Write an essay (at least 250 words ) about Covid-19.

Coronaviruses cause disease in mammals, including humans and birds. In humans, viruses that cause respiratory infections are usually mild but in rare cases can be fatal. Coronavirus usually causes symptoms of the common cold, an infection of the nose, sinuses, or throat, and is spread through sneezing and coughing. However, it can lead to more serious respiratory illnesses such as severe acute respiratory syndrome (SARS) and death. The pneumonia epidemic began in mid-December 2019 in the city of Wuhan, central China, when a group of people became ill with pneumonia of unknown cause, mainly related to traders working at the Hai Market. Hoa Nam products, the market specializes in selling live wild animals. Chinese scientists then found a previously unknown strain of coronavirus, which was provisionally designated 2019-nCoV by the WHO and then officially named SARS-CoV-2 by the Commission. International Taxonomy of Viruses (ICTV). This newly discovered coronavirus has a genome that is at least 70% similar to the virus that caused the 2003 SARS epidemic.