Leading British researchers analyzed over 7,000 SARS-CoV-2 genome sequences to trace the virus's early spread. Their findings suggest patient zero was likely infected between October 6 and December 11, 2019—making this the most comprehensive analysis to date.
Officially, SARS-CoV-2 first surfaced at a market in Wuhan, China, in December 2019. Yet, the exact emergence date remains debated, with ongoing research refining estimates. Recently, a University of Cambridge team proposed an even earlier origin in September 2019, in an area south of Wuhan, based on 1,001 complete genome sequences.
Building on this, experts from University College London published a study on May 5, 2020, in Infection, Genetics and Evolution. They examined 7,710 genome sequence assemblies collected globally since January 2020, estimating patient zero's emergence between October 6 and December 11, 2019.
Despite mutations and evolutionary changes, the team identified the most recent common ancestor (MRCA), providing a robust new timeline for the COVID-19 pandemic's start.
These estimates align with prior research using smaller genomic datasets and varied methods, though all findings warrant cautious interpretation.
The researchers also highlight the virus's adaptation to humans: 198 genomic sites showed independent recurrent mutations, with 80% altering proteins. Notably, four sites mutated independently more than 15 times.
