A new genetic analysis of the virus that causes Covid-19 taken from more than 7,600 patients around the world shows it has been circulating in people since late last year, and must have spread extremely quickly after the first infection.
Researchers in Britain looked at mutations in the virus and found evidence of quick spread, but no evidence the virus is becoming more easily transmitted or more likely to cause serious disease.
“The virus is changing, but this in itself does not mean it’s getting worse,” genetics researcher Francois Balloux of the University College London Genetics Institute told CNN.
Balloux and colleagues pulled viral sequences from a giant global database that scientists around the world are using to share data. They looked at samples taken at different times and from different places, and said they indicate that the virus first started infecting people at the end of last year.
“This rules out any scenario that assumes SARSCoV-2 may have been in circulation long before it was identified, and hence have already infected large proportions of the population,” Balloux’s team wrote in their report, published in the journal Infection, Genetics and Evolution.
That is one piece of bad news. Some doctors had hoped the virus was circulating for many months and may have quietly infected many more people than has been reported. That would offer the hope that there might be some immunity already built up in some populations.
“Everyone was hoping for that. I was too,” Balloux said.