(Yicai Global) Dec. 6 -- Fifteen years after the outbreak of Severe Acute Respiratory Syndrome (SARS), Chinese scientists have found all the genetic pieces of the SARS virus in a single population of horseshoe bats, the 'Nature Research' account on China's popular WeChat messaging app reported.
To find the origin of the deadly SARS virus, the researchers conducted a nationwide study and finally found the smoking gun in a remote cave in Yunnan province in southwestern China.
Virologists discovered a population of horseshoe bats in whose bodies they found all the genetic pieces of the SARS virus that spread to human beings and caused around 800 deaths worldwide in 2003.
The SARS virus likely came from this bat population. These genetic pieces may once again result in the outbreak of a similar disease, the researchers warned in their report titled 'Public Library of Science (PLOS) Pathogens.'
Cases of a pneumonia-like illness started emerging in Southeast China's Guangdong province in late 2002. The disease, called Severe Acute Respiratory Syndrome (SARS), triggered a global emergency as it spread around the world the following year, infecting thousands of people.
Scientists identified the culprit as being a strain of coronavirus and found genetically-similar viruses in masked palm civets sold in a Guangdong livestock and poultry market. The ensuing survey showed many SARS-related coronaviruses widespread in Chinese horseshoe bats, suggesting that the deadly strain probably originated in these flying mammals and spread to human beings via the civet cats. However, crucial genes differed in the human and the bat strains of the virus, which cast doubt on the hypothesis.
To solve this 'cold case,' Shi Zhengli and Cui Jie, researchers of Wuhan Institute of Virology (WIV), sampled many horseshoe bats all over the country. After finding a human-like coronavirus strain in a cave in Yunnan, the researchers monitored bats in it for up to five years.
They analyzed a genetic sequence of 15 strains from the bats, learning that they collectively had all the genetic pieces which go to make up the human version of the virus. Although no single bat had the exact strain of SARS coronavirus afflicting humans, analysis indicated that these variants frequently mixed. Kwok-Yung Yuen, a virologist at the University of Hong Kong who jointly discovered the SARS virus, said that the human type might originate from this restructuring. "The author of the report confirmed the previous suspicion, and this warrants congratulation," he said.
Tu Changchun, Director of the OIE Reference Laboratories for Rabies in China, believes the research result is only "99 percent" persuasive, however. He would like to see scientists demonstrate in the lab that the human SARS strain can spread from bats to other animals, such as civets. "If they can prove it, then the evidence will be perfect," he said
Another unsettled question is how a virus in bats in Yunnan could spread to animals and humans around 1,000 kilometers away in Guangdong, without any suspected cases arising in Yunnan. "This issue has puzzled me for a long time," Tu said.