Conflicting studies on source of coronavirus divide scientists
The mysterious source of the novel coronavirus outbreak, which originated in Wuhan, central China and since spread globally, has led to a significant divide among scientists worldwide.
While a team of scientists has raised doubts that the virus originated from Wuhan's Huanan Seafood Market, another group of researchers claims snakes sold in the market led to the outbreak. These conflicting findings has led to heated debate among researchers.
Finding the source of the outbreak is crucial to preventing and controlling future outbreaks of the virus. The origin of the novel coronavirus is still unknown, but it's most likely an animal reservoir, said the World Health Organization (WHO).
Theory 1: The seafood market may not be the source
A comprehensive study led by a team of more than 20 Chinese researchers analyzed data from 41 patients diagnosed with the new virus, known by its technical name 2019-nCoV, at a hospital in Wuhan.
They found only 27 out of 41, or 66 percent of patients, had direct exposure to Huanan Seafood Market. The rest of the admitted patients had no exposure to the market.
Since the first case of the virus was identified on December 1 and admitted to the hospital, "none of his family members developed fever or any respiratory symptoms," said researchers.
"No epidemiological link was found between the first patient and later cases," researchers wrote in the study published in the Lancet journal.
The Wuhan government suspects the source of the outbreak was the market and closed it down on January 1. A range of animals and pre-packaged meat on sale were removed in order to control the virus from spreading.
Theory 2: Snakes as the intermediary host
But another research team led by researchers from Peking University claims snakes – Chinese krait and the Chinese cobra – sold along with other wild animals at the Huanan Seafood Market, were a possible host of the new coronavirus.
They analyzed the protein codes favored by the new coronavirus and compared it to the protein codes from coronaviruses found in different animal hosts, like birds, snakes, marmots, hedgehogs, bats and humans.
The coronavirus family also causes severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), usually found in bats, requires an intermediary host – palm civets in the case of SARS and camels for MERS – to infect humans.
"Snakes were also sold at the Huanan Seafood Wholesale Market where many patients worked or had a history of exposure to wildlife or farm animals," said the study accepted for publication in the Journal of Medical Virology.
"Taken together, [bats] and snakes could be the most probable wildlife animal reservoir for the 2019-nCoV."
The study concluded that snakes were an intermediary host of the virus jumping on to humans, which has killed 107 and infected more than 4,400 people as of January 28.
But a growing number of researchers worldwide feel that the snake theory lacks credibility.
The "entire research paper doesn't make any sense."It's true bats are reservoirs of coronavirus, but an intermediary host is likely to spread the virus among humans at the beginning of the outbreak." In this case, snakes are the unlikely hosts," Dr. Xiaowei Jiang, at Xi'an Jiaotong-Liverpool University (XJTLU), told CGTN.
"We are still unsure about the animal from which the new strain of virus transferred to humans," said David Robertson of the University of Glasgow's Center for Virus Research.
Citing major flaws in the study, a section of virologists and epidemiologists, have also urged the journal to retract the paper.
"There could easily be other species out there that are more similar than snakes, but we don't know because they just haven't been put in the analysis," Edward Holmes, a zoologist at the University of Sydney told Wired.
Theory 3: Evidence washed away
With the local government cleaning out the seafood market, chances of identifying the intermediary host of the outbreak are bleak.
Unless a large team of scientists are deployed to collect the DNA samples from the market, it is impossible to find the source, said Xiaowei.
"The incident calls for governments to formulate a policy for this type of clean-up that is generally led by municipality officials with little knowledge about sample collection," he added.
The WHO, concerned over the issue, maintained that specific investigations to understand the source of the novel coronavirus, notably the animal reservoir, and animals involved in the zoonotic transmission is needed to control the outbreak.
Most of these outbreaks happen in remote areas where the focus of local officials remains on cleaning the suspected place from where the virus originated. "These officials have limited knowledge of sample collection to ascertain the source of the outbreak. Thus major clues are lost," researchers said.
The inclusion of scientists and researchers before making the clean-up plan would help in finding the source of the outbreak. "It would also help in containing the outbreak and quality research," suggested Xiaowei.
(Cover Image: Huahan Seafood Market has been cleaned up to control the intensity of the outbreak. /CCTV Photo)