Local Vector Biology

Aedes albopictus

  1. Eggs can withstand drought very well
  2. Breed in small containers such as cans, discarded tyres, tree holes, rock pools and bamboo ends holding small amount of water
  3. Adults rest in shrubby area
  4. Adult has a white stripe on the dorsal surface of thorax and bands on legs.
  5. Although exophilic, adults may also enter into houses
  6. Day biter (Peak : within 2 hours after dawn and before sunset)
  7. Weak flier (about 100m)
  8. Vector of dengue fever

Vector Surveillance

Since 2000, the Food and Environmental Hygiene Department (FEHD) has been using Oviposition Trap (Ovitrap) to detect the presence of adult Aedine mosquitoes. Tools and methodology of dengue vector surveillance is reviewed from time to time and starting from April 2020, a new tool, gravidtrap has been adopted to replace ovitrap for monitoring the dengue vector of Aedine mosquitoes in selected areas. The gravidtrap is a simple device made of a black plastic container of approximately 600ml with a glue board placed inside. It is covered by a black lid with openings and a raised grey cover.

Oviposition Trap (Ovitrap)

To study the distribution of Aedes albopictus, gravidtraps are set in selected areas throughout the territory for monitoring the breeding of these mosquitoes. The percentage of the gravidtraps found positive with breeding of these mosquitoes gives the Gravidtrap Index for Aedes albopictus. The value of Gravidtrap Index for Aedes albopictus indicates the extensiveness of the breeding of the vectors.

At present, there are a total of 64 survey areas selected for the vector surveillance throughout the territory and the following four different indices will be enumerated:

  1. Area Gravidtrap Index for Aedes albopictus (AGI),
  2. Area Density Index for Aedes albopictus (ADI),
  3. Monthly Gravidtrap Index for Aedes albopictus (MGI), and
  4. Monthly Density Index for Aedes albopictus (MDI).

The AGI and ADI indicate the extensiveness of the distribution and density of Aedine mosquitoes respectively in that particular survey area, while the MGI and MDI are enumerated by pooling together all AGIs and ADIs of the same month reflecting the territory-wide situation of Aedes albopictus.

In addition to the areas in the community, surveys of Aedes albopictus are also carried out to cover all major port areas. The following two different groups of indices will be enumerated:

  1. Port / Port Monthly Gravidtrap Index for Aedes albopictus (PGI/PMGI), and
  2. Port / Port Monthly Density Index for Aedes albopictus (PDI/PMDI).

The Port Gravidtrap Index for Aedes albopictus (PGI) indicates the extensiveness of the distribution of Aedine mosquitoes in a particular group of port areas. The Port Monthly Gravidtrap Index for Aedes albopictus (PMGI) is enumerated by pooling together all PGIs of the same month, which reflects the overall degree of occurrence of Aedes albopictus in port areas. Another index, the Port Density Index for Aedes albopictus (PDI) indicates the density of Aedes albopictus in positive traps in a particular group of port areas. The Port Monthly Density Index for Aedes albopictus (PMDI) is enumerated by pooling together all PDIs of the same month, which denotes the overall density of Aedes albopictus in locales detected with Aedine mosquito activities in port areas.

Gravidtrap only detects activities of Aedine mosquitoes in the area where it is set. It cannot be used for detecting activities of other species of mosquitoes (such as Culex and Anopheline mosquitoes). The Gravidtrap Index for Aedes albopictus of an area reflects the extensiveness of the distribution of Aedine mosquitoes and the Density Index for Aedes albopictus of an area reflects the density of Aedes albopictus in the relevant surveillance area during the two weeks of surveillance. Apart from making reference to the relevant Gravidtrap Index and Density Index for Aedes albopictus, parties concerned should take into account other factors (such as the findings and reports on mosquito problem received) in planning and implementing their mosquito prevention and control work.

The period for setting gravidtraps in the survey areas is two weeks. During the survey period, the gravidtraps are collected on a weekly basis. At the end of the first week of surveillance, all the gravidtraps are retrieved and another batch of gravidtraps is set at the same location for surveillance for the second week. The glue boards inside the retrieved gravidtraps are immediately examined for the presence of adult Aedine mosquitoes (“Aedes-positive”) for the purpose of compiling the Gravidtrap Index (First Phase) and Density Index (First Phase). At the end of the second week of surveillance, all the gravidtraps are retrieved and instantly checked for the presence of adult Aedine mosquitoes (“Aedes-positive”) on the glue boards. Data of the two weeks’ surveillance will be combined to obtain the Area Gravidtrap Index (AGI) and Area Density Index (ADI).

FEHD will notify its District Environmental Hygiene Offices and other relevant government departments of the Gravidtrap Indices and Density Indices of various phases once the figures are available, so that they can promptly carry out targeted mosquito prevention and control work. To facilitate public access to the latest survey data, FEHD will announce the phased indices for Aedes albopictus for each of the surveyed areas on the FEHD webpage. Corresponding mosquito prevention and control measures can be taken by the public in a more expeditious manner so as to prevent the spread of dengue fever.

The Gravidtrap Index and Density Index for Aedes albopictus of each surveyed area are released in two phases. Figures released in the first phases are phased indices and the second phase indices represent the AGI and ADI of the surveyed area in that month.

Monthly Ovitrap Index

The Gravidtrap Index for Aedes albopictus is divided into four levels, reflecting the distribution level of the Aedes albopictus. Level 1 (less than 5 per cent) indicates that distribution of Aedes albopictus is not extensive in the area surveyed. Level 2 (5 per cent to less than 20 per cent) indicates that distribution of Aedes albopictus is fairly extensive in the area surveyed. Level 3 (20 per cent to less than 40 per cent) indicates that distribution of Aedes albopictus is extensive in the area surveyed. Level 4 (40 per cent or above) indicates that distribution of Aedes albopictus is very extensive in the area surveyed. Specific preventive and control measures will be initiated accordingly. Management of housing estates, hospitals, schools, construction sites and other venues or properties are also advised to take specific measures to contain mosquito problems in their own properties. The four levels of Gravidtrap Index for Aedes albopictus and actions to be taken by the management are listed in the following table.

Level Gravidtrap Index for Aedes albopictus Actions to be taken
1 G.I. < 5%
(Distribution of Aedes albopictus in the survey area is not extensive)
  • Closely monitor the hygienic condition to prevent breeding of mosquitoes;
  • Conduct weekly inspection to identify breeding / potential breeding places and eliminate such places as far as possible.
  • Public are advised to check and eliminate any possible breeding places within their premises at a frequency not less than once a week (Please go to Advice to the Public for details)
2 5% ≤ G.I. < 20%
(Distribution of Aedes albopictus in the survey area is fairly extensive)
3 20% ≤ G.I. < 40%
(Distribution of Aedes albopictus in the survey area is extensive)
  • To conduct special operations in addition to the regular weekly program to eliminate all breeding / potential breeding places;
  • Private pest control contractor might be employed to control the mosquito problem. Other control measures by using larvicides or adulticides might be feasible.
4 G.I. ≥ 40%
(Distribution of Aedes albopictus in the survey area is very extensive)

The phased Gravidtrap Indices and Density Indices for Aedes albopictus for each surveyed area in September 2021 are provided below:

Hong Kong Island

District

Surveyed area

First Phase Gravidtrap Index First Phase Density Index Area Gravidtrap Index Area Density Index
Central/Western Central and Admiralty 0.0% N/A
Sheung Wan & Sai Ying Pun 11.7% 1.3
Sai Wan 5.6% 1.0
Eastern Chai Wan West 7.0% 1.0 5.3% 1.0
Shau Kei Wan & Sai Wan Ho 3.4% 1.0 2.6% 1.0
North Point 3.6% 1.0 4.5% 1.0
Southern Aberdeen and Ap Lei Chau 14.5% 1.3 11.0% 1.2
Pokfulam 0.0% N/A
Deep Water Bay & Repulse Bay
Wan Chai Tin Hau 5.8% 1.3 8.7% 1.1
Wan Chai North

1.8%

1.0 0.9% 1.0
Happy Valley 3.5% 1.0
Islands
Islands Cheung Chau South
(Formerly: Cheung Chau)
Cheung Chau North
Tung Chung


Kowloon
District Surveyed area First Phase Gravidtrap Index First Phase Density Index Area Gravidtrap Index Area Density Index
Yau Tsim Tsim Sha Tsui 1.6% 1.0
Tsim Sha Tsui East 3.8% 1.0
Mong Kok Mong Kok 12.1% 1.4
Sham Shui Po Cheung Sha Wan
Lai Chi Kok
Sham Shui Po East
Kowloon City Ho Man Tin 7.4% 1.3
Kowloon City North 5.6% 1.0 2.8% 1.0
Hung Hom 19.6% 1.5
Lok Fu West 3.6% 1.0
Kai Tak North 31.7% 1.5
Wong Tai Sin Wong Tai Sin Central 2.0% 1.0
Wong Tai Sin West 3.7% 1.0
Diamond Hill 3.4% 1.0
Ngau Chi Wan 9.3% 1.4
Kwun Tong Kwun Tong Central
Lam Tin
Yau Tong 2.6% 1.0
Kowloon Bay

New Territories
District Surveyed area First Phase Gravidtrap Index First Phase Density Index Area Gravidtrap Index Area Density Index
Sai Kung Tseung Kwan O West
(Formerly: Tseung Kwan O South)
Tseung Kwan O East 5.6% 1.0
Tseung Kwan O North
Sai Kung Town
Ngau Liu & Muk Min Shan
Sha Tin Tai Wai 9.8% 1.0 6.5% 1.0
Sha Tin East 0.0% N/A 4.1% 2.0
Ma On Shan 24.2% 1.9 21.4% 1.5
Sha Tin Town Centre and Fo Tan 11.3% 1.0 9.3% 1.0
Tai Po Tai Po West 5.2% 1.0
Tai Po East 6.1% 1.0 3.1% 1.0
North Fanling 1.8% 1.0
Sheung Shui 13.8% 1.0
Yuen Long Tin Shui Wai 4.9% 1.0
Yuen Kong 0.0% N/A
Yuen Long Town 9.1% 1.0
Ki Lun Shan 0.0% N/A
Sung Shan 4.2% 1.0
Tuen Mun Tuen Mun North 7.7% 1.2
Tuen Mun South 10.9% 2.0
Tuen Mun West 0.0% N/A
So Kwun Wat 10.9% 1.3
Tseun Wan Tsuen Wan Town 5.0% 1.0
Tsuen Wan West 0.0% N/A
Ma Wan 8.0% 1.0
Sheung Kwai Chung
Kwai Tsing Kwai Chung
Lai King
Tsing Yi South
Tsing Yi North

Remarks:
Gravidtrap Index figures in green:                Level I : Gravidtrap Index <5.0% (indicates that the distribution of Aedes albopictus in the survey area is not extensive)
Gravidtrap Index figures in yellow:               Level II : 5.0% ≤ Gravidtrap Index <20.0% (indicates that the distribution of Aedes albopictus in the survey area is fairly extensive)
Gravidtrap Index figures in red:                     Level III : 20.0%≤  Gravidtap Index <40.0% ( indicates that the distribution of Aedes albopictus in the survey area is extensive)
Gravidtrap Index figures in black (bold):    Level IV : Gravidtrap Index ≥40.0% (indicates that the distribution of Aedes albopictus in the survey area is very extensive)

The comparison of Monthly Gravidtrap Index and Monthly Density Index for Aedes albopictus between 2020 and 2021 are shown below.

The comparison of Monthly Gravidtrap Index and Monthly Density Index for Aedes albopictus between 2020 and 2021

The comparison of Monthly Gravidtrap Index and Monthly Density Index for Aedes albopictus between 2020 and 2021

The Monthly Gravidtrap Index for Aedes albopictus for August 2021 is 8.5%.

The Monthly Density Index for Aedes albopictus for August 2021 is 1.2.

Area Gravidtrap Indices and Density Indices for Aedes albopictus for the 64 survey areas in 2021 are provided below:



Hong Kong Island (Map)
District Location Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Central/Western Central and Admiralty AGI 0.0% 0.0% 0.0% 2.0% 5.7% 9.3% 6.7% 7.7%
ADI N/A N/A N/A 1.0 1.5 1.5 1.1 1.3
Sheung Wan & Sai Ying Pun AGI 0.0% 0.0% 0.8% 2.5% 12.5% 11.8% 17.1% 13.4%
ADI N/A N/A 1.0 1.0 1.7 1.6 1.6 1.4
Sai Wan AGI 0.0% 0.0% 1.9% 4.6% 18.2% 25.9% 12.1% 11.5%
ADI N/A N/A 1.0 1.0 1.4 1.6 1.2 1.2
Eastern Chai Wan West AGI 0.0% 0.0% 0.0% 2.6% 9.6% 13.2% 4.4% 4.4% 5.3%
ADI N/A N/A N/A 1.0 1.0 1.0 1.0 1.0 1.0

Shau Kei Wan
Shau Kei Wan & Sai Wan Ho

AGI 0.0% 0.9% 1.7% 4.3% 15.3% 23.1% 17.2% 4.4% 2.6%
ADI N/A 1.0 1.0 1.0 1.2 1.7 1.3 1.0 1.0
North Point AGI 0.0% 0.0% 0.0% 0.9% 8.7% 6.3% 9.1% 5.4% 4.5%

ADI N/A N/A N/A 1.0 1.2 1.0 1.0 1.2 1.0
Southern Aberdeen and Ap Lei Chau AGI 0.0% 0.0% 2.8% 1.8% 13.6% 25.7% 14.7% 9.1% 11.0%
ADI N/A N/A 1.0 1.0 1.7 1.5 1.5 1.3 1.0
Pokfulam AGI 0.0% 0.0% 0.8% 4.3% 15.5% 19.8% 11.7% 21.2%
ADI N/A N/A 1.0 1.0 1.1 1.1 1.1 1.5
Deep Water Bay & Repulse Bay AGI 0.0% 0.0% 0.8% 0.8% 13.9% 17.1% 11.0% 6.9%
ADI N/A N/A 1.0 1.0 1.0 1.0 1.0 1.0
Wanchai Tin Hau AGI 1.0% 1.0% 2.8% 3.8% 16.8% 17.1% 13.7% 6.4% 8.7%
ADI 1.0 1.0 1.0 1.0 1.7 1.0 1.3 1.0 1.0
Wan Chai North AGI 0.0% 0.0% 0.0% 0.0% 5.5% 3.6% 2.7% 0.9% 0.9%
ADI N/A N/A N/A N/A 1.0 1.0 1.0 1.0 1.0
Happy Valley AGI 0.0% 0.0% 0.0% 3.7% 10.9% 12.6% 9.0% 3.7%
ADI N/A N/A N/A 1.0 1.0 1.3 1.0 1.0
Islands (Map)
District Location Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Islands Cheung Chau South
(Formerly: Cheung Chau)
AGI 0.0% 0.0% 2.9% 0.0% 1.4% 7.2% 2.9% 2.9%
ADI N/A N/A 1.0 N/A 1.0 1.0 1.0 1.0
Cheung Chau North AGI 0.0% 0.0% 0.0% 1.5% 7.4% 14.5% 5.8% 11.9%
ADI N/A N/A N/A 1.0 1.0 2.6 1.5 1.0
Tung Chung AGI 1.0% 0.0% 3.1% 6.5% 12.2% 9.0% 3.0% 3.0%
ADI 1.0 N/A 1.3 1.3 1.3 1.2 1.0 1.0
Kowloon (Map)
District Location Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Yau Tsim Tsim Sha Tsui AGI 0.0% 0.0% 4.0% 2.4% 5.5% 4.0% 2.4% 3.2%
ADI N/A N/A 1.0 1.0 1.0 1.0 1.0 1.0
Tsim Sha Tsui East AGI 0.0% 0.0% 2.0% 2.9% 6.7% 8.6% 6.8% 3.8%
ADI N/A N/A 1.0 1.0 1.0 1.2 1.0 1.0
Mong Kok Mong Kok AGI 0.0% 0.0% 0.9% 0.9% 0.9% 3.5% 4.4% 0.0%
ADI N/A N/A 1.0 1.0 1.0 1.0 1.4 N/A
Sham Shui Po Cheung Sha Wan AGI 0.0% 0.0% 0.9% 8.8% 8.0% 13.8% 11.7% 9.6%
ADI N/A N/A 1.0 1.0 1.7 1.2 1.3 1.0
Lai Chi Kok AGI 0.0% 0.0% 2.7% 5.3% 2.7% 5.4% 1.8% 2.7%
ADI N/A N/A 1.7 1.7 1.3 1.0 1.0 1.0
Sham Shui Po East AGI 0.0% 1.0% 0.0% 4.8% 10.7% 19.6% 8.4% 8.4%
ADI N/A 1.0 N/A 1.0 1.0 1.1 1.1 1.0
Kowloon City Ho Man Tin AGI 0.0% 0.0% 2.8% 4.7% 14.3% 15.6% 5.7% 13.0%
ADI N/A N/A 1.0 1.0 1.1 1.3 1.0 1.1
Kowloon City North AGI 0.0% 0.0% 0.0% 2.8% 4.6% 6.4% 0.0% 5.5% 2.8%
ADI N/A N/A N/A 1.0 1.0 1.0 N/A 1.0 1.0
Hung Hom AGI 0.0% 0.0% 1.8% 5.5% 7.1% 17.1% 6.3% 16.7%
ADI N/A N/A 1.0 1.7 1.3 1.2 1.0 1.2
Lok Fu West AGI 0.0% 0.0% 7.8% 16.2% 24.3% 15.3% 8.6% 7.6%
ADI N/A N/A 1.1 1.4 1.6 1.2 1.1 1.2
Kai Tak North AGI 0.0% 0.0% 7.6% 15.9% 13.9% 35.1% 8.6% 35.4%
ADI N/A N/A 1.5 1.4 1.5 1.6 1.3 1.5
Wong Tai Sin Wong Tai Sin Central AGI 0.0% 0.0% 1.9% 6.4% 9.2% 12.6% 7.3% 4.5%
ADI N/A N/A 1.0 1.0 1.4 1.0 1.3 1.2
Wong Tai Sin West AGI 0.0% 0.0% 5.6% 4.7% 10.7% 18.5% 1.9% 6.5%
ADI N/A N/A 1.0 1.0 1.0 1.0 1.0 1.0
Diamond Hill AGI 0.9% 0.0% 0.9% 1.8% 5.2% 6.9% 4.3% 3.4%
ADI 1.0 N/A 1.0 1.0 1.0 1.0 1.0 1.3
Ngau Chi Wan AGI 0.0% 0.0% 6.1% 8.4% 14.2% 13.2% 7.5% 7.5%
ADI N/A N/A 1.0 1.9 1.1 1.1 1.0 1.1
Kwun Tong Kwun Tong Central AGI 0.0% 0.0% 3.1% 8.1% 15.1% 12.9% 14.8% 14.5%
ADI N/A N/A 1.0 1.6 1.4 1.3 1.4 1.1
Lam Tin AGI 0.0% 0.0% 3.4% 7.7% 4.3% 13.0% 5.2% 2.5%
ADI N/A N/A 1.3 1.4 1.6 1.1 1.0 1.3
Yau Tong AGI 0.0% 0.0% 2.7% 1.3% 4.2% 6.6% 4.0% 18.4%
ADI N/A N/A 1.0 1.0 1.0 1.0 1.0 1.1
Kowloon Bay AGI 0.9% 0.8% 0.8% 4.8% 20.5% 15.4% 5.0% 8.5%
ADI 1.0 1.0 1.0 1.0 1.0 1.1 1.0 1.0
New Territories (Map)
District Location Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Sai Kung Tseung Kwan O West
(Formerly: Tseung Kwan O South)
AGI 0.0% 0.0% 5.5% 1.8% 5.6% 5.5% 3.8% 7.3%
ADI N/A N/A 1.0 1.0 1.0 1.0 1.0 1.0
Tseung Kwan O East AGI 0.0% 1.0% 1.0% 3.7% 5.6% 13.2% 5.7% 10.3%
ADI N/A 1.0 1.0 1.0 1.2 1.6 1.7 1.4
Tseung Kwan O North AGI 1.0% 0.0% 11.5% 31.4% 20.2% 14.7% 4.7% 6.7%
ADI 1.0 N/A 1.0 1.6 1.4 1.4 1.0 1.3
Sai Kung Town AGI 0.0% 0.0% 1.9% 10.4% 13.3% 18.9% 9.7% 17.3%
ADI N/A N/A 1.0 1.1 1.1 1.5 1.0 1.3
Ngau Liu & Muk Min Shan AGI 0.0% 0.0% 16.0% 27.1% 24.0% 36.0% 14.0% 12.2%
ADI N/A N/A 1.0 1.2 1.2 1.6 1.4 1.0
Sha Tin Tai Wai AGI 0.0% 0.0% 0.8% 11.3% 9.1% 11.4% 10.7% 3.2% 6.5%
ADI N/A N/A 1.0 1.4 1.3 1.2 1.8 1.3 1.0
Sha Tin East AGI 0.0% 0.0% 0.0% 2.4% 8.0% 8.9% 6.5% 4.0% 4.1%
ADI N/A N/A N/A 1.0 2.6 1.4 1.3 1.0 2.0
Ma On Shan AGI 0.0% 0.8% 0.0% 11.7% 28.1% 43.1% 22.8% 10.3% 21.4%
ADI N/A 1.0 N/A 1.2 1.8 1.8 1.7 1.2 1.5
Sha Tin Town Centre and Fo Tan AGI 0.0% 0.0% 0.0% 0.9% 13.0% 24.3% 11.4% 9.3% 9.3%
ADI N/A N/A N/A 1.0 1.1 1.2 1.0 1.2 1.0
Tai Po Tai Po West AGI 0.0% 0.0% 0.9% 3.5% 8.6% 9.0% 5.2% 11.2%
ADI N/A N/A 1.0 1.0 1.0 1.0 1.0 1.0
Tai Po East AGI 1.0% 0.0% 1.9% 2.0% 8.9% 16.0% 8.7% 16.2% 3.1%
ADI 1.0 N/A 1.0 1.0 1.4 2.1 1.3 1.4 1.0
North Fanling AGI 0.0% 0.0% 4.4% 2.6% 8.6% 19.0% 0.9% 6.4%
ADI N/A N/A 1.0 1.0 1.1 1.5 1.0 1.3
Sheung Shui AGI 0.0% 0.9% 2.7% 7.0% 17.2% 43.5% 7.9% 11.4%
ADI N/A 1.0 1.3 1.1 1.1 1.9 1.2 1.2
Yuen Long Tin Shui Wai AGI 0.0% 0.0% 2.4% 4.8% 10.4% 7.9% 3.2% 6.4%
ADI N/A N/A 1.0 1.0 1.0 1.2 1.0 1.0
Yuen Kong AGI 0.0% 0.0% 2.0% 0.0% 4.1% 6.0% 2.0% 0.0%
ADI N/A N/A 1.0 N/A 1.0 1.0 1.0 N/A
Yuen Long Town AGI 0.0% 0.9% 5.4% 2.7% 11.6% 22.1% 4.5% 7.9%
ADI N/A 1.0 1.0 1.0 1.1 1.4 1.2 1.0
Ki Lun Shan AGI 0.0% 0.0% 6.0% 4.0% 6.1% 8.2% 2.0% 4.3%
ADI N/A N/A 1.0 1.0 1.0 1.5 1.0 1.0
Sung Shan AGI 0.0% 0.0% 6.3% 2.1% 18.4% 29.2% 4.2% 12.5%
ADI N/A N/A 1.0 2.0 1.7 1.8 1.0 1.2
Tuen Mun Tuen Mun North AGI 0.0% 0.0% 10.8% 8.5% 9.3% 5.4% 3.1% 1.5%
ADI N/A N/A 1.4 1.2 1.2 1.0 1.5 1.0
Tuen Mun South AGI 0.0% 0.0% 0.9% 1.8% 10.0% 9.3% 11.1% 8.2%
ADI N/A N/A 1.0 1.0 1.1 1.3 1.2 1.1
Tuen Mun West AGI 0.0% 0.0% 5.2% 3.1% 18.9% 10.4% 7.2% 20.8%
ADI N/A N/A 1.2 1.3 1.2 1.5 1.1 1.2
So Kwun Wat AGI 0.0% 0.0% 3.7% 6.1% 9.6% 25.5% 7.0% 14.0%
ADI N/A N/A 1.3 1.1 1.3 1.4 1.1 1.1
Tsuen Wan Tsuen Wan Town AGI 0.0% 0.0% 3.4% 1.7% 5.1% 6.1% 5.8% 2.5%
ADI N/A N/A 1.0 1.0 1.5 1.7 1.3 1.0
Tseun Wan West AGI 0.0% 0.0% 1.0% 0.9% 7.6% 11.3% 4.8% 2.9%
ADI N/A N/A 1.0 1.0 1.4 1.7 1.0 1.0
Ma Wan AGI 0.0% 4.2% 6.1% 8.0% 14.0% 54.0% 0.0% 20.4%
ADI N/A 1.0 1.0 1.3 1.1 2.1 N/A 1.4
Sheung Kwai Chung AGI 0.0% 0.0% 0.9% 4.6% 4.5% 13.9% 3.7% 7.4%
ADI N/A N/A 1.0 1.0 1.0 1.5 1.3 1.0
Kwai Tsing Sheung Kwai Chung AGI 0.0% 0.0% 0.9% 1.8% 3.5% 7.1% 5.2% 8.0%
ADI N/A N/A 1.0 1.0 1.0 1.0 1.0 1.0
Lai King AGI 0.0% 0.0% 3.8% 3.8% 8.3% 21.0% 14.3% 15.4%
ADI N/A

N/A

1.0 1.0 1.3 1.3 1.2 1.3
Tsing Yi South AGI 0.0% 0.0% 4.3% 6.0% 1.7% 3.4% 3.4% 4.3%
ADI N/A N/A 1.0 1.6 1.0 1.5 1.5 1.0
Tsing Yi North AGI 0.0% 0.9% 3.7% 11.4% 13.8% 16.5% 10.2% 13.8%
ADI N/A 1.0 1.0 1.0 1.1 1.3 1.1 1.1

Remarks:
Gravidtrap Index figures in green:                Level I : Gravidtrap Index <5.0% (indicates that the distribution of Aedes albopictus in the survey area is not extensive)
Gravidtrap Index figures in yellow:               Level II : 5.0% ≤ Gravidtrap Index <20.0% (indicates that the distribution of Aedes albopictus in the survey area is fairly extensive)
Gravidtrap Index figures in red:                     Level III : 20.0%≤  Gravidtap Index <40.0% ( indicates that the distribution of Aedes albopictus in the survey area is extensive)
Gravidtrap Index figures in black (bold):    Level IV : Gravidtrap Index ≥40.0% (indicates that the distribution of Aedes albopictus in the survey area is very extensive)

Number of areas in respective levels of Survey Area Gravidtrap Indices in 2021 are provided below:

Number of survey areas Total number of survey areas Top 5 survey areas at level 3 Top 5 survey areas at level 4
Level 1 Level 2 Level 3 Level 4
0%-<5% 5%-<20% 20%-<40% ≥40%
Jan 64 0 0 0 64 Nil Nil
Feb 64 0 0 0 64 Nil Nil
Mar 51 13 0 0 64 Nil Nil
Apr 43 19 2 0 64
  1. Tseung Kwan O North (31.4%)
  2. Ngau Liu & Muk Min Shan (27.1%)
Nil
May 10 49 5 0 64
  1. Ma On Shan (28.1%)
  2. Lok Fu West (24.3%)
  3. Ngau Liu & Muk Min Shan (24.0%)
  4. Kowloon Bay (20.5%)
  5. Tseung Kwan O North (20.2%)
Nil
Jun 4 47 10 3 64
  1. Ngau Liu & Muk Min Shan (36.0%)
  2. Kai Tak North (35.1%)
  3. Sung Shan (29.2%)
  4. Sai Wan (25.9%)
  5. Aberdeen & Ap Lei Chau (25.7%)
  1. Ma Wan (54.0%)
  2. Sheung Shui (43.5%)
  3. Ma On Shan (43.1%)
Jul 23 40 1 0 64
  1. Ma On Shan (22.8%)
Nil
Aug 21 39 4 0 64
  1. Pokfulam (21.2%)
  2. Kai Tak North (35.4%)
  3. Tuen Mun West (20.8%)
  4. Ma Wan (20.4%)
Nil
Sep
Oct
Nov
Dec

The Port Monthly Gravidtrap Index for Aedes albopictus for August 2021 is 1.3%.

The Port Monthly Density Index for Aedes albopictus for August 2021 is 1.2.

Port Gravidtrap Indices and Port Density Indices for Aedes albopictus in 2021 are provided below:

Port areas (Map)
Port Area Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Hong Kong International Airport PGI 0.0% 0.0% 0.04% 0.5% 0.4% 0.4% 0.2% 0.4%
PDI N/A N/A 1.0 1.1 1.1 1.5 1.0 1.0
Cross Boundary Check Points on Land PGI 0.1% 0.1% 0.6% 2.8% 4.0% 4.4% 2.8% 1.7%
PDI 1.0 1.0 1.0 1.1 1.3 1.4 1.2 1.1
Private Cargo Working Areas PGI 0.0% 0.0% 0.7% 1.7% 4.8% 7.6% 4.8% 4.7%
PDI N/A N/A 1.0 1.0 1.0 1.8 1.3 1.4
Cross Boundary Ferry Piers PGI 0.0% 0.0% 0.0% 0.0% 0.9% 1.0% 1.2% 1.1%
PDI N/A N/A N/A N/A 1.0 2.0 1.0 1.0
Container Terminals PGI 0.0% 0.0% 0.0% 0.1% 0.3% 0.3% 1.1% 0.2%
PDI N/A N/A N/A 1.0 1.0 1.0 1.0 1.0
Public Cargo Working Areas PGI 0.0% 0.0% 0.6% 0.9% 6.0% 4.5% 6.1% 4.8%
PDI N/A N/A 1.0 1.0 1.0 1.1 1.1 1.4

Remarks:
Gravidtrap Index figures in green:                Level I : Gravidtrap Index <5.0% (indicates that the distribution of Aedes albopictus in the survey area is not extensive)
Gravidtrap Index figures in yellow:               Level II : 5.0% ≤ Gravidtrap Index <20.0% (indicates that the distribution of Aedes albopictus in the survey area is fairly extensive)
Gravidtrap Index figures in red:                     Level III : 20.0%≤  Gravidtap Index <40.0% ( indicates that the distribution of Aedes albopictus in the survey area is extensive)
Gravidtrap Index figures in black (bold):    Level IV : Gravidtrap Index ≥40.0% (indicates that the distribution of Aedes albopictus in the survey area is very extensive)

Density Index currently released are only for reference.  The FEHD will collect the data of the density index this year for analysis and will establish a reference level for the corresponding prevention and control measures for the density index after sufficient data has been collected.

For historical information in respect of the previous ovitrap indices, please refer to the followings:

Please click here for the Monthly Ovitrap Index, Gravidtrap Index and Density Index for Aedes albopictus from 2010 to 2020.

Please click here for a graph of the Monthly Ovitrap Index for Aedes albopictus from 2010 to March 2020.

Please click here for the average of the Port Monthly Ovitrap Index for Aedes albopictus from 2010 to March 2020.

Preventive Measures

Advice on mosquito control and prevention

Aedes albopictus (白紋伊蚊) is highly prevalent in Hong Kong. It breeds both in urban and rural areas and their breeding sites can be artificial receptacles like cans, lunch boxes, discarded tyres, clogged surface channels, containers; and naturally occurring tree holes, bamboo stumps and leaf axils.

Killing of mosquito larvae

Prevention is better than cure. As the mosquitoes have to breed in water, it is more effective and efficient to control mosquito at source at its aquatic stage. Pesticide should only be used for killing of mosquito in its breeding place or preventing its breeding if the breeding sources or potential breeding grounds are inaccessible or could not be eliminated for the time being. The followings must be noted for killing mosquito larvae:

  1. Larvicidal oil or larvicide (such as temephos, Bacillus thuringiensis subspecies israelensis etc.) can be applied to stagnant water directly with dosage according to the label instructions.
  2. Higher than required concentration of larvicide or excessive amount of larvicidal oil would not give better result on killing the mosquito larvae.
  3. The pesticides used must have been registered with the Agriculture, Fisheries and Conservation Department.
  4. Depending on the product, larvicide may be applied weekly into the stagnant water until the water has been removed.
  5. Larvicidal oil need not be applied into the stagnant water again if the oil is still present in the water.
  6. Pesticide applicator should put on protective gears including face mask and rubber gloves during pesticide application.

Killing of adult mosquito

Elimination of adult mosquitoes is relatively difficult as compared with that of the larvae. Adult mosquitoes usually disperse from their breeding place and hide in inconspicuous sites. The followings must be noted for killing adult mosquitoes:

Protection against adult mosquitoes

Adult mosquito attacks people for getting blood for laying eggs. The followings have to be noted for getting protection against adult mosquitoes:

  1. Windows and doors could be screened.
  2. Wear long-sleeved clothes and long trousers when going outdoors.
  3. Mosquito bednet could be used when the room is not air-conditioned.
  4. Bodies could be protected from mosquito bite by applying mosquito repellent on the clothes or skin according to label instructions.
  5. Some people may be allergic to insect repellent. Apply small amount of insect repellent to small area of the body to check for any allergic response before using the repellent.

Note: Always read and follow label instructions when using pesticides. Please also refer to the leaflet on Safe Use of Household Pesticides produced by Agriculture, Fisheries and Conservation Department for further information. (Tel. No. 2150 7010, Fax: 2314 2622, e-mail: afcdenq@afcd.gov.hk, Web-site: http://www.afcd.gov.hk). The public can also call the telephone hotline of Food and Environmental Hygiene Department at Tel. No. 2868 0000 for more information on mosquito prevention and control.

Remark on mosquito control

Integrated pest management approach has to be adopted for the prevention and control of mosquito. Elimination of stagnant or/and slow running water is the fundamental and most effective mosquito prevention and control method. Application of chemical including pesticide should be the last resort and temporary measure for killing mosquito larvae. Space spraying against adult mosquitoes by using pesticide should only be carried out when there is an urgent need to reduce the number of adult mosquito such as preventing transmission of mosquito-borne diseases. Ecological impacts have to be taken into consideration for selecting the method(s) for mosquito control.

Advice to Public:

  1. To tidy up their premises and check for any accumulation of water inside their premises;
  2. To remove all unnecessary water collection and eliminate the sources;
  3. To change at least every week the water in flower vases and saucers of potted plants to prevent breeding of mosquitoes. The use of saucers should be avoided whenever possible;
  4. To properly cover all containers that hold water to prevent mosquito from accessing the water;
  5. To properly dispose articles that are able to contain water such as empty lunch boxes, cans and tyres;
  6. To stop storing water along morning walk trails or Government land for irrigation;
  7. To make large holes on tyres used as anti-bumping measure in garage to prevent water trapping or use mark(s) on the parking space to prevent bumping instead.
  8. To contact the district pest control offices or PCAS of FEHD, or pest control companies for assistance in mosquito control or prevention.

Anti-mosquito Measures

Weekly Mosquito Inspection Program

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Weekly Mosquito Inspection Program for Schools pdf txt
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Weekly Mosquito Inspection Program for Domestic Premises (Sinhalese) pdf  
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Weekly Mosquito Inspection Program for Port Facilities pdf txt
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Internet Knowing Aedes albopictus Quiz Game