The recent resurgence of novel coronavirus infections in Beijing might date back to a month earlier, according to China's CDC head.

Gao Fu, director-general of the Chinese Center for Disease Control and Prevention, said at a conference in Shanghai on Monday that the new cases in Beijing might not occur in late May or early June, because many viruses have been found in the environment of the Xinfadi market, which was caused by large number of asymptomatic cases and cases with mild symptoms there.

The novel coronavirus can survive in a dark and humid environment for a long time and suddenly cause new infections, which "is something we hadn't considered before", he said.

But he cautioned that it is only speculation and further confirmation is needed to determine when new infections start.