Though the first 41 cases were reported December 31, scientists determined that the virus could have started spreading from person to person as early as late November.

Case studies of how the virus has spread showed that the large gathering of people at the live animal market may have “boosted” the transmission of the virus among more people, researchers said.

Researchers think the new coronavirus originated in bats, then jumped to an intermediary species – most likely pangolins, pigs, or civets – that passed it to people. It can be spread among humans via respiratory droplets within six feet. The viruses can also survive for days on many surfaces.

The virus’ pneumonia-like symptoms include fever and difficulty breathing.