Investigation into Fort Detrick is the call of all the people around the world, including the Chinese, which must be answered by the United States in terms of tracing the origin of the coronavirus, a foreign ministry spokesperson said July 21.

Spokesperson Zhao Lijian made the remarks at a daily press briefing, as a joint open letter calling on the World Health Organization (WHO) to investigate the Fort Detrick lab has gained about 5 million signatures from Chinese netizens as of July 21 afternoon.

The open letter has been well received by the Chinese, with around 5 million people signing in less than five days, showing their indignation over some U.S. people's political manipulation using the issue of origin-tracing.

"The mystery of Fort Detrick remains unsolved," he said.

In July 2019, the U.S. Centers for Disease Control and Prevention sent a letter to Fort Detrick, asking it to terminate most operations. In the same month, respiratory diseases of unknown origin began to appear in northern Virginia, and a large-scale EVALI broke out in Wisconsin. At the end of July, a respiratory disease which could cause pneumonia for unknown reasons appeared in two nursing homes near Fort Detrick, and in September, Maryland, where Fort Detrick is located, reported that the number of patients with EVALI had doubled, according to Zhao.

Even so, the United States refused to disclose the reasons for closing Fort Detrick on the grounds of "national security", he said.

Noting that Fort Detrick still stores a large number of viruses that seriously threaten human lives, as reported by U.S. media, Zhao asked when the United States would publicly clarify the issue.

The United States should show transparency, take concrete measures to thoroughly investigate the origin of the epidemic in the country, find out reasons for poor COVID-19 response and hold accountable those who are responsible, thoroughly investigate Fort Detrick as well as more than 200 overseas biological experimental bases, and give an explanation to the people around the world and to the international community, he said.