A coronavirus patient contracted the killer virus in just 15 seconds after standing near to an infected person.
Medics are now carefully tracking the 14-day history of the 56-year-old man.
The patient had had no previous contact with animals and was not acquainted with any confirmed carriers of the virus.
A report by the Jiangbei Health Commission said the man named only as “Patient 5” stood next to a confirmed female carrier - 61-year-old “patient 2” - at a booth inside Shuangdongfang market on January 23
And the death toll has now surpassed 500 amid ongoing fears the Chinese government are not admitting the full extent of the outbreak.
The report noted that at 7.47am local time, patient 5 came in brief contact with patient 2 for just 15 seconds while neither was wearing a surgical mask.
The same morning, patient 5 then went on to visit two more supermarkets and finally a restaurant before he was diagnosed with the pneumonia-like Wuhan coronavirus on February 5.
Jiangbei health officials said 19 individuals who had close contact with the five confirmed coronavirus patients - among 18 carriers in the city of Ningbo - have since been put in quarantine.
The number of isolated individuals stood at 92 as of 5th February, the commission said.
The Wuhan coronavirus strain has killed 563 people in mainland China and two others in Asia.
There are more than 28,200 confirmed cases worldwide – including in Britain and the US.
Coronavirus is a SARS-like virus which can incubate for two weeks before striking down a person with fever and a dry cough.
Reports have emerged claiming crematoriums in the epicentre of the outbreak Wuhan are working 24/7 to deal with the bodies.
Chinese authorities are now threatening anyone who reports “unofficial” news about the coronavirus with seven years in jail.
Meanwhile, the World Health Organisation has issued a global appeal for £520 million in donations as it seeks to combat the spread of coronavirus.
The preparedness and response plan has been launched by the WHO, which is requesting the sum in order to support countries with weaker health systems.
Director-General Dr Tedros Adhanom Ghebreyesus said "urgent support" was needed to help countries detect, diagnose and care for people with the virus to prevent further human to human transmission.
It is understood that the British Government is currently considering its contribution, while the Irish Government pledged half a million euros (£425,000) to the WHO, who is spearheading the international response.
Also in China, the Global Times newspaper reported that a newborn baby in Wuhan has been diagnosed with coronavirus.
It has lead medical experts to suggest the virus can somehow be transmitted between mother and baby.
In Japan, nearly 3,000 passengers, including two Britons, were quarantined on board a cruise ship after 10 passengers tested positive for coronavirus on Wednesday morning local time.
The ship is being quarantined for 14 days and there are no plans to fly people back home.
The Department of Health said on Wednesday that 468 people in the UK have now tested negative for coronavirus.
Of almost 1,500 people who arrived on direct flights from Wuhan in January, all have either left the UK or are now outside the 14-day incubation period for the virus.
The WHO said it is still early in the outbreak, but coronavirus does not yet constitute a pandemic.
It comes after the Foreign Office urged all British nationals to leave China on Tuesday, after the outbreak continued to claim lives.
Health Secretary Matt Hancock chaired a Cobra meeting on coronavirus on Wednesday afternoon, after saying the Government is "taking no chances" with British citizens at risk.
He told the BBC that the advice to leave was a "science-led approach" based on the severity of the virus and its impact in China.
Hospitals have been told to create "priority assessment pods" for patients with suspected coronavirus in efforts to prevent them mixing with other patients.
According to letter from Professor Keith Willett, NHS strategic incident director for coronavirus, the pods are expected to be up and running no later than Friday.
On Tuesday evening, eight British nationals and their dependants left the virus-hit city of Wuhan on a flight to Auckland, New Zealand.