ABOUT CORONA VIRUS

Fig: Schematic diagram of SARS-CoV-2

Corona virus is scientifically known as Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It is the strain of coronavirus that causes coronavirus disease 2019 (COVID-19). SARS-CoV-2 is a positive-sense single-stranded RNA virus and is the successor to SARS-CoV-1, the strain that caused the 2002–2004 SARS outbreak.

Each SARS-CoV-2 virion is 50–200 nanometres in diameter.Like other coronaviruses, SARS-CoV-2 has four structural proteins, known as the S (spike), E (envelope), M (membrane), and N (nucleocapsid) proteins; the N protein holds the RNA genome, and the S, E, and M proteins together create the viral envelope. The spike protein, which has been imaged at the atomic level using cryogenic electron microscopy, is the protein responsible for allowing the virus to attach to and fuse with the membrane of a host cell; specifically, its S1 subunit catalyzes attachment, the S2 subunit fusion.Like other coronaviruses, SARS-CoV-2 particles are spherical and have proteins called spikes protruding from their surface. These spikes latch onto human cells, then undergo a structural change that allows the viral membrane to fuse with the cell membrane. The viral genes can then enter the host cell to be copied, producing more viruses. Recent work shows that, like the virus that caused the 2002 SARS outbreak, SARS-CoV-2 spikes bind to receptors on the human cell surface called angiotensin-converting enzyme 2 (ACE2). The researchers found that the SARS-CoV-2 spike was 10 to 20 times more likely to bind ACE2 on human cells than the spike from the SARS virus from 2002. This may enable SARS-CoV-2 to spread more easily from person to person than the earlier virus.

Despite similarities in sequence and structure between the spikes of the two viruses, three different antibodies against the 2002 SARS virus could not successfully bind to the SARS-CoV-2 spike protein. This suggests that potential vaccine and antibody-based treatment strategies will need to be unique to the new virus. The researchers are currently working on vaccine candidates targeting the SARS-CoV-2 spike protein. They also hope to use the spike protein to isolate antibodies from people who have recovered from infection by the new coronavirus. If produced in large quantities, such antibodies could potentially be used to treat new infections before a vaccine is available.

TRANSMISSION

Fig: An Artistic representation of infectious droplets dispersing in the air after sneezing.

COVID-19 spreads primarily when people are in close contact and one person inhales small droplets produced by an infected person (Could be asymptomatic) coughing, sneezing, talking, or shouting. This is the reason why it is recommended by doctors and governments to follow social distancing norms (i.e maintaining a minimum distance of 1.5 meters).

People can transmit the virus without showing symptoms, but it is unclear how often this happens. People are most infectious when they show symptoms (even mild or non-specific symptoms), but may be infectious for up to two days before symptoms appear (pre-symptomatic transmission). They remain infectious an estimated seven to twelve days in moderate cases and an average of two weeks in severe cases.

When the contaminated droplets fall to floors or surfaces they can, though less commonly, remain infectious if people touch contaminated surfaces and then their eyes, nose, mouth or other parts with mucous membranes with unwashed hands. On surfaces the amount of active virus decreases over time until it can no longer cause infection, and surfaces are thought not to be the main way the virus spreads.

Surfaces are easily decontaminated with household disinfectants which kill the virus outside the human body or on the hands.Disinfectants or bleach are not a treatment for COVID‑19, and cause health problems when not used properly, such as when used inside the human body. One of the best methods of decontamination is direct exposure of sunlight on the infected surface for a period of at least  20 minutes.

Sputum and saliva carry large amounts of virus. Although COVID‑19 is not a sexually transmitted infection, kissing, intimate contact, and faecal-oral routes are suspected to transmit the virus. Some medical procedures are aerosol-generating,and result in the virus being transmitted more easily than normal.

Fig: Respiratory droplets produced when a man sneeze ( source: Wikipedia)

What is COVID-19?

Fig:A Healthcare Worker in PPE

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It was first identified in December 2019 in Wuhan, Hubei, China, and has resulted in an ongoing pandemic.              

 

 

Other names by which it is referred are:

Coronavirus

Corona

COVID

2019-nCoV acute respiratory disease

Sars-Cov

Novel coronavirus pneumonia

Severe pneumonia with novel pathogens