China's health authorities have published the latest version of the "Diagnosis and Treatment Protocol for Novel Coronavirus Pneumonia."

The updated protocol, the eighth edition, noted that the patients infected by the novel coronavirus and asymptomatic infected people are the main sources of infection.

These people are infectious in the incubation period and become more infectious within five days after onset, said the protocol.

The protocol added that exposure to virus-contaminated objects can also cause infection.

The protocol was jointly issued by the National Health Commission (NHC) and the National Administration of Traditional Chinese Medicine.

"Learning from clinical experience and optimizing diagnosis and treatment measures, we want to make the protocol more scientific, precise, and comprehensive to offer better guidance to battle the disease," said Guo Yanhong, an official with the NHC.