The average ovitrap index for August rose to 13.7% from 12.8% in July, and readings in six areas reached or exceeded the alert level of 20%, the Food & Environmental Hygiene Department says.

The six areas are Ma On Shan (25.5%), Wong Tai Sin Central (25.4%), Tung Chung (25%), Kwun Tong Central (24.1%), Tuen Mun North (23.7%) and Fanling (20%).

Of the 38 areas surveyed last month, all recorded positive ovitrap indices ranging from 3.6% to 25.5%. The figure for port areas dropped to 0.6% from 1% in July.

The ovitrap indices reflect the prevalence of Aedes albopictus, a mosquito that can transmit Dengue fever.