)
• Sub-viral particles
  • Viriods (naked RNA)
  • Prions (proteins found in pathological substantiation)
  • Satellites ( Genetic material either with capsid or not, require virus called helper virus for infecting the host)

Hypothesis of Virus evolutionary relationship

Evolution of virus is not clear, hence virologists proposed three hypotheses.

• Viruses are formed from non-living matter.when some other living matters are produced
• They may arise from parasitic forms depending on the host cells.
• Transport of genetic materials namely through plasmids and transposons

Viral diseases

The need for virus study is mainly because of disorders it causes. Following are viral disease caused by different types of viruses. Viral pathology is a branch of science that deals with study of disease caused by virus.

• Common cold
• Rabies
• Diarrhea
• Polio
• AIDS/HIV
• Influenza
• Yellow fever
• Hepatitis
• Cancer
• Small pox

Host defence mechanism against viral infection

The mechanism by which a host can fight against the virus infection are listed below

• Production of antibody, especially monoclonal antibody
• Cell mediated immunity
• RNA interference
• Antiviral drugs