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MELBOURNE (BLOOMBERG) – The best minds in virology are trying to unravel a mystery: How did a lethal coronavirus leap from the jungle of rural China to the main centers of human population? And what chain of genetic mutations produced a pathogen so perfectly suited for stealth and mass transmission?
Deciphering the story of the creation of Sars-CoV-2, as the virus that is now sweeping across the world is known, is a crucial step in stopping a pandemic that killed more than 270,000 and triggered what could be the worst collapse economic since the Great Depression.
While crash vaccine programs are underway in the United States, Europe, and China, an inoculation to avoid the virus may not be ready for months, and the jury is out of potential treatments.
Meanwhile, to reduce the risk of secondary fatal outbreaks or the emergence of an entirely new strain, disease hunters need to retrace the pathogen’s journey around the world. That means returning to China, where it was first detected in 2019.
Last week, the World Health Organization asked Beijing for permission to send a new scientific mission for more epidemiological detective work. China, which allowed a WHO team to enter the country in early February due to the epidemic, has yet to sign.
President Xi Jinping, who personally oversees the response of the China virus and the investigation into how the outbreak started, maintains tight control over Chinese scientific research, which must be approved before publication by authorities, according to two people familiar with the situation.
However, as death toll and unemployment rise worldwide, pressure on Beijing is mounting to allow international researchers to re-interview survivors, do fieldwork, and examine virus samples that the country has been petty about sharing, according to the United States.
Almost half a year after a historic global health crisis, there are still huge gaps in our knowledge. Those unanswered questions are hampering our ability to contain the outbreak and prevent future pandemics, while fueling a war of words between the United States and China over the origins of the virus.
Approximately 70 percent of emerging infectious diseases in humans are zoonotic or transmitted from animals to people. Sars-CoV-2 genome sequencing shows that it is related to two other deadly coronaviruses that originated in bats.
The severe acute respiratory syndrome, which started in China in 2002, and the Middle East respiratory syndrome a decade later spread to humans through a secondary animal source. In the case of Sars, experts pointed to civet cats (small, elegant nocturnal mammals used in wildlife dishes in China) as the likely conduit. With Mers, camels are believed to be the carriers.
Sars-CoV-2 is presumed to have made a similar journey, but researchers have yet to identify an intermediate animal host, according to Peter Ben Embarek, a food safety and animal disease expert at the WHO.
“We have some kind of missing link in that story between the origin of the virus and when it started circulating in humans,” he said.
Domestic animals
That raises the disturbing possibility that an unknown animal source is still spreading the disease, known as Covid-19. WHO researchers reported on Friday (May 8) that domestic cats can transmit the virus to other cats, although there is still no evidence that pets can transmit it to humans.
On the way to a new scientific mission to learn more about the origins of the virus in China, there are practical issues of conducting impartial investigations into an authoritarian political system and a geopolitical rivalry between the United States and China that has become especially unpleasant lately.
The Trump administration accused Beijing of a massive cover-up on the severity of its epidemic. He claimed, without providing evidence, that an accidental leak of the virus could have occurred at a bio-research laboratory in Wuhan, the central Chinese city where the outbreak was first identified. A Chinese official, in a tweet, accused the US military of introducing the pathogen into the country.
Scientists who have studied the genetics of the virus are convinced that it is of natural origin rather than designed in a laboratory.
Theoretically, an accidental release from the research center in Wuhan is possible, but “it is highly unlikely,” according to Stanley Perlman, a professor of microbiology and immunology at the University of Iowa, who has visited the facility and highly rated it.
One reason is the reputation of Dr. Shi Zhengli, 56-year-old deputy director of the Wuhan Institute of Virology.
In 2004, Dr. Shi found a natural coronavirus reservoir in bat caves near Kunming, a city in the southern Chinese province of Yunnan. In February, he published an article in the journal Nature that said the genomic sequence of the new pathogen was 96% identical to that of a coronavirus identified in Yunnan.
Dr. Shi told Scientific American that a review of the genetic characteristics of the viruses she has worked with in the laboratory does not match those of the coronavirus that spreads in humans. In a social media post, the virologist said she would “swear on my life” that the pathogen that was causing havoc had nothing to do with her laboratory.
United States Secretary of State Michael Pompeo has rejected previous claims of “enormous evidence” that the virus escaped from a Wuhan laboratory.
That still leaves scientists wondering where and how the virus got to humans. So-called wet markets that sell live animals, such as one in Wuhan that many of the earliest cases of the disease were traced to, have previously been implicated in the spread of the disease. In this case, however, experts aren’t sure if the outbreak really started on the market or was discovered there.
Dr. Peter Daszak, a disease ecologist with the nonprofit EcoHealth Alliance, said Covid-19 likely started before the currently assumed December starting point, perhaps even outside of Wuhan. He estimates that between 1 and 7 million people each year in southern China and Southeast Asia can become infected with bat viruses. Most do not spread easily between people, and many fade away before reaching major population centers, he said.
“This particular outbreak was probably in people circulating in southern or central China in November,” or even earlier, he said.
Another scenario envisions that someone closely related to the wildlife trade will bring infected animals to the Wuhan market. Once the virus reached the burgeoning megacity of 11 million, it grew exponentially.
Another crucial question is whether the virus moved to humans directly from bats or through a secondary source. If it’s the latter, the farm or wild animal may be spreading the infection.
Pangolins, scale-covered mammals that somewhat resemble anteaters, have been suggested as a possibility, although the evidence is preliminary. If Covid-19 came directly from the bats, determining where this happened is crucial, so that authorities can institute preventive measures, such as keeping people out of the caves where flying mammals live.
Solving all of this will require a lot of scientific detective work. Viruses constantly make small mutations in their genetic material. By following a trail of genetically similar versions, disease trackers can identify the progression of the pandemic over time.
“By counting the mutations, you can reverse your virus where it all started,” said WHO animal virus expert Embarek.
Tracing the virus to its ultimate origin will also require the cooperation of the Chinese government, and a little luck. The researchers will need unrestricted access to Wuhan’s market, its wildlife sellers, patient data and animal population.
However, the price of keeping Sars-CoV-2’s origins secret would be high. If the current crisis has taught us anything, it is this: As human populations expand and invade wildlife habitats, the risk of dangerous animal viruses continues to grow. And in an interconnected world, previously localized epidemics can run around the world with blinding speed.
Without better research and surveillance systems for emerging animal viruses and regulation of traditional wildlife markets and trade worldwide, the risk of future pandemics is high.
“If we do nothing, if we continue what we have been doing for the past 50 years,” said Dr. Daszak, “there will be another.”
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