Hong Kong's first victim of locally contracted dengue fever went to hospital in July - two months before the outbreak was made public - but doctors failed to diagnose his condition. The 36-year-old man from Ma Wan was admitted to Queen Elizabeth Hospital on July 25 and diagnosed as suffering from a viral infection. It was not until September 25 that the Department of Health traced his case to the dengue fever outbreak. Deputy director of health Leung Pak-yin disclosed yesterday that the first sufferer's symptoms had appeared on July 19. A dengue alert was only issued on September 21 when three construction workers in Ma Wan were confirmed as suffering from the fever. Dr Leung defended the surveillance system yesterday at a special meeting of the Legislative Council panel on food safety and environmental hygiene. So far 13 local cases have been confirmed, all but one of them from Ma Wan - the other being a man who said he was bitten by mosquitoes while fishing near the Cheung Sha Wan market 11 days ago. Dr Leung said he believed the outbreak was not widespread and had been limited to Ma Wan, describing the Cheung Sha Wan case as 'isolated'. About the initial case which went undetected for two months, a Department of Health spokesman said: 'The department conducted tests among the workers and residents in Ma Wan and found a Ma Wan resident who had become ill on July 19. Retrospectively, blood specimens taken during his illness were retrieved for testing on September 25.' Legislator for the medical sector Dr Lo Wing-lok said if the case had been diagnosed two months earlier, the anti-mosquito campaign could have been started sooner. 'That might have helped keep the dengue fever under control even earlier,' he said. However, he claimed that other doctors would not necessarily have been alerted to the 'rare and exceptional diagnosis' of dengue in July. A spokesman for the Hospital Authority said the man was diagnosed with a 'viral infection' and was discharged on August 2. 'At public hospitals, treatments are given to dengue fever patients according to their clinical conditions,' the spokesman said, when asked if there was any breakdown in doctors' surveillance for dengue in this case. One more imported case was confirmed yesterday, bringing to 14 the number of locals who have contracted the fever while overseas this year. Health authorities said the coming few weeks would be critical. A fact file on dengue fever can be found at the scmp.com Web site http://hongkong.scmp.com .