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Investigators looking into the COVID-19 mystery could be one step closer to unmasking "patient zero."

A seafood merchant in Wuhan, China, is believed to be the first person diagnosed as having the coronavirus, which can be linked back to a wet market in China, leaked documents allege.

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The Daily Mail reported Thursday that China's The Paper claims Wei Guixian, a 57-year-old woman working in Wuhan is the first person on record to be infected with the coronavirus.

Wei told the media outlet she started feeling sick on December 10. Thinking she might have the flu, she went to a local clinic seeking treatment. She was given some pills and then got back to work, selling live shrimp at the market.

Fast forward a week and Wei was barely conscious and clinging to life in a Chinese hospital bed.

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Two months after Wei went to the doctor, entire countries around the world had been put on lockdown. Industry ground to a halt and financial markets went into free-fall. On Thursday, the number of people infected with COVID-19 around the world surpassed the 500,000 mark.

Since the beginning, doctors have struggled to connect the dots between Wei and other early cases of coronavirus, The Daily Mail reported. When they were able to establish a link between Wei and 24 out of 27 of the earliest patients on record, officials quarantined her. But by then, the damage had already been done. Wei and others were also forbidden by Chinese authorities to warn their peers or the public about the monster virus taking over their bodies.

Wei told China's The Paper that in the beginning she thought she had a simple case of influenza - something she got every year.

"I felt a bit tired, but not as tired as previous years," she said. "Every winter, I always suffer from the flu. So I thought it was the flu."

After going to a local clinic where she was given some pills, Wei continued to sell seafood at the market while she sick.

Her symptoms didn't get any better. In fact, they got worse. A lot worse.

Wei then took herself to a second medical center.

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"The doctor at The Eleventh hospital could not figure out what was wrong with me and gave me pills," she said. "But then I felt a lot worse and very uncomfortable. I did not have enough strength or energy."

On Dec. 16, she checked in at the city's largest hospital, the Wuhan Union Hospital. It was there that doctors told her she had a "ruthless" illness and that several others from the area seemed to also have.

Wei, unlike many people who have gotten the coronavirus, survived.

And though she is not patient zero, she is the first person to test positive for COVID-19 in the Wuhan market thought to be the epicenter of the crisis.

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The first known coronavirus patient is reported to be a bed-bound man in his 70s with no connection to the seafood market where Wei worked.

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However, investigators believe patient zero is not the septuagenarian who had the disease on Nov. 17.

They fear patient zero could have been mingling with the public weeks earlier.