The coronavirus first surfaced in the world from the industrial and transportation hub on the Yangtze River. It’s also possible that the virus came to Wuhan undetected from some other place, but the city of 11 million is a logical place to kick off the mission.

People began falling ill in December 2019, many with links to a sprawling food market that popular for dealing with live animals. The growing number of patients triggered alarms that obliged China’s Center for Disease Control and Prevention to send a team to investigate.

The disease ravaged Wuhan before it was brought under control in March. The city was locked down on Jan. 23 with little or no warning. The severe suffering and privation endured by the residents became a source of both sorrow and pride for residents once the 76-day lockdown was lifted on April 8.

First, they have to quarantine for 14 days, during which they will work with Chinese counterparts via video conference. After their quarantine duration is over, they will most probably be visiting are the Huanan Seafood Market, the site of the December 2019 cluster of cases, and the Wuhan Institute of Virology after that.

Scientists had initially suspected that the virus came from wild animals sold in the market. The market has since been largely ruled out, it could still provide hints on how the virus spread so widely. Samples from the market are still available, along with the testimony of those involved in the early response.

The Wuhan Institute of Virology maintains an extensive archive of genetic sequences of bat coronaviruses built in the wake of the 2003 SARS pandemic, which spread from China to many countries. WHO team members are hoping to get access to lab logbooks and data, both junior and senior researchers, and safety protocols for sample collection, storage, and analysis.

China has decisively rejected calls for an independent outside investigation. The head of the WHO recently expressed impatience with how long China took to make required arrangements for the team’s visit.

The ruling Communist Party firmly holds information and is particularly concerned about possible revelations about its handling of the virus that could open it up to international criticism and financial demands.

China only gave fragmented reports about the outbreak and has published very little information on its search for the origins of the virus. An investigation discovered that the government has strictly controlled all scientific research related to the outbreak and forbids researchers from releasing them to the press.

State media continues to play up reports that suggest the virus could have originated somewhere else. While addressing the experts’ visit, Foreign Ministry spokesperson Zhao Lijian said “the tracing of the virus origin will most likely involve multiple countries and localities.”