The virus appears to have originated in Wuhan, a Chinese city about 650 miles south of Beijing that has a population of more than 11 million people. The Huanan Seafood Wholesale Market, which sells fish, as well as a panoply of meat from other animals, including bats, snakes and pangolins, was implicated in the spread in early January.
Prestigious medical journal The Lancet published an extensive summary of the clinical features of patients infected with the disease stretching back to Dec. 1, 2019. The very first patient identified had not been exposed to the market, suggesting the virus may have originated elsewhere and been transported to the market, where it was able to thrive or jump from human to animal and back again. Chinese authorities shut down the market on Jan. 1.
On Feb. 22, a report by the Global Times, a Chinese state media publication, suggested the Huanan seafood market was not the birthplace of the disease citing a Chinese study published on an open-access server in China.
Markets have been implicated in the origin and spread of viral diseases in past epidemics, including SARS and MERS. A large majority of the people so far confirmed to have come down with the new coronavirus had been to the Huanan Seafood marketplace in recent weeks. The market appears to be an integral piece of the puzzle, but research into the likely origin and connecting a "patient zero" to the initial spread is ongoing.
An early report, published in the Journal of Medical Virology on Jan. 22, suggested snakes were the most probable wildlife animal reservoir for SARS-CoV-2, but the work was soundly refuted by two further studies just a day later, on Jan. 23. "We haven't seen evidence ample enough to suggest a snake reservoir for Wuhan coronavirus," said Peter Daszak, president of nonprofit EcoHealth Alliance, which researches the links between human and animal health.
"This work is really interesting, but when we compare the genetic sequence of this new virus with all other known coronaviruses, all of its closest relatives have origins in mammals, specifically bats. Therefore, without further details on the testing of animals in the markets, it looks like we are no closer to knowing this virus' natural reservoir."
Another group of Chinese scientists uploaded a paper to preprint website biorXiv, having studied the viral genetic code and compared it to the previous SARS coronavirus and other bat coronaviruses. They discovered the genetic similarities run deep: The virus shares 80% of its genes with the previous SARS virus and 96% of its genes with bat coronaviruses. Importantly, the study also demonstrated the virus can get into and hijack cells the same way SARS did.
The ant-eating pangolin, a small, scaly mammal, has also been implicated in the spread of SARS-CoV-2. According to the New York Times, it may be one of the most trafficked animals in the world and it was sold at the Huanan Seafood Market. The virus likely originated in bats but may have been able to hide out in the pangolin, before spreading from that animal to humans. Researchers caution the full data have not yet been published but coronaviruses similar to SARS-CoV-2 have been found in pangolins before.
All good science builds off previous discoveries -- and there is still more to learn about the basic biology of SARS-CoV-2 before we have a good grasp of exactly which animal vector is responsible for transmission -- but early indications are the virus is similar to those seen in bats and likely originated from them.
<
h2 style="background-color: white; font-family: "Proxima Nova", sans-serif; font-size: calc(2.29885vw + 0.45977px); line-height: 1.07em; margin: 15px 0px; text-rendering: optimizelegibility;">
How many confirmed cases/deaths have been reported?
The virus has spread to over 50 countries since its discovery in late 2019 and the number of cases and deaths have been steadily rising since early January. The best way to keep track of the spread of the virus across the globe is this handy online tool, which is collating data from a number of sources including the CDC, the WHO and Chinese health professionals and is maintained by Johns Hopkins University.
The bulk of the confirmed cases and deaths have been recorded in China's Hubei province where the outbreak originated. However, secondary outbreaks have been seen in South Korea, Italy and Iran and a cruise ship, the Diamond Princess, was quarantined in the Japanese port of Yokohama for 14 days in February due to an outbreak onboard. In total, 705 people on the ship were found to be infected with the coronavirus.
0 Comments