The deadly coronavirus sweeping the globe did not begin in a Chinese fish market. Instead, researchers warn it was spreading through Wuhan for up to a month before being detected.
Known as 2019-nCoV, the virus belongs to the same family as SARS and, more recently, MERS. About 10 per cent of those infected with SARS died. The mortality rate for MERS is about 35 per cent.
How deadly 2019-nCoV? That’s yet to be determined.
And that’s why finding a ‘Patient Zero’ is so important.
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The Huanan Seafood Wholesale Market had been the primary suspect for where the new virus made its jump from the wild into humans.
But new research has found the virus must have already been in the human population.
Instead, the wild trade facility served as a “super spreader” – a concentrated hive of activity where the virus rapidly jumped to new hosts.
The Chinese government has so far remained silent about these doubts. But researchers the world over are pressing for more significant efforts to identify the earliest possible known sources of the infection.
Medical science journal The Lancet at the weekend published an update into the first known clinical reports of the virus. Chinese researchers tracked reports to 41 original cases. The earliest infections pose a serious mystery.
“No epidemiological link was found between the first patient and later cases,” they state. In fact, 13 of the first 41 had no link to the market whatsoever.
So vital questions remain:
Where did the virus come from?
How did it get into the Huanan Seafood Wholesale Market?
“Now it seems clear that the seafood market is not the only origin of the virus,” study co-author Bin Cao told the American Association for the Advancement of Science (AAAS).
“But to be honest, we still do not know where the virus came from now.”
“China must have realised the epidemic did not originate in that Wuhan Huanan seafood market,” says infectious disease specialist at Georgetown University Dr Daniel Lucey.
“The presumed rapid spread of the virus apparently for the first time from the Huanan seafood market in December did not occur,” Dr Lucy says.
“Instead the virus was already silently spreading in Wuhan, hidden amid many other patients with pneumonia at this time of year.
“The virus came into that marketplace before it came out of that marketplace”.
Initial reports identified the first patient as one diagnosed on December 8.
They also said “most” cases had an epicentre of the seafood market, and that the virus did not transmit between humans. The majority also came from one specific area of the market – that selling captured wild animals, like snakes, civet cats, beavers – and bats.
“The results suggest that the novel coronavirus outbreak is highly relevant to the trading of wild animals,” state-controlled media agency Xinhua reported.
Huanan market was closed on January 1 in a bid to slow the rate of infection.
That move now appears inadequate.
The Wuhan Municipal Health Commission had the case histories of 41 patients by January 11. The lack of contact with the market by 13 patients should have sounded alarms.
There were no further official updates for the next seven days.
The mayor of Wuhan and the Communist Party secretary responsible for the city of 11 million has since offered to resign. But only after insisting they had been unable to raise a timely warning due to strict laws about not going public until the Central Committee in Beijing agreed.
With the first diagnosis now known to have been on December 1, the virus must have been on the move in November. Its spread went unnoticed because of its apparently infectious incubation period.
But Dr Lucey says China’s new testing regimen has helped undo the damage: “Having, and rapidly deploying, the new rapid diagnostic test was a brilliant action to fight this epidemic”.
The quest for a Patient Zero is an almost impossible one.
But the closer researchers get, the greater the chance they have of understanding the disease.
It’s not like in the movies, where their blood provides a near-magical serum to cure the contagion. But it does act as a baseline from which to measure its behaviour, characteristics and mutations.
And that’s vital in assessing exactly how dangerous the virus is.
China’s health minister Ma Xiaowei has warned it already seems to be mutating, jumping from human to human much quicker than at first.
He said his country, which has taken draconian steps to control its spread, was entering a “crucial stage.”
Which brings us back to Patient Zero.
The best candidate we have so far is the person admitted to a Wuhan hospital on December 1.
“Whether this patient was infected from an animal or another person in November, directly or by fomites, his infection occurred at a location other than the Huanan seafood market,” Dr Lucey told the Science Speaks blog.
Implications are the virus had begun its march through Wuhan’s population much earlier than its appearance in the seafood market.
“Initial and potentially repeated animal-person transmission, followed by subsequent person-to-person transmission, could have begun in October-November or earlier in 2019,” Lucey says. “Patients with pneumonia due to infection with the novel coronavirus could have started to spread across Wuhan, and (through) infected travellers leaving Wuhan to other locations.”
This, along with an apparent 14-day incubation period, and an ability to infect others while a host is not displaying symptoms indicates it may have spread much further than believed.
“Despite the enormous and admirable efforts in China and around the world, we need to plan for the possibility containment of this epidemic isn’t possible,” Imperial College London infectious diseases expert Neil Ferguson told The Guardian after modelling the known characteristics of this outbreak.
Evolutionary biologist Kristian Andersen of the US-based Scripps Research Institute has analysed segments of 2019-nCoV DNA to pin down its origin.
He told the AAAS that the condition of the virus suggests a single common source from as early as October 1. This means its introduction to the market by a human source was entirely consistent with the evidence.
Bats remain the number one suspect.
They have a unique immune system which enables them to tolerate viruses. Combined with their ability to fly, this makes bats particularly effective at spreading disease.
Which is why it is no surprise that the 2019-nCoV has a 96 per cent similarity to a wild bat coronavirus.
“There’s an ever-increasing diversity of animal coronavirus species, especially in bats. So the likelihood of viral genetic recombination leading to future outbreaks is high,” writes virology investigator Professor Burtram Fielding.
“The threat of future pandemics is real as highly pathogenic coronaviruses continue to spill over from animal sources into the human population.”
Dr Lucey says he believes the original transmission of 2019-nCoV occurred elsewhere in the food supply chain. “Potentially at one or multiple places in the supply chain of the infected animals, for example in one or more multiple markets, or restaurants, or farms, or with wild animals, legal or illegal trade.”
He argues human and animal specimens collected during 2018 and 2019 must be tested for the virus or its antibodies. And all other animal markets must be put under observation to prevent retransmission from the wild.
“There might be a clear signal among the noise,” he says.
Jamie Seidel is a freelance writer | @JamieSeidel