New evidence from China confirms what epidemiologists have long suspected: The coronavirus probably started spreading unnoticed in the Wuhan area in November 2019 before exploding in December at several different locations in the city.
As of December 2019, the Chinese authorities have identified 174 confirmed Covid-19 cases in the city, World Health Organization researchers said, enough to indicate that there are far more mild, asymptomatic or otherwise unnoticed cases than previously thought.
Many of the 174 cases had no known connection to the market, which was initially considered the source of the outbreak, according to information gathered by WHO investigators during the four-week mission to China to trace the virus’ origin. to investigate. Chinese members have refused to give the WTO team raw data on these issues and potential earlier cases, team members said.
In examining 13 genetic sequences of the virus as of December, Chinese authorities found similar sequences among those linked to the market, but according to WHO researchers, slight differences in those of humans with no connection to it. The two sets probably started to differ between mid-November and early December, but could possibly indicate infections as early as September, said Marion Koopmans, a Dutch virologist in the WTO team.
This and other evidence suggests that the coronavirus may have jumped on people during or shortly before the second half of November, she said, making too few people sick to attract attention until it led to an explosive outbreak in Wuhan. By December, the virus had spread much more widely, among people who had a link with the market, as well as others who had no bond.