Pangolins are unlikely to have been the hosts that passed the coronavirus that causes Covid-19 on to humans, Chinese researchers said, adding that the search should focus on wild animals that share their habitats.
The endangered mammals, also known as scaly anteaters, have been identified as a possible intermediate host after a series of papers highlighted the close relationship between SARS-CoV-2, as the coronavirus is known, and similar viruses found in pangolins.
But a team led by Zhang Zhigang from Yunnan University, told Chinese publication Science Daily on Wednesday that the evidence suggested that these genetic similarities did not pass the generally accepted 99 per cent threshold needed to make the virus jump from pangolins to humans.
Researchers around the world are trying to track the way the new coronavirus infected humans and to put a stop to the pandemic, which has infected more than 400,000 people and killed more than 18,000.
Zhang said animals such as bats and pangolins were known to be natural hosts of similar viruses to SARS-CoV-2, but natural hosts normally could not pass these on to humans.
Instead, researchers needed to identify the intermediate host through which the coronavirus was transmitted.
Bats and pangolins have been the focus of attention after scientists identified them as carriers of viruses that share much of their genetic make-up with the coronavirus.
In January, a group of Chinese scientists led by Shi Zhengli, from the Wuhan Institute of Virology, found that SARS-CoV-2 shared 96 per cent of its whole-genome identity with BatCoV RaTG13, another coronavirus found on intermediate horseshoe bats (Rhinolophus affinis), which live in caves in Yunnan province.
In a research paper published last week in Current Biology, the same team found that the coronavirus carried by Malayan pangolins, named Pangolin-CoV, was the second-closest relative of SARS-CoV-2 as the two viruses were 91.02 per cent identical at the whole-genome level.
In early February, researchers from South China Agricultural University said they had found a 99 per cent similarity between the two viruses and declared the Malayan pangolin a "potential intermediate host". But they later revised their results, lowering the figure to only 90.3 per cent.
Guan Yi, a virologist from the University of Hong Kong, later also said his own research only showed 92.4 per cent similarity.
In the interview, Zhang said Shi's research had eliminated the intermediate horseshoe bat as the species that transmitted the virus to humans, but other bat species might have done so and researchers should continue to study them.
Zhang said researchers should look into the natural habitat of intermediate horseshoe bats and Malayan pangolins to find the real immediate host.
"If the horseshoe bat and Malayan pangolin can be proven to be the natural hosts, then their current natural habitat may be the place where the novel coronavirus originated," Zhang said.
"What matters now is to identify the intermediate host, where did [the jump from animal to human] happen? Why did the outbreak happen in Wuhan? These [questions] should be the main direction of future scientific research," he added.
Intermediate horseshoe bats are commonly found in South Asia, southern and central China and Southeast Asia. The Malayan pangolin (Manis javanica), also known as the Sunda or Javan pangolin, can be found throughout Southeast Asia.
For the latest updates on the coronavirus, visit here.
This article was first published in South China Morning Post.