ABOUT VIRUSES AND COVID -19

SRI KRISHNA INSTITUTE(IAS/PCS COACHING)

Viruses: Important factual information and COVID 19

" They live at the edge of life"( called as replicators)

"They don't reproduce, they just make their copies using the machinery of the host cell"

Viruses are submicroscopic infectious agents, which can replicate or make copies inside the living cell called as host cells.

Dmitri ivanovsky(1892) described them as non-bacterial pathogens and Martinus beijerinck discovered TMV(tobacco mosaic virus) in 1898.

"OUTSIDE A CELL THEY EXIST AS INDEPENDENT PARTICLES CALLED VIRIONS"

STRUCTURE:

They have a very simple structure

a) Protein coat or capsid
b) A strand of genetic material , which can be either DNA/RNA (never both)
c) In some viruses there exists and outside envelop of lipids/fats.

VIROME:

A COMPLETE SET OF VIRUSES IN AN ORGANISM OR HABITAT.

e.g.:- All human viruses contribute to human virome.

Study of viruses is called as Virology, an advanced branch of Microbiology.

VIRULANCE:

It is a pathogen's or microbe's capacity to infect or damage host or it is relative ability of a virus to cause diseases.

ZOONOTIC DISEASES: 

It is an infectious disease caused by a pathogen that has jumped or came from non-human animals.

e.g. Ebola-Bats
Rabies-Dogs, Cats,Wolves
Bird flu-Birds
Swine flu-Pigs
Covid-19-Bats(presumably)

VIRUSES AS VECTORS:

In genetics scientists often use viruses as vectors i.e. to transfer specific genes in to target cells and develop required characters or traits in the host cell. (vectors-which carry genes from outside to inside of host cell. They can be compared to vehicles on which genes can travel inside a host cell)

VIROTHERAPY:

It is a branch of science , which uses viruses to treat certain diseases . Viruses have been used in treatment of cancer and can also be used in Gene therapy( A therapy developed to introduce required genes in a cell for treating abnormal genes and make required beneficial substance like a protein or hormone inside the host cell). 

HUMAN DISEASES: ( ONLY RECENTLY IN NEWS)

1.AIDS-HIV VIRUS( RNA  VIRUS)
2.CHICKENPOX-VERICELLA ZOSTER VIRUS(DNA VIRUS)
3.COMMON COLD-RHINOVIRUSES(RNA VIRUS)
4.RABIES-RABIES VIRUS(RNA VIRUS)
5.EBOLA-EBOLA VIRUSES(RNA VIRUS)
6.AVIAN INFLUENZA(BIRD FLU)-H5N1 VIRUS(RNA VIRUS)
7.SARS(SEVERE ACUTE RESPIRATORY SYNDROME)-SARS CoV 1 VIRUS( RNA VIRUS)
8.SPANISH FLU(1918-BLACK DEATH PANDEMIC) -H1N1 INFLUENZA STRAIN(RNA VIRUS)
9. SWINE FLU(2009)-INFLUENZA C, H1N1,H1N2 AND OTHER STRAINS OF INFLUENZA -A VIRUSES(RNA VIRUS)
10. COVID -19(RECENT PANDEMIC) -SARS CoV 2/ nCoV-2019( NOVEL CORONA VIRUS)-(RNA VIRUS)

* STRAIN MEANS  A VARIETY OF VIRUS.
* H5N1-H MEANS HEMAGGLUTININ AND N MEANS NEURAMINIDASE ( These are small protein spikes on the viral surface that help to invade cells)
* HEPATITIS B  AND C ARE ALSO VIRAL DISEASES CAUSED BY RNA VIRUSES.

COVID-19

Corona virus disease 2019 caused by SARS-CoV 2 VIRUS OR nCoV 2019(Novel corona virus.
It is a single stranded RNA virus, which is also called as WUHAN virus or WUHAN coronavirus.

First strains were discovered in WUHAN province of CHINA.

Name SARS-CoV 2  has been chosen because this virus resembles genetically to coronavirus responsible for 2003 outbreak of SARS.

Disease caused by the virus is COVID-2019.

NOTE: Name CORONA has been chosen because in LATIN CORONA means CROWN. Virus spike peplomers look like corona. Peplomers are glycoprotein spikes  on virus capsid which help to invade host cell.( Red colored spikes visible on corona virus surface pictures available online.)

No vaccine has been created for this pandemic disease so far.

It is highly contagious disease which spreads through droplets coming out of an infected person's mouth or nose during coughing and sneezing.

Usual onset of symptoms is 5 days from exposure , ranging between 2-14 days.

NOTE:

DIAGNOSTICS METHOD is rRT-PCR i.e. Reverse transcription polymerase chain reaction from a nasopahryngeal swab( a swab taken from back of the nose and throat.

ARUN JOSHI