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).

Please click here for details of Gravidtrap survey methodology

Brief of Gravidtrap Indices and Density Indices in March 2024

The Monthly Gravidtrap Index for Aedes albopictus mosquitoes in March 2024 was 0.3 per cent. The index in March remained at the lowest Level 1, indicating that the distribution of Aedes albopictus mosquitoes in the areas surveyed was not extensive. All the 64 survey areas were recorded with a Gravidtrap Index lower than the alert level of 20 per cent. Moreover, the Monthly Density Index for Aedes albopictus in March was 1, which represented that an average of one Aedes albopictus adult was found in the Aedes-positive Gravidtraps, indicating that the number of adult Aedes albopictus was not abundant in the survey areas.

The phased Gravidtrap Indices and Density Indices for Aedes albopictus for each surveyed area in April 2024 are provided below:

Hong Kong Island

District

Survey area

First Phase Gravidtrap Index First Phase Density Index Area Gravidtrap Index Area Density Index
Central/ Western Central and Admiralty 5.7% 1.7
Sheung Wan and Sai Ying Pun
Sai Wan
Eastern Chai Wan West
Shau Kei Wan and Sai Wan Ho
North Point
Southern Aberdeen and Ap Lei Chau 1.9% 1.0
Pokfulam
Deep Water Bay and Repulse Bay
Wan Chai Tin Hau 3.6% 2.0
Wan Chai North
Happy Valley
Islands
Islands Cheung Chau South
(Formerly: Cheung Chau)
Cheung Chau North
Tung Chung
Kowloon
District Survey area First Phase Gravidtrap Index First Phase Density Index Area Gravidtrap Index Area Density Index
Yau Tsim Tsim Sha Tsui
Tsim Sha Tsui East 0.0% N/A
Mong Kok Mong Kok
Sham Shui Po Cheung Sha Wan
Lai Chi Kok
Sham Shui Po East
Kowloon City Ho Man Tin 3.8% 1.0
Kowloon City North
Hung Hom
Lok Fu West
Kai Tak North
Wong Tai Sin Wong Tai Sin Central 2.0% 1.0
Wong Tai Sin West
Diamond Hill 0.0% N/A
Ngau Chi Wan
Kwun Tong Kwun Tong Central
Lam Tin
Yau Tong
Kowloon Bay
New Territories
District Survey 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
Tseung Kwan O North
Sai Kung Town
Ngau Liu and Muk Min Shan
Sha Tin Tai Wai 1.6% 1.0
Sha Tin East 4.9% 1.0
Ma On Shan
Sha Tin Town Centre and Fo Tan 0.0% N/A
Tai Po Tai Po West 3.5% 1.0
Tai Po East
North Fanling
Sheung Shui 9.7% 1.2
Yuen Long Tin Shui Wai 1.6% 1.0
Yuen Kong
Yuen Long Town 0.0% N/A
Ki Lun Shan
Sung Shan
Tuen Mun Tuen Mun North
Tuen Mun South
Tuen Mun West 0.0% N/A
So Kwun Wat 11.8% 1.0
Tseun Wan Tsuen Wan Town
Tsuen Wan West
Ma Wan
Sheung Kwai Chung 3.7% 1.0
Kwai Tsing Kwai Chung
Lai King
Tsing Yi South
Tsing Yi North

Index value remarks:

Colour Gravidtrap Index Density Index
Green:Level I Gravidtrap Index < 5.0% [indicates that the distribution of Aedes albopictus is not extensive] 1.0 ≤ Density Index ≤ 1.5 [Aedes albopictus is not abundant in the locations with positive Gravidtraps]
Yellow:Level II 5.0% ≤ Gravidtrap Index < 20.0% [indicates that the distribution of Aedes albopictus is fairly extensive] 1.6 ≤ Density Index ≤ 2.4 [Aedes albopictus is slightly abundant in the locations with positive Gravidtraps]
Red:Level III 20.0% ≤ Gravidtrap Index < 40.0% [indicates that the distribution of Aedes albopictus is extensive]

Density Index ≥ 2.5 [Aedes albopictus is abundant in the locations with positive Gravidtraps]

Purple:Level IV Gravidtrap Index ≥ 40.0% [indicates that the distribution of Aedes albopictus is very extensive]

Number of areas in respective levels of Survey Area Gravidtrap Indices in 2024 are provided below:

Number of survey areas recorded with respective Index Level 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 63 1 0 0 64 Nil Nil
Mar 64 0 0 0 64 Nil Nil

Number of survey areas recorded with Area Gravidtrap Index reaching level III and Level IV in 2024 is provided below:


Image of Number of survey areas recorded with Area Gravidtrap Index reaching level III & level IV 2024

Please click here for annual hotspot map on survey locations with Area Gravidtrap Index (AGI) reaching Level III and Level IV.

Comparison of Monthly Gravidtrap Index and Monthly Density Index for Aedes albopictus (2021 to 2023 and 2024) are provided below:

Please click here for Record of Indices in 2024.

Information of Major Port Areas

The Port Monthly Gravidtrap Index and the Port Monthly Density Index for Aedes albopictus for March 2024 are 0.2% and 1.0 respectively.

Port Gravidtrap Indices and Port Density Indices for Aedes albopictus in 2024 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% 0.0%
PDI N/A N/A N/A
Cross Boundary Check Points on Land PGI 0.4% 0.0% 0.3%
PDI 1.0 N/A 1.0
Private Cargo Working Areas PGI 0.3% 0.0% 0.6%
PDI 1.0 N/A 1.0
Cross Boundary Ferry Terminals PGI 0.0% 0.0% 0.5%
PDI N/A N/A 1.0
Container Terminals PGI 0.0% 0.0% 0.1%
PDI N/A N/A 1.0
Public Cargo Working Areas PGI 0.2% 0.0% 0.4%
PDI 1.0 N/A 1.0

Index value remarks:

Colour Gravidtrap Index Density Index
Green:Level I Gravidtrap Index < 5.0% [indicates that the distribution of Aedes albopictus is not extensive] 1.0 ≤ Density Index ≤ 1.5 [Aedes albopictus is not abundant in the locations with positive Gravidtraps]
Yellow:Level II 5.0% ≤ Gravidtrap Index < 20.0% [indicates that the distribution of Aedes albopictus is fairly extensive] 1.6 ≤ Density Index ≤ 2.4 [Aedes albopictus is slightly abundant in the locations with positive Gravidtraps]
Red:Level III 20.0% ≤ Gravidtrap Index < 40.0% [indicates that the distribution of Aedes albopictus is extensive]

Density Index ≥ 2.5 [Aedes albopictus is abundant in the locations with positive Gravidtraps]

Purple:Level IV Gravidtrap Index ≥ 40.0% [indicates that the distribution of Aedes albopictus is very extensive]

Historical information in respect of  Ovitrap indices, Gravidtrap Indices and Density Indices 

Please click here for the Monthly Ovitrap Index, Gravidtrap Index and Density Index for Aedes albopictus from 2013 to 2023.

Please click here for a graph of comparison of Monthly Ovitrap Index for Aedes albopictus: 2010 to 2019 and 2020.

Please click here for a graph of comparison of Monthly Gravidtrap Index for Aedes albopictus: 2020 to 2022 and 2023.

Please click here for a graph of comparison of Monthly Density Index for Aedes albopictus: 2020 to 2022 and 2023.

Please click here for the Port Monthly Ovitrap Index, Gravidtrap Index and Density Index for Aedes albopictus from 2013 to 2023.