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Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) is an enveloped, positive-stranded RNA virus. Coronaviruses have a characteristic crown-like appearance under the electron microscope, so are named after the Latin word corona, meaning 'crown' or 'halo').

Several coronaviruses cause respiratory diseases in humans. These range from the common cold to serious diseases with high mortality rates such as Severe Acute Respiratory Syndrome (SARS), first detected in 2003, and Middle East respiratory syndrome (MERS), first detected in 2003.

All SARS-CoV-2 isolated from humans to date are closely related genetically to coronaviruses isolated from bat populations; SARS-CoV, the cause of the SARS outbreak in 2003, is also closely related to coronaviruses isolated from bats. The published genetic sequences of SARS-CoV-2 isolated from human cases are, to date, all very similar. This suggests that the start of the outbreak resulted from a single point introduction in the human population around the time that the virus was first reported in humans in Wuhan, China. 

The genome of COVID-19 is contained within the nucleocapsid which is surrounded by a envelope. The envelope is derived from the host cell's membrane and embedded within that membrane are glycoprotein spikes, known as S-proteins (surface proteins). It is these S-protein spikes that allow the cell to attach to a new cell and infect it. 

The S-proteins allow the virus particles to bind to the cell by attachment to the ACE2 receptor. S-proteins contain an S1/S2 activation cleavage site that is activated by the serine endoprotease, furin. Furin autocleavage helps the S-protein's subunits to separate and allow for the virus to infect the host cell. The ACE2 receptor is present along multiple cell organs such as the heart, kidney, lungs, and is also being found in both the central and peripheral nervous system.

The physiochemical and thermal properties of the SARS-CoV-2 virion have been determined. SARS-CoV-2 can be inactivated by UV light or at a temperature of 56°C for 30 min. Disinfectants such as diethyl ether, 75% ethanol, chlorine, peracetic acid, and chloroform can inactivate the virion. The virus has the longest viability on stainless steel and plastic surfaces and can be detected up to 72 h after initial contact to these surfaces.


Structure of SARS-CoV-2 © Roche

Structure of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2).
Source: Roche