The battle against mosquitoes is being stepped up in Hong Kong after a sharp rise in the number of cases of dengue fever spread by the insects. Five cases were notified in 1996 and 10 last year, but by the end of July this year, eight had already been identified. An annual campaign against the insects is starting three months early in an attempt to stop the disease spreading. A survey has pinpointed Tsuen Wan as a high-risk zone with large numbers of mosquitoes in the area.