A mystery viral respiratory outbreak in China is not SARS, MERS or bird flu, authorities have said.

Healthcare workers in the Wuhan region are still working to identify the virus, its cause and the source, but do not yet have answers.

The mystery pneumonia, which emerged last month, has so far infected 44 people in China and 15 in Hong Kong.

Seven of those unwell in China are said to be in a critical condition, while the rest are stable.

Singapore has said it will screen people for any infection when they arrive on flights from China.


There had been fears the virus could be severe acute respiratory syndrome (SARS), which killed more than 700 people and terrified hundreds of thousands in 2002-03.

In Hong Kong, doctors have been ordered to report cases of fever in anyone who may have travelled to Wuhan in the past fortnight, and hospitals have been put on high alert.

A total of 59 people have been diagnosed with the mysterious condition in Wuhan and have been isolated while they receive treatment, according to the city's municipal health commission.

Doctors are also observing 121 people with whom the patients had been in close contact.

The commission said in a statement that initial investigations have ruled out SARS as well as Middle East respiratory syndrome (MERS), influenza, bird flu and adenovirus.

Image: Workers disinfect the waiting room of a Beijing railway station during the SARS outbreak in 2003

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

Several patients were working at the South China Seafood City food market in sprawling Wuhan's suburbs.

City officials said a clean up at the market has been completed, and that no obvious human-to-human transmission had been seen and no medical staff had been infected.

Hong Kong's Hospital Authority said Sunday that a total of 15 patients in Hong Kong were being treated for symptoms including fever and respiratory infection after recent visits to Wuhan.

Hospitals and doctors have been directed to report cases of fever in anyone who has travelled to Wuhan in the past 14 days, Hong Kong's health chief Sophia Chan added.

The hospital authority said it has activated a "serious response" level to curb spread of the infection.

Ms Chan warned Hong Kong residents against visiting wet markets and eating wild game in mainland China.

The World Health Organisation (WHO) said it was closely monitoring the situation and maintaining contact with Chinese authorities.

It has said no travel or trade restrictions are necessary at this time.

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

He added that there are several potential causes of viral pneumonia, many of which are more common than SARS.