Nearly 50 people contract mystery respiratory illness in China

Scores of people have now contracted a mystery respiratory illness linked to a food market in China, local health authorities said.

At least 44 people have now been infected in the outbreak of a new type of viral pneumonia, awakening memories of the 2003 ​Sars outbreak that killed nearly 800 people.

Wuhan city health commission said while 11 of the cases diagnosed since December were listed as critical, all those afflicted were being treated in isolation and 121 people who had been in close contact with them were under observation.

The most common symptom is fever, with shortness of breath and lung infections appearing in a "small number" of cases, the commission said.

The World Health Organisation said it was aware of the reports, is monitoring the situation and is in contact with the Chinese government.

"Investigations are still being carried out and authorities cannot yet confirm what pathogen is causing this illness," said WHO spokesperson Tarik Jasarevic.

Early laboratory tests indicated the disease had not been transmitted from human to human, the officials said.

Authorities have sought to quash fears the outbreak marks a re-emergence of Severe Acute Respiratory Syndrome (Sars), which took hundreds of lives, virtually shut down travel to China and took a severe toll on the economy before it was brought under control using quarantines and other extreme measures.

While the cause of the new illness remains unknown, the commission said it has ruled out known respiratory diseases. This includes avian influenza, occasional outbreaks of which have appeared among those working with live poultry.

Most cases have been traced to the South China Seafood City food market in Wuhan. The commission said an investigation and clean-up effort were underway at the food market.

In Hong Kong, the Hospital Authority said two female patients who had recently travelled to Wuhan had been admitted to hospital and were being treated in isolation for fever and respiratory infections or pneumonia symptoms. The patients, aged 12 and 41, were listed in stable condition.

The authority said neither had been to South China Seafood City and it was not clear if there was a direct connection to those patients in Wuhan.

Five patients have been admitted to hospital in Hong Kong since December with similar symptoms, two of whom have been discharged, the authority said.

At the onset of the Sars epidemic, Chinese authorities covered up the outbreak for weeks before a growing death toll and rumours forced the government to openly admit to the disease's spread, apologise and vow full openness in future outbreaks.

Additional reporting by agencies