Before March 2020, many people saw pandemics as a thing of the past. Then came COVID-19. Scientists still do not know exactly where the virus that caused it — SARS-CoV-2 — came from, but it soon reached almost every country worldwide. Over 2 years, the virus has evolved, producing several variants. In this Special Feature, we look at the evolution of SARS-CoV-2 and ask what lessons scientists have learned.
What have we learned in 2 years of COVID-19? Image credit: Dia Dipasupil/Getty Images.
In late 2019, there was a sudden increaseTrusted Source in pneumonia cases in central China. By January 7, scientists had identified and isolated a previously unknown coronavirus, now designated SARS-CoV-2.
On March 11, 2020, the World Health Organization (WHO)Trusted Source declared COVID-19 a pandemic.Now, 2 years on, authorities have recorded more than 458 million cases of COVID-19, the disease resulting from SARS-CoV-2. The disease has also played a role in the deaths of more than 6 million people.
Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment. However, the actual death toll may well be far higher than 6 million. According to a recent paper in The LancetTrusted Source, the actual death toll may be at least three times that.
On December 29, 2019, experts linkedTrusted Source four cases of pneumonia of unknown etiologyTrusted Source to the Huanan Seafood Wholesale Market in Wuhan, central China.
On January 7, 2020, researchers isolated the causative agent, SARS-CoV-2, and on January 10, they sequenced its genome.
By January 2, 2020, doctors had confirmed that 41 peopleTrusted Source in a Wuhan hospital with severe respiratory illness had a SARS-CoV-2 infection. Of these individuals, 27 had had exposure to the seafood market. Many coronaviruses exist, affecting both animals and people. Most cause infections with mild to moderate symptoms in the upper respiratory tract, such as colds.
In recent years, two coronaviruses — SARS-CoV and MERS-CoVTrusted Source — have caused more severe disease.
