At present, there are a total of 62 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 / Monthly Port Gravidtrap Index for Aedes albopictus (PGI/MPGI), and
  2. Port / Monthly Port Density Index for Aedes albopictus (PDI/MPDI).

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 Monthly Port Gravidtrap Index for Aedes albopictus (MPGI) 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 Monthly Port Density Index for Aedes albopictus (MPDI) 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.

The Gravidtrap Index for Aedes albopictus is divided into four levels, reflecting the infestation level of the Aedes albopictus. Level 1 (less than 5 per cent) indicates that infestation of the mosquito is not extensive in the area surveyed. Level 2 (5 per cent to less than 20 per cent) indicates that infestation of the mosquito is slightly more extensive in the area surveyed. Level 3 (20 per cent to less than 40 per cent) indicates that infestation of the mosquito exceeds one-fifth of the area surveyed. Level 4 (40 per cent or above) indicates that almost half of the surveyed area is infested with the mosquito. 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%
  • 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%
3 20% ≤ G.I. < 40%
  • 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%

Area Gravidtrap Indices and Density Indices for Aedes albopictus for the 62 survey areas in 2020 are provided below:

Hong Kong Island (Map)
District Location   Apr May Jun Jul Aug Sep Oct Nov Dec
Central/Western Central and Admiralty AGI 1.0% 2.0% 9.5% 4.1%
ADI 1.0  1.0  1.3  1.3          
Sheung Wan & Sai Ying Pun AGI 3.4%  12.5%  15.0%  5.0%          
ADI 1.0 1.3 1.4 1.0
Sai Wan AGI 3.7%  4.7%  22.4%  7.5%          
ADI 1.3 1.4 1.8 1.1
Eastern Chai Wan West AGI 0.0% 2.7% 16.1% 3.5%
ADI N/A  1.0  1.1 1.0           

Shau Kei Wan
& Sai Wan Ho

AGI 1.8%  17.1%  26.8%  19.4%          
ADI 1.5 1.3 1.4 1.9
North Point AGI 0.0% 12.0%  30.4%  13.4%          
ADI N/A 1.3 1.5 1.3
Southern Aberdeen and Ap Lei Chau AGI 2.8% 18.3% 17.3% 12.7%
ADI 1.0  1.4  1.1 1.5          
Pokfulam AGI 3.5%  5.3%  26.4%  10.6%          
ADI 1.0 1.0 1.6 1.3
Deep Water Bay & Repulse Bay AGI 3.4%  11.5%  20.7% 9.4%          
ADI 1.0 1.0 1.0 1.0
Wanchai Tin Hau AGI 7.0% 11.3% 12.6% 12.0%
ADI 1.4  2.4  2.0 1.3          
Wan Chai North AGI 0.0%  2.7%  0.9%  0.0%          
ADI N/A 1.0 2.0 N/A
Happy Valley AGI 3.6%  1.9%  20.2%  5.6%          
ADI 1.0 1.0 1.2 1.2
Islands (Map)
District Location Apr May Jun Jul Aug Sep Oct Nov Dec
Islands

Cheung Chau South
(Formerly: Cheung Chau)

AGI 25.6% 15.8% 15.7%
ADI 1.4  1.7  1.5            
Cheung Chau North AGI N/A N/A 20.9%
ADI N/A N/A 2.4
Tung Chung AGI 8.1%  10.0%  11.0%            
ADI 1.5 1.3 1.5
Kowloon (Map)
District Location Apr May Jun Jul Aug Sep Oct Nov Dec
Yau Tsim Tsim Sha Tsui AGI 4.9% 12.8% 9.4% 3.2%
ADI 1.0  1.8 1.0  1.0          
Tsim Sha Tsui East AGI 0.0%   3.9%  24.5%  4.8%          
ADI N/A 1.3 1.5 1.0
Mong Kok Mong Kok AGI 1.7% 5.0% 6.7% 4.2%
ADI 1.0  1.0  1.1  1.6          
Sham Shui Po Cheung Sha Wan AGI 2.9% 9.5% 10.4%
ADI 1.0  1.0  1.4            
Lai Chi Kok AGI 7.1%  8.9%  11.6%            
ADI 2.5 2.1 2.0
Sham Shui Po East AGI 0.9%  10.2%  18.3%            
ADI 1.0 1.3 1.2
Kowloon City Ho Man Tin AGI 1.9% 8.5% 19.4% 6.5%
ADI 1.0  1.2  1.3  1.7          
Kowloon City North AGI 3.6%  5.5%  7.4%            
ADI 1.0 1.0 1.0
Hung Hom AGI 1.8% 7.9% 18.8% 10.9%
ADI 1.0  1.1  1.2  1.1          
Lok Fu West AGI 5.2% 5.8% 26.3% 7.6%
ADI 1.3  1.1  1.4  1.1          
Kai Tak North AGI 8.6%  11.1%  26.6%  10.3%          
ADI 1.1 1.7 1.7 1.3
Wong Tai Sin Wong Tai Sin Central AGI 6.7% 10.5% 19.4% 13.6%
ADI 1.0  1.3  1.7  1.6          
Wong Tai Sin West AGI N/A N/A 25.0% 7.5%
ADI N/A N/A 1.0 1.1
Diamond Hill AGI 0.0%  0.9%  15.5%  9.6%          
ADI N/A 2.0 1.0 1.2
Ngau Chi Wan AGI 1.0%  5.7%  23.6%  11.7%          
ADI 1.0 1.0 1.6 1.2
Kwun Tong Kwun Tong Central AGI 10.2% 18.8% 17.1%
ADI 1.4  1.2  1.4            
Lam Tin AGI 8.4%  10.9%  21.8%            
ADI 1.1 1.1 1.6
Yau Tong AGI 1.4% 12.2% 7.1% 9.5%
ADI 1.0  1.1  1.0  1.0          
Kowloon Bay AGI 4.2%  9.8%  17.5%            
ADI 1.0 1.3 1.1
New Territories (Map)
District Location Apr May Jun Jul Aug Sep Oct Nov Dec
Sai Kung Tseung Kwan O West
(Formerly: Tseung Kwan O South)
AGI 6.3% 5.6% 10.4%
ADI 1.1  1.0  1.2            
Tseung Kwan O East AGI N/A N/A 23.5% 8.7%
ADI N/A N/A 2.0 1.1
Tseung Kwan O North AGI 7.7% 15.2%   32.0%            
ADI 1.3 1.2 1.6
Sai Kung Town AGI 13.9% 21.3% 19.4%
ADI 1.1 1.2 1.3
Ngau Liu & Muk Min Shan AGI N/A N/A   32.7% 16.3%           
ADI N/A N/A 1.9 1.8
Sha Tin Tai Wai AGI 10.5% 10.4% 18.5% 10.7%
ADI 1.2  1.2  1.1

1.2

         
Sha Tin East AGI 1.6%  20.2%  14.5%  6.6%          
ADI 1.0 2.0 2.2 1.3
Ma On Shan AGI 8.1% 12.1% 28.1% 8.6%
ADI 1.2  1.9  2.0  1.2          
Sha Tin Town Centre and Fo Tan AGI 6.0%  6.5%  21.0%  17.0%          
ADI 1.3 1.1 1.8 1.8
Tai Po Tai Po North AGI 1.7% 5.0% 19.2% 1.7%
ADI 1.0  1.0 1.0  4.5          
North Fanling AGI 5.2% 4.3% 17.4% 5.4%
ADI 1.5  1.0  1.6  1.3          
Sheung Shui AGI 3.5%  10.5%  34.2%  13.8%          
ADI 1.0 1.1 1.8

1.4

Yuen Long Tin Shui Wai AGI 8.0% 6.4% 5.6% 2.4%
ADI 1.0  1.0  1.1  1.0          
Yuen Kong AGI 2.0%  2.0%  8.0%  0.0%          
ADI 1.0 1.0 1.0 N/A
Yuen Long Town AGI 3.6%  6.5% 15.2% 10.5%
ADI 1.0 1.1 1.1 1.5
Ki Lun Shan AGI N/A N/A  29.2%  6.4%          
ADI N/A N/A 2.6 1.0
Tuen Mun Tuen Mun North AGI 2.3% 18.5% 11.5% 5.4%
ADI 1.0  1.9  1.3  1.1          
Tuen Mun South AGI 0.9%  18.2%  14.7%  9.1%          
ADI 1.0 1.3 1.3 1.0
Tuen Mun West AGI 3.1%  15.6% 21.9% 6.1%
ADI 1.0  2.1  1.9 1.0          
So Kwun Wat AGI 2.6%  12.1%  21.6%  7.8%          
ADI 1.3 1.1 1.4 1.1
Tsuen Wan Tsuen Wan Town AGI 0.8% 4.2% 17.6% 5.0%
ADI 1.0  1.4  1.7  1.0          
Tsuen Wan West AGI 9.0% 12.0%  23.8%  2.9%          
ADI 1.3 1.1 1.7 1.0
Ma Wan AGI 6.1% 27.1% 32.0% 12.2%
ADI 1.0  1.2  1.6  1.2          
Sheung Kwai Chung AGI 3.7%  5.6%  5.7%            
ADI 1.0 1.2 1.3
Kwai Tsing Kwai Chung AGI 5.4% 9.6% 5.4%
ADI 1.0  1.0  1.0            
Lai King AGI 17.1%  21.0%  25.0%            
ADI 1.3 1.2 2.0
Tsing Yi South AGI 5.2% 12.1% 23.5%
ADI 1.3  1.4  1.6            
Tsing Yi North AGI 1.8%  5.6%  18.4%            
ADI 1.0 1.2 2.0
Port areas (Map)
Port Area Apr May Jun Jul Aug Sep Oct Nov Dec
Hong Kong International Airport PGI 0.2% 0.8% 1.4%
PDI  1.2  1.2  1.1            
Cross Boundary Check Points on Land PGI  0.9%  4.7%  7.2%            
PDI 1.0 1.5 1.5
Private Cargo Working Areas PGI 1.3% 7.3% 11.3%
PDI  1.0  1.1  1.3            
Cross Boundary Ferry Piers PGI  0.5%  3.6%  2.5%            
PDI 1.0 1.2 1.0
Container Terminals PGI

0.1%

0.9% 0.8%
PDI  1.0  1.1  1.0            
Public Cargo Working Areas PGI  0.3%  4.9%  10.2%            
PDI 1.0 1.1 1.1

The Monthly Gravidtrap Index for Aedes albopictus for June 2020 is 18.1%.

The Monthly Density Index for Aedes albopictus for June 2020 is 1.5.

The Port Monthly Gravidtrap Index for Aedes albopictus for June 2020 is 3.5%.

The Port Monthly Density Index for Aedes albopictus for June 2020 is 1.3.

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

The comparison of Monthly Ovitrap Index for Aedes albopictus between 2020 and average of 2010 to 2019 are shown below.

Monthly Gravitrap Index

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

Please click here for the average 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.

Area Ovitrap Index for Aedes albopictus for the 57 locations are shown in the following maps :

Port Ovitrap Index for the six groups of port areas are shown in the following map :