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Updated: Feb 22, 2020 20:37 IST

The novel coronavirus (covid-19) could have begun transmission between humans in November from a place other than the seafood market in Wuhan in Hubei province, new research by institutes under the Chinese Academy of Sciences (CAS) has said.

Until now the Huanan seafood market in the outbreak epicentre Wuhan has been seen as the most probable location where the virus had jumped from a wild animal to a human in December, and then quickly spread across China and beyond.

The new study contradicts that sequence of events – and pushes back the timeline of the outbreak significantly.

It says that the coronavirus was introduced to the seafood market from another location – by a human – and then rapidly spread in the city.

The findings were the result of analyses of genome data, sources of infection and the route of spread of 93 samples of the novel coronavirus collected from 12 countries across four continents including the US, France, Australia, Japan, and Taiwan.

“The new coronavirus from the South China seafood market was introduced from other places, and spread rapidly outside the market; at the same time, the current spread of cases came from at least 3 routes. The new coronavirus had two significant population expansions before February 12 (December 8 and January 6 respectively),” the study said.

“According to the new coronavirus genome data, it was estimated that the population expansion before January occurred on December 8. This result suggests that the virus may have spread from person to person in early December and even in late November, and then accelerated human-to-human transmission in the south China seafood market,” the study added.

The authors argued that a “patient zero” could have passed on the virus to workers or sellers at the Huanan seafood market; subsequently, the crowded market facilitated the further transmission of the virus to buyers, which could have then triggered a wider spread in early December 2019.

“Researchers further confirmed that infection cases in the other nine provinces and 11 other countries in China were basically directly or indirectly imported from Wuhan,” the study said.

The study estimates that the population expansion before February was January 6, which was related to the annual travel rush related to the Chinese New Year’s day holidays.

“It should be noted that on this day, the National Centre for Disease Control and Prevention issued a Level 2 emergency response. Early warnings at that time served as a warning, and public activity and travel were reduced. If the warnings at that time could (have) attracted wider attention, the number of cases spreading nationally and globally in mid-to-late January would (have) been reduced,” the study said.