Coronaviruses are a large family of viruses known to cause diseases ranging from the common cold to more serious diseases such as the Middle East Respiratory Syndrome (MERS) and the Severe Acute Respiratory Syndrome (SARS).

They are positive-stranded RNA viruses with a crown-like appearance under the electron microscope. The subfamily Orthocoronavirinae of the family Coronaviridae is further classified into four coronavirus (CoV) genera: Alpha-, Beta-, Delta- and Gammacoronavirus. The Betacoronavirus genus is further divided into five subgenera (including the Sarbecovirus)

Coronaviruses were identified in the mid-1960s and are known to infect humans and a variety of animals (including birds and mammals). Epithelial cells in the respiratory and gastrointestinal tract are the primary target cells.

To date, seven coronaviruses have been shown to infect humans:

• Common human coronaviruses: HCoV-OC43 and HCoV-HKU1 (Betacoronavirus) and HCoV-229E and HCoV-NL63 (Alphacoronavirus); they can cause common colds but also severe lower respiratory tract infections.
• other human Coronaviruses (Betacoronavirus): SARS-CoV, MERS-CoV and 2019-nCoV (now named SARS-CoV-2)

A novel coronavirus (nCoV) is a new strain of coronavirus never previously identified in humans. In particular, the virus named SARS-CoV-2 (formerly 2019-nCoV), was never identified before it was reported in Wuhan, China, in December 2019.

The virus that is causing the current coronavirus outbreak has been named ‘severe acute respiratory syndrome coronavirus 2’ (SARS-CoV-2). This designation was communicated by the International Committee on Taxonomy of Viruses (ICTV), virus taxa (i.e. species, genus, family, etc.). The name was given by a group of experts specially appointed to study the novel coronavirus. According to this pool of scientists, the novel coronavirus is a sister to severe acute respiratory syndrome coronaviruses (SARS-CoVs); this is why it has been named SARS-CoV-2.

The disease caused by the novel Coronavirus has been named ‘COVID-19’ (where "CO" stands for corona, "VI" for virus, "D" for disease and "19" indicates the year in which it occurred). This was announced on 11 February 2020 by the Director-General of the WHO, Dr Tedros Adhanom Ghebreyesus.

No. The novel Coronavirus (now named SARS-CoV-2, formerly labelled 2019-nCoV) belongs to the same family of viruses as the Acute Severe Respiratory Syndrome (SARS) virus, but it is not the same virus.

The novel Coronavirus, which is responsible for the respiratory disease now named COVID-19, is closely related to the SARS-CoV and is genetically classified in the genus Betacoronavirus, subgenus Sarbecovirus.

The appearance of new viruses that originally only infected animals but then make the jump from animal to humans is a well-known phenomenon (‘spillover’), and this is what seems to have happened with the new coronavirus (SARS-CoV-2). Currently, the scientific community is trying to identify the source of the infection.

To date, the source of SARS-CoV-2, the coronavirus that causes COVID-19, is unknown. Available evidence suggests that SARS-CoV-2 is of animal origin and is not a constructed virus. Most likely the ecological reservoir of SARS-CoV-2 resides in bats. SARS-CoV-2 belongs to a group of genetically related viruses, including SARS-CoV (the coronavirus causing SARS) and a number of other coronaviruses isolated from bat populations.