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article imageWhy it is critical that we find the source of the coronavirus

By Karen Graham     Jan 26, 2020 in Science
Scientists say it is critical they find out whether most coronavirus cases have been caused by a repeated spillover of the virus from animals to humans, or whether most cases are now being triggered by secondary human-to-human transmission.
On January 26, China's health commission minister, Ma Xiaowei warned that the coronavirus’s ability to spread appeared to be getting stronger reports The Guardian.
“The transmissibility shows signs of increasing and the ‘walking source of infection’ (where patients appear to be asymptomatic) has made it difficult to control and prevent the disease,” said Ma Xiaowei.
“For this new coronavirus we have not identified the source of the infection and we are not clear about the risk of its mutation and how it spreads. Since this is a new coronavirus there might be some changes in the coming days and weeks, and the danger it poses to people of different ages is also changing.”
This latest warning comes about as the death toll from the outbreak has risen to 56, while authorities say almost 2,000 have been infected. The mayor of Wuhan said he expects another 1,000 new cases in the city. The US, France, and Japan said they were arranging evacuation flights for people trapped in Wuhan, which has been placed under quarantine.
Health authorities in China believe the epicenter of the coronavirus outbreak, officially called 2019 novel coronavirus (2019-nCoV), is a seafood market in Wuhan, where wildlife was sold illegally.
The SARS-like coronavirus first emerged in the central Chinese city of Wuhan  where a seafood market...
The SARS-like coronavirus first emerged in the central Chinese city of Wuhan, where a seafood market has been identified as the centre of the outbreak
STR, AFP/File
Tracing the source of the virus matters
Efforts to understand the 2019-nCOV outbreak are especially crucial for a number of reasons. And while it is important for scientists to understand how it spreads, it is also critical to find out if this outbreak is still caused mainly by animals. If so, it can be controlled.
However, if new cases are now being triggered by human-to-human transmission, the chances that a major global epidemic is now underway will be raised dramatically reports The Guardian.
“That would be the big epidemiological goal for everyone at the moment,” Trevor Bedford, an evolutionary geneticist at Fred Hutchinson Cancer Research Center in Seattle, Washington, told the journal Nature.
“What’s critical to understand is whether that’s occurring at a rate and with a level of efficiency which would sustain a human epidemic,” says Neil Ferguson, a mathematical epidemiologist at Imperial College London. By monitoring the rate at which new cases appear, and when symptoms begin, it is possible to figure out how easily the virus can pass between humans.
Coronavirus
Coronavirus
Gal ROMA, AFP
Tracking the animal source
Viruses in animal hosts tend to invade a certain type of animal cell without harming people. Take for example the avian flu virus - it gets into the intestines and respiratory tracts of birds. Occasionally, according to CBC Canada, the virus will jump the species barrier, infecting humans.
"We're always on the lookout for the strange ones like SARS," says Dr. Scott Weese, a veterinary professor at the University of Guelph who is interested in novel coronaviruses from the perspective of emerging and infectious diseases. Dr. Weese notes that in the SARS outbreak, civet cats and raccoon dogs were found to carry and spread the virus, as well as domestic cats and ferrets.
"We always worry about bats as the original source, but what made it go from a bat to a person? Is there an animal in between and is that something we need to be paying attention to, or is it just human-to-human transmission?"
So far, geneticists have found out that the genetic sequences of the various strains of 2019-nCoV isolated in patients are remarkably similar to each other. What does this mean? The lack of diversity suggests a common ancestor. However, the rapid expansion of the virus has yet to be determined.
SARS killed 349 people in mainland China and another 299 in Hong Kong in 2003
SARS killed 349 people in mainland China and another 299 in Hong Kong in 2003
, AFP/File
The big question is this - Did the expansion take place in humans, or did it need an additional animal reservoir to take place? “We need to gain a better understanding of what’s going on in China,” said Prof Jonathan Ball, of Nottingham University. “In particular, how the virus is being spread, whether individuals with mild or no symptoms can transmit the virus, and, of course, where the virus came from in the first place.”
It will be necessary to test the animals from the Wuhan market, or containers and cages, for viral genetic material, says Ben Cowling, an epidemiologist at the University of Hong Kong. doing so will help to identify any genetic changes or mutations that might have helped the virus make the jump from animals to humans.
And more importantly, as the outbreak continues to drag on - scientists will be looking for signs that the virus has gained further mutations enabling it to spread more efficiently in humans.
More about coronavirus, animal to human, human to human, Transmission, animal host
 
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