March's monthly ovitrap index for Aedes albopictus edges up

     Despite the fact that March's monthly territory-wide ovitrap index for Aedes albopictus, a kind of mosquito which can transmit dengue fever (DF), rose slightly to 0.2 per cent from zero in February, indicating that the infestation of Aedes albopictus in the areas surveyed stayed at a low level, the Food and Environmental Hygiene Department (FEHD) today (April 27) reminded the public to keep up effective measures against mosquito breeding as Aedes albopictus will become more active with the advent of the rainy season.

     An FEHD spokesman said, "Among the 44 areas surveyed last month, positive ovitrap indices were recorded in three areas, ranging from 1.9 per cent to 3.6 per cent, with the highest being in Lam Tin. As for the port areas, the monthly ovitrap index for Aedes albopictus for March remained at zero as in February.

     "Despite the low index for Aedes albopictus recorded in March, in view of the confirmation of three local DF cases late last year and the fact that DF remained highly prevalent in neighbouring areas, and that the humid and warm weather between spring and summer is conducive to mosquito breeding, the community must remain vigilant. The Government and the public must work together in conducting anti-mosquito work. Relevant departments will continue to intensify their mosquito preventive and control work, as well as strengthen publicity and education campaigns."

     The incubation period of DF ranges from three to 14 days, commonly four to seven days. Although symptoms of first DF infection are usually mild, if the person is infected with other serotypes of dengue viruses in subsequent years, it is more likely to result in a serious complication, namely dengue haemorrhagic fever. Failing proper treatment, the fatality rate could exceed 20 per cent.

     At present, no vaccine for DF is available. Therefore, the best preventive measures are to avoid mosquito bites and adopt measures to prevent mosquito breeding.

     "To heighten public awareness of the potential risk of mosquito-borne diseases, including dengue fever and Japanese encephalitis, the second phase of this year's Anti-mosquito Campaign, which will last for 10 weeks, was launched today. During the three-phase campaign period each year, relevant government departments and public bodies will strengthen mosquito prevention and control measures as well as publicity efforts throughout the city. Besides, the FEHD will deploy additional manpower to anti-mosquito work as well as join with other relevant government departments to lay on, from May 4 to early June, two rounds of intensive mosquito preventive and control exercises across the territory covering areas under their purview. Through the two exercises, actions will be taken to kill adult mosquitoes, clear stagnant water and conduct grass cutting to eliminate potential mosquito breeding grounds so as to enhance the effectiveness of mosquito control measures," the spokesperson added.

     Aedes albopictus breeds in small water bodies. The spokesman advised the public and estate management bodies to scrub all drains and surface sewers, and to limewash them with an alkaline detergent compound at least once a week to remove any mosquito eggs.

     They should also keep drains free of blockage and fill up all depressions to prevent puddles from forming.

     "People should also inspect their homes and surroundings to remove potential breeding grounds, scrub vases and pot plant saucers at least once a week, properly dispose of containers such as soft drink cans and lunch boxes, and drill large holes in unused tyres," he said.

     The ovitrap index is divided into four levels, reflecting the infestation level of Aedes albopictus. Level 1 (< 5 per cent) indicates that infestation of the mosquito is not extensive in the area surveyed. Level 2 (5 per cent - < 20 per cent) indicates that infestation of the mosquito is slightly more extensive in the area surveyed. Level 3 (20 per cent - < 40 per cent) indicates that infestation of the mosquito exceeds one-fifth of the area surveyed. Level 4 (>/= 40 per cent) indicates that almost half of the surveyed area is infested with the mosquito. The Government will step up the scale of anti-mosquito operations according to the level of infestation as well as reports from front-line staff and the public.

     Oviposition traps are set in 44 areas in Hong Kong for monitoring the breeding of Aedes albopictus, which is only one of the mosquito species commonly found in Hong Kong and is active only in the daytime. The index does not capture the activities of Aedes albopictus outside the 44 areas and it also does not measure the prevalence of other kinds of mosquitoes.

     The ovitrap indices for Aedes albopictus in different areas and information on anti-mosquito measures are available on the department website at

Ends/Monday, April 27, 2015
Issued at HKT 19:10