China's health authorities have been open, transparent and responsible in releasing information on COVID-19 outbreak, sharing experience and promoting international cooperation, said Wu Zunyou, chief epidemiologist at the Chinese Center for Disease Control and Prevention, in response to some countries have accused China of failing to keep the outbreak informed.

Wu said China has always been open and transparent in reporting COVID-19 outbreak, and immediately informed the World Health Organization (WHO) of the situation. The gene sequence of novel coronavirus was immediately shared with other countries in the world, and international cooperation has been strengthened in the first place.

On late December in 2019, the Wuhan Center for Disease Control and Prevention (CDC) in Central China's Hubei province detected cases of pneumonia of unknown cause.

On Dec 31, the National Health Commission and Chinese CDC sent a team of experts to Wuhan to help investigate the pandemic.

On Jan 3 in 2020, China notified WHO, US and other countries, even though it was unclear what the cause was.

At the same time, since Jan 3, 2020, China has been irregularly informing WHO and other countries of the progress of its prevention, control and research about the pandemic.

On Jan 4, head of the China CDC talked over phone with director of the US CDC about the pneumonia outbreak. The two sides have communicated on the research and prevention work.

On Jan 9, China informed the WHO about the epidemic, sharing with the WHO the initial progress in determining the cause of the viral pneumonia in Wuhan.

On Jan 12, China shared with the WHO about information on the genome sequence of the novel coronavirus.

On Jan 20-21, a WHO delegation conducted a field visit to Wuhan.

On Feb 16-24, a China-WHO joint expert team visited Beijing, Guangdong, Sichuan and Hubei's Wuhan. Two American experts were among them.

On March 12, US embassy attended a meeting during which experts from China and WHO shared experiences on the international control and prevention work.

On March 29, Chinese CDC and the US CDC exchanged views on prevention work in video meeting again.