With the onset of warmer weather, the government's alert system for dengue fever is starting to buzz. It shows that Ma Wan Island, where the first local outbreak of the disease was recorded last July, is still Hong Kong's hot spot. Since January, the government has been monitoring the distribution of the Aedes albopictus mosquito, a carrier of dengue fever, in select areas through what it calls an 'ovitrap index'. The measure was introduced after the first local outbreak was detected among workers at the Park Island development on Ma Wan. Twenty people came down with dengue fever from July to September last year. The index jumped from 1.4 per cent in March to 11.4 per cent last month. This is consistent with seasonal patterns but lower than the 30.2 recorded at the same time last year. But eight areas recorded readings of more than 20 last month, including the highest of 39.3 at Ma Wan. Wong Tai Sin Central was next at 37.5, followed by Cheung Chau 36.4, Lowu 26.1, Kwai Chung 22.6, Tung Chung 22.2, Kennedy Town 22 and Tai Po North at 21.7. Officials called for greater public awareness. 'We are under constant threat [of dengue fever], so it is important that everybody make an effort to reduce the mosquito population,' environmental hygiene consultant Ho Yuk-yin said. Officials also spoke about the need to remain vigilant against other diseases such as bird flu. Microbiology expert and council chairman Yuen Kwok-yung said: 'Control of avian flu in our locality and in China is important for the world.'' He said Hong Kong's vaccination of chickens would help prevent the re-assortment of genes between the H5 and human influenza virus.