(Yicai Global) Jan. 2 -- An investigation into the cause of an outbreak of pneumonia in Wuhan, the capital of China's central Hubei province, has so far shown that the contagion was not passed from person to person, according to the local health authority, which added that no medical staff have been infected.

Twenty-seven people, mostly vendors at the Huanan Seafood Wholesale Market in Wuhan, fell ill with a mysterious pneumonia on Dec. 30, the city government said at the time. Health experts identified the illness as viral pneumonia, officials said a day later. In response, the government immediately closed and sterilized the market.

"It is surprising that pneumonia broke out at a wholesale seafood market," a virologist told Yicai Global. "Though there are viruses present in seafood, they aren't normally passed on to humans."

Law enforcement officials found that the market was also selling wild animals such as edible frogs, snakes and hedgehogs, according to a September statement from the local market watchdog. Wuhan is also rich in wetlands -- some 1,562 square kilometers -- which makes up 18.4 percent of the city's total area. Expansive waters and a lot of vegetation attract large numbers of migratory birds in winter. One of China's three main bird migration routes passes through Wuhan.

Hubei has various subtypes of avian influenza viruses in the natural environment given the province's AIV epidemic situation, and genetic recombination or gene mutation may happen because of frequent gene exchanges among these viruses, the virologist added.

During preliminary examinations doctors at local hospitals are now asking patients whether they have been to the Huanan Seafood Wholesale Market, a number of these patients told Yicai Global. Chest x-rays have been added to the check list besides blood test and patients are also asked to undergo computerized tomography scans if they are diagnosed with pulmonary infection.

Editors: Xu Wei, Chen Juan, Peter Thomas