Corona - The Dreadful Virus
Now a days checking the number of Corona cases has sadly become the part of our daily routine . This few nanometer virus is impacting our life directly . So it feels really necessary to discuss everything we have understood so far about corona.
Virus are microscopic particles that consist of nucliec acid (DNA /RNA ) and a outer protein coat called capsid . The genetic material could be single stranded or double stranded . Virus are very unique in their characterstics . They are considered as connecting link between living and non living as they cannot reproduce and carry out metabolic process without a host cell . Example - Rhinovirus , HIV virus , Influenza Virus etc.
• Attachment - The viral particle attaches itself to a target host cell
• Penetration - The virus enters the target cell by receptor mediated or phagocytotic means .
• Uncoating and replication - The virus looses its envelope and the genetic material is released inside the host cell . The virus then reproduces into the host cell's nucleus .
• Assembly and release - The gentetic material are again enclosed in a capsid and viruses are released killing the host cell .
Corona viruses are single stranded RNA viruses with a capsid that causes respiratory ,intestinal , mental disease in birds and mammals . As they are spherical viruses with protein spikes projecting outwards , they give them a crowned appearance ,so they are called Corona Virus .
(Many of you might think that Corona is a single virus. But actually Corona is a group of viruses having nearly similar composition , structure and mode of infection )
The capsid contains various types of proteins -
1. Membrane proteins - helps in membrane fusion
2. Spike proteins - for attachment and entry of virus into host cells
3. Envelope proteins - for the release of viral particles from damaged cells .
4. Non-structural proteins - they suppresses the immune systeme of the host organism .
• Alpha -CoV - this viruses can infect mammals including human . Some of examples are - NL63 virus , PRCV .
• Beta-CoV - they also includes mammalian viruses like HKU4 , Mouse hepatitis virus
• Gamma-CoV - this viruses can infect both birds and mammals
• Delta -CoV - this viruses can infect birds .
As we humans are also mammals few coronaviruses are already present in nature that can infect us like 229E like virus , NL63 like virus , OC43 like virus , HKU1 like virus .
But SARS CoV , MERS CoV , SARS CoV 2 that started emerging with the start of 21st centuries become serious concerns . They are "Zoonotic Human Corona Viruses". This viruses were originally some animal viruses and due to mutation(sudden changes in genetic material ) and recombination ( pairing of non homologous chromosomes )they can now infect humans i.e. it is animal to human transmission . Emergence of three zoonotic viruses in only 17 years is dreadful and some remedy is needed seeing the future concerns .
Let's discuss this viruses one by one .
In 2002 ,Guandong ,China reported some sort of respiratory illness that was described as SARS ( Severe Acute Respiratory Syndrome ) caused by SARS CoV . It was later found that it is very similar to the beta - coronaviruses of bats . This virus emerged from bats and spreaded to humans . The symptoms included cough ( dry at first ) , diarrhoea or fever or both . The outbreak of virus was in four small waves .This virus was more fatal ( death causing ) and less contagious (spreading ) than the SARS CoV 2 .
• Mean incubation period ( time from entry of virus to appearance of symptoms ) - 5 days .
• Number of cases - 8439
• Total death - 812
• Death rate - 9.6%
In 2012 , Saudi Arabia reported a case having nearly similar virus as SARS . WHO , later recogined the disease as MERS ( Middle East Respiratory Syndrome ) . MERS CoV has its origin from camels . The men are at higher risk of catching MERS than the women . The symptoms include fever , cough and shortness of breath . The mild symptoms can lead to multiple organ failures and ultimately death .
Number of cases - 2519
Total deaths - 866
Death rates - 34 .3 %
The first case was reported in Dec ,2019 at Wuhan ,China . The virus probably originated and spread from wet market in Wuhan where seafood is being sold. Studies until now has revealed that novel coronavirus is a recombinant virus of beta -bat - coronavirus and coronavirus of some unknown source ( it may be Pangolin ) . The Novel corona virus is very contagious that in March 2020 it was declared as pandemic by WHO .
Novel corona virus uses same receptor ( Angiotensin converting enzyme 2 )as SARS to gain entry in host cell that's why it is called SARS CoV-2 .
Novel CoV causes Covid-19 ( corona virus disease in 2019 )
The symptoms includes fever , dry cough , fatigue , pnuemonia ,bronchitis , sore throat , decrease in WBCs , Platelets .
The diagnosis is done using throat swab and oral swabs .
1. Tilt the patient's head upwards
2. Insert flexible shaft mini tip through nares until resistance is met
3.Gently rub and roll the swab
4.Leave swab in place for several seconds
5.Slowly remove the swab while rotationg it and immediatly place it in sterile tube .
• Contact and droplet transmission - The disease can spread due to close contact with a person infected by Novel CoV and through infectious secretions produced during coughing , sneezing , talking , singing etc .
• Fomite transmission - The spread due to contact with the surfaces ( fomite ) that have come in contact with a pateint . It is indirect mode and will lead to community spread ( no info about source )
• Blood and serum transmission doesn't occur as studies revealed very low viral titre in blood .
Though no anticorona virus medicines and vaccine are available currently few of the drugs seems helpful
• Interferon and ribavirin - They block viral replication and mRNA maturation ( by preventing capping ) , thus preventing the multiplication of virus .
• Lopinavir and ritonavir - They affects the non structural proteins of the virus , so immune system remains completly active
• Chloroquine - It prevents the viral attachment with the host cell
• Remdesivir and favipiravir - It prevents the viral transcription ( DNA - ^ RNA ) so no new virus is produced .
All this drugs proove useful as they decrease the multiplication of virus too much extent . But we need something that ultimately kills the virus , to stop the spread . Scientists all over the globe are currently working to formulate a " vaccine " against the virus .
As the novel corona virus is spreading at a very vigorous rate , we need to break the chain of transmission . More cases would be very difficult to control .
Corona has impacted our lives in many ways even we don't know off . As it is challenging our lives today many research are going, to answer the surfacing question like Airborne transmission is possible , how much dose of virus is needed to infect , does CoVid19 can infect dogs and cats , do transmission from infected mother to baby is possible through breast feeding .. And above all " When will vaccine come " . Till then we have to stay positive ,stay calm , stay productive , stay isolated . I hope this article is useful . Thank you !!!! Do review !!