The novel coronavirus that causes COVID-19 is likely to have originated in wild animals in China rather than in a laboratory, according to the World Health Organization.

“All available evidence suggests the virus has an animal origin and is not manipulated or constructed in a lab or somewhere else,” Reuters cited Fadela Chaib, a spokeswoman for the WHO, as saying at a Tuesday news briefing. “It is probable, likely, that the virus is of animal origin.”

Last week, U.S. President Donald Trump said “there is a lot of investigation going on” into whether the novel coronavirus may have come from a laboratory in Wuhan, the central Chinese city where the virus was first detected, adding that such a theory “seems to make sense.”

However, international public health authorities — including Dr. Anthony Fauci, one of the U.S.’s top infectious disease experts — have rejected this possible origin story as a fringe theory supported by little or no evidence.

On Monday, China’s foreign ministry responded to Trump’s remarks, calling them subjective and lacking in scientific evidence. Spokesman Geng Shuang added that where the coronavirus comes from is a scientific question and should not be politicalized.

The origin of SARS-CoV-2 has been hotly debated in the months since the outbreak was first reported in China. In particular, the Wuhan Institute of Virology — a research institute under the Chinese Academy of Sciences that houses the country’s only Biosafety Level 4 lab for studying highly infectious diseases — has been accused of leaking the virus, possibly through staff selling test animals at Wuhan’s South China Seafood Wholesale Market to make some extra cash.

Netizens and fringe news sites have pointed to a 2015 paper by Shi Zhengli, a coronavirus specialist at the institute, that details how Shi and her team isolated a new coronavirus found in native populations of horseshoe bats, as apparent evidence for their claims.

Shortly after the rumors surfaced in early February, Shi dismissed them as the work of “conspiracy theorists who don’t believe in science” in an interview with financial outlet Caixin. “I swear on my life that this has nothing to do with our laboratory,” she posted on her personal account on social app WeChat. On Saturday, the BSL4 lab’s director, Yuan Zhiming, also said there was “absolutely no way” the COVID-19 virus could have originated at the institute.

Nevertheless, the great origin debate has raged on in the online sphere. In mid-March, a famous Chinese vlogger was bullied by nationalist netizens for apologizing on behalf of her country after the virus had begun to spread around the globe. Her critics argued that she had nothing to be sorry for, as the origin of the coronavirus had not been confirmed. Meanwhile, fake news and disinformation about the COVID-19 pandemic and its possible origin in the U.S have been widely shared on WeChat and Weibo — China’s dominant social media platforms — to the point that content moderators have been spurred to action.

Though the source of SARS-CoV-2 has not yet been confirmed, many scientists believe the virus came to humans from bats — the presumptive reservoir host — via an as-yet-unknown intermediate host that may have been handled and sold at the South China Seafood Wholesale Market, where many of the first cases were traced. To reduce the risk of further animal-to-human diseases, China in late January announced a blanket ban on the domestic wildlife trade.

Last week, President Trump said that the U.S. — by far the world’s largest donor to the WHO — would defund the global health body while “a review is conducted to assess the World Health Organization’s role in severely mismanaging and covering up the spread of the coronavirus.” His remarks prompted swift criticism from China and the international community, with foreign ministry spokesman Zhao Lijian urging the U.S. to “fulfill its responsibilities and obligations” to support the WHO.

Editor: David Paulk.

(Header image: A colorized scanning electron micrograph of cells (red) infected with SARS-CoV-2 viruses (yellow), isolated from a patient’s sample. Image captured at the Integrated Research Facility of the National Institute of Allergy and Infectious Diseases in Fort Detrick, Maryland, U.S. NIAID)