A homeless person walks among tents on Skid Row in Los Angeles, California on Saturday. Photo: AFP

The early launch of research into the "fastest ever vaccine" by the US as revealed by President Donald Trump sheds light on the virus timeline and chain of events in the US that arouses global suspicions about the true source of the virus. 

Trump said that scientists at the US National Institutes of Health began developing the first vaccine candidate on January 11, while on January 12 Beijing time, China first shared the genome sequence information of the new coronavirus with the World Health Organization.

January 11 is one or two months earlier than the February-March initial reported outbreak in the US and 10 days earlier than the first confirmed coronavirus case reported in the US on January 21. 

The US deliberately concealed its knowledge of the impending epidemic even as China reported the unknown pneumonia to the world on January 3, Yang Zhanqiu, deputy director of the pathogen biology department at Wuhan University, told the Global Times Sunday. 

"Unless the US had patients contracted with the coronavirus beforehand or had strains of the virus in hand, there was no possibility that within hours of the virus genetic code being posted online that the US had already started vaccine candidate development," Yang said. 

The timeline revealed US attempts to scapegoat China and divert attention from its own failures to combat the virus, said Li Haidong, a professor at the institute of international relations at the China Foreign Affairs University in Beijing.

Chinese and American internet users commented online that the US owed the world an explanation after Trump's vaccine announcement.

Evidence has been growing that the worldwide pandemic likely had spread to the US or Europe weeks or possibly months before January. 

Two patients in Snohomish county, Washington state had coronavirus symptoms in Christmas last year and later tested positive for the deadly virus, the Seattle Times reported on May 14. 

"The US probably had coronavirus in December, but was too busy watching China to notice," ran a headline in Business Insider on May 12. 

The US president was warned of the pandemic as early as January according to timelines published on March 31 in US media.

In testimony to the US Congress in March, Robert Redfield, director of the Centers for Diseases Control and Prevention (CDC), said it was possible some COVID-19 deaths last year were diagnosed as flu-related in the US.