Satish Pillai, Medical Officer in the Division of Preparedness and Emerging Infections at the Centers for Disease Control and Prevention, talks during a press conference in Shoreline, Washington on Tuesday, January 21. Jason Redmond/AFP/Getty Images

Advisers to the US Centers for Disease Control and Prevention (CDC) told CNN they are concerned that Chinese health officials have still not released basic epidemiological data about the Wuhan coronavirus outbreak, making it more difficult to contain the outbreak.

We're more than three weeks into the outbreak, with more than 600 infections and at least 17 people dead. Yet it’s still unknown how many patients got sick via contact with infected animals at the market where the virus first emerged versus how many patients got sick through person-to-person contact.

Other unknowns include the amount of time from exposure to the virus to the onset of symptoms, or at what point after infection someone becomes contagious.

Dr. William Schaffner, a professor at Vanderbilt University Medical Center and longtime CDC adviser, said if this outbreak were in the US, these questions would likely be answered by now – and those answers would help disease detectives put a stop to the outbreak sooner.