BEIJING, May 15 (Xinhua) -- China had carried out research about the novel coronavirus at the fastest possible speed under existing conditions at the early stage of its anti-epidemic work and has been unreserved in sharing information, a Chinese official said Friday.

Zeng Yixin, deputy head of the National Health Commission, made the remarks at a press conference in response to a question regarding the time interval between the reports of the earliest cases in the country and the official announcement of the human-to-human transmission of the virus.

Zeng said the novel coronavirus disease is a completely new one threat to humanity and China did not make a premature announcement of its transmissibility because its knowledge about the virus was still "on the way" at the time and yet to be sufficient to draw a conclusion.

"Theoretically speaking, all viruses and bacteria can be transmitted from people to people."

However, the scientists and experts needed to find out the sources of infection, how contagious the virus is and how it is transmitted, which varies a lot among different viruses, he explained.

The official cited examples of diseases such as hepatitis B and HIV/AIDS, which are also infectious but have relatively limited transmissibility compared with COVID-19.

With very limited clinical cases at that time, Chinese experts and health workers spared no time in conducting relevant investigations and research, so as to find out the answers to support the decision-making in a scientific manner, he added.

From the very beginning of the disease, China has been adhering to a people-centered approach, making scientific policies for anti-epidemic work, and has been unreserved in sharing relevant information with the world, he said.