BEIJING, April 29, 2009 (AFP) - Pork seller Yuan Zhufeng fears for her livelihood after a sudden drop in customers at one of Beijing's big markets, with people unsure over whether they can contract swine flu from eating meat.

"People have decided not to buy pork because of this swine flu," said the 47-year-old butcher at Dongjiao Market, located in the heart of Beijing where residents still remember the panic caused by the SARS epidemic in 2003.

"I can't shift my meat and I'm worried that our business is going to get worse, Yuan said, adding she and other pork sellers had already started to drop their prices.

The flu virus has since swept across parts of the globe, with confirmed cases in the United States, Costa Rica, Europe, Israel, and New Zealand.

China has not yet reported any cases, but has mobilised the nation's health system to tackle a potential crisis, mindful of fears caused by recent bird flu outbreaks that similarly saw people shun poultry.

The concern comes amid deep confusion in China and the rest of the world over how the virus transmits and where it originated.

Chinese authorities have highlighted that eating well-cooked pork poses no threat to health.

"At present there is no evidence suggesting that swine flu can be transmitted through food products, so eating properly handled cooked pork and pork products is safe," the health ministry said Sunday in a statement.

But at the same time, the Chinese government has banned imports of pork from flu-hit Mexico and parts of the United States.

The confusion was obvious at the market in Beijing, where Ma Zhen, a 25-year-old photographer carrying a bag full of shrimps, said he was staying away from pork.

"After hearing the news, I'm not willing to buy pork - it's quite a serious illness, and I know there's none in China yet but there could be," he said.

In Shanghai, concerns over swine flu also saw some customers shunning pork.

In a market in the northeast of the city, Lillian Wu, a 28-year-old customer, said she was choosing fish over pork despite believing catching the disease was not linked to eating the meat.

"I am still worried after reading so many reports on how deadly the flu could be," she said.

"I might give up eating pork temporarily, and try some other alternatives like chicken, beef or fish."

China, with the world's largest pig population at close to 450 million, is potentially at high risk from an outbreak of the deadly strain of flu.

But adding to the confusion, global health bodies have voiced uncertainty over how the virus transmits and whether it was even caught from pigs in the first place.

According to Joseph Domenech, chief veterinary officer at the UN Food and Agriculture Organisation, the new virus is composed of a mix of genes that come from pigs, poultry and humans.

"The human cases that were reported in Mexico and the United States did not come into contact with pigs," he told AFP over the phone from Rome.

'so we are unfortunately still wondering where this virus came from, and where this new recomposition (of different genes) took place - in the human being, the pig, or even in poultry."