November's monthly ovitrap index for Aedes albopictus drops to low level

     The Food and Environmental Hygiene Department (FEHD) announced today (December 18) that the monthly territory-wide ovitrap index for Aedes albopictus, a kind of mosquito which can transmit dengue fever (DF), dropped from 2.2 per cent in October to 0.4 per cent in November, indicating that the infestation of Aedes albopictus in the areas surveyed stayed at a relatively low level and the infestation of the vector is not extensive.

    An FEHD spokesman said, "Among the 44 areas surveyed last month, positive ovitrap indices were recorded in seven areas, ranging from 1.7 per cent to 3.8 per cent, with the highest level being in Ho Man Tin. As for the port areas, the monthly ovitrap index for Aedes albopictus for November stayed at 0.1 per cent as in October.

    "Despite the recent cooler weather, and the relatively lower index levels for Aedes albopictus recorded in November, in view of the confirmation of three DF local cases earlier and the fact that the number of DF cases in neighbouring areas continues to stay at a high level, the community must remain vigilant. The Government and the community 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 FEHD's city-wide thematic mosquito prevention and control special operation which commenced on October 20 will be extended throughout the winter season and last till January 23, 2015. Mosquito control work will also be enhanced during the year-end clean-up operation, which is due to commence on January 26, 2015. The district offices of the FEHD will target areas which have drawn particular concern, such as single-block buildings, village houses, large residential estates, construction sites and cargo/container terminals and handling areas at port areas, and intensify mosquito prevention and control work at those places," he said.

    The best way to prevent DF is to prevent mosquito breeding. The spokesman advised the public to inspect their homes and surroundings to remove all 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. 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.

    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.

     Moreover, travellers are advised to take the following precautionary measures when visiting areas where mosquito-borne diseases are prevalent during the Christmas and New Year holidays:

* Wear light-coloured, long-sleeved clothes and trousers;
* Use insect repellent over exposed parts of the body when outdoors; and
* Use mosquito screens or nets when a room is not air-conditioned.

     Travellers returning from these places should seek medical advice if they have symptoms such as fever, severe headache or muscle and joint pain. They should also inform their doctor of their travel history.

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

Ends/Thursday, December 18, 2014
Issued at HKT 16:00