The Hong Kong Medical Association has warned there is a high risk of a dengue fever outbreak this summer. The disease first swept through Hong Kong last year and is now regarded as endemic. Association spokesman Dr So Man-kit said the average ovitrap index, also known as the 'mosquito index', showed that the risk this year was high. 'According to the Singapore experience, if the index is close to 2 per cent, it is sufficient for epidemic transmission. So far the index in Hong Kong has been higher than 2 per cent,'' Dr So said. He said 20 people contracted dengue fever during last year's outbreak, proving that mosquitoes in Hong Kong were carrying the virus. Kenneth Lee Kwing-chin, professor of the Chinese University's school of pharmacy, warned that people infected with dengue fever should not take aspirin or the Cox-2 inhibitor, both of which are commonly used to cure fever. He said aspirin could cause internal bleeding and permanent organ damage in dengue fever patients. It is particularly dangerous for children, pregnant women and the elderly. Dr Lo Wing-lok, who represents the medical sector in the Legislative Council, urged the public to help keep the environment clean to stop dengue fever. 'We should make it a habit to clean up our living environment and ensure we get rid of stagnant water,' he said.