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August's monthly ovitrap index for Aedes albopictus edges down further

     The Food and Environmental Hygiene Department (FEHD) announced today (September 25) that the monthly territory-wide ovitrap index for Aedes albopictus, a kind of mosquito which can transmit dengue fever, dropped from 10.4 per cent in July to 6.3 per cent in August, indicating that the infestation of Aedes albopictus in the area surveyed has dropped to a relatively low level.

     An FEHD spokesman said, "The levels of infestation in different areas vary. Among the 44 areas surveyed last month, positive ovitrap indices were recorded in 42 areas, ranging from 1.8 per cent to 16.7 per cent, with the highest in Yuen Chau Kok. As for the port areas, the monthly ovitrap index for Aedes albopictus for August also fell to 1.3 per cent from 2.2 per cent in July.

     "The public should always stay alert to the risk of mosquito-transmitted diseases and step up anti-mosquito measures as the current rainy weather is favourable to breeding of all kinds of mosquito," he stressed.

     The spokesman also advised that the public and estate management bodies should scrub all drains and surface sewers 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. After rainfall, water should be immediately removed from balconies, rooftops and courtyards.

     "People should inspect their homes and surroundings to remove all the 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 added.

     The ovitrap index is divided into four levels, reflecting the infestation level of the Aedes albopictus. Level 1 (< 5 per cent) indicates that infestation of the vector is not extensive in the area surveyed. Level 2 (5 per cent - < 20 per cent) indicates infestation of the mosquito is slightly more extensive in the area surveyed. Level 3 (20 per cent - < 40 per cent) indicates that the 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 Aedes albopictus. The Government will step up the scale of anti-mosquito operations according to the level of infestation.

     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/Thursday, September 25, 2014
Issued at HKT 18:01


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