COVID-19 (short for Corona Virus Disease that emerged in late 2019) is an infectious disease caused by a new type of coronavirus, a large family of viruses. While most coronaviruses are harmless to humans, four types cause colds, and two others—Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS)—can cause severe lung infections. The novel coronavirus was named SARS-CoV-2 because of its genetic similarities to the virus that causes SARS.
About six months into the pandemic, scientists began to detect variants of SARS-CoV-2 with mutations that make these new viruses more easily transmissible, so they spread faster and infect more people. The most concerning variants have emerged in South Africa, Brazil, and the United Kingdom, and are circulating widely within their country of origin, and increasingly in other countries. As long as the pandemic is with us—likely until the world achieves widespread global vaccination—other new variant strains, possibly also more contagious and/or more deadly, will continue to emerge.