A reconstruction of the crucial seven weeks between the appearance of the first symptoms in early December and the government’s decision to lock down the city, based on two dozen interviews with Wuhan residents, doctors and officials, on government statements and on Chinese media reports, points to decisions that delayed a concerted public health offensive.

In those weeks, the authorities silenced doctors and others for raising red flags. They played down the dangers to the public, leaving the city’s 11 million residents unaware they should protect themselves. They closed a food market where the virus was believed to have started, but didn’t broadly curb the wildlife trade.

Their reluctance to go public, in part, played to political motivations as local officials prepared for their annual congresses in January. Even as cases climbed, officials declared repeatedly that there had likely been no more infections.

By not moving aggressively to warn the public and medical professionals, public health experts say, the Chinese government lost one of its best chances to keep the disease from becoming an epidemic.