The pathogen SARS-COV-2

COVID-19 disease is caused by a virus of the coronavirus family, SARS-CoV-2, in the order of nidovirales. Like SARS-COV-1, SARS-CoV-2 belongs to the betacoronavirus genus and sarbecovirus sub-genus [3].

To date, there are seven different types of human coronaviruses, four of which cause mild to moderate respiratory diseases, such as common colds. The other three cause more severe and occasionally fatal diseases. These are:

• SARS-CoV-1, responsible for the severe acute respiratory syndrome (SARS);
• MERS-CoV, responsible for the Middle East respiratory syndrome (MERS); and
• SARS-CoV-2, responsible for COVID-19.

Like all viruses, SARS-CoV-2 evolves and adapts itself through mutation. While most emerging mutations have no significant impact on the spread of the virus, some mutations or combinations of mutations provide the virus with a selective advantage, e.g. increased transmissibility or the ability to evade the host immune response. In such cases, these mutations or combinations of mutations (also called variations) can increase the risk to human health, and the virus strains (or variants) that carry those mutations are classified as variants of concern (VOCs) [4].

ECDC continuously assesses new evidence on the emergence and circulation of VOCs in the EU and reports its findings on the evolution of SARS-COV-2.