A mysterious respiratory illness that has infected dozens of people in a central Chinese city is not Sars, local authorities have said.

The 2002-03 epidemic of severe acute respiratory syndrome started in southern China and killed more than 700 people. Fears of a recurrence arose this month after a number of people were taken to hospital with unexplained viral pneumonia in Wuhan, the capital of Hubei province.

Fifty-nine people had been diagnosed with the condition as of Sunday. They have been isolated while they receive treatment, according to the Wuhan municipal health commission. Seven are in a critical condition.

The commission said in a statement that initial investigations had ruled out Sars as well as Middle East respiratory syndrome, influenza, bird flu and adenovirus.

The commission said previously that the condition’s most common symptom was fever, with shortness of breath and lung infections appearing in a small number of cases. There were no clear indications of human-to-human transmission.

Several patients were working at the South China Seafood City food market in Wuhan’s suburbs. The commission said the market would be suspended and investigated.

Hong Kong’s hospital authority said on Sunday that 15 patients were being treated for symptoms including fever and respiratory infection after recent visits to Wuhan.

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

The hospital authority said it has activated a serious response level to curb the spread of the infection. Chan warned Hong Kong residents against visiting wet markets and eating wild game in mainland China.

The World Health Organization said it was monitoring the situation closely and maintaining contact with Chinese authorities. No travel or trade restrictions were necessary at this time, it said.