Statistik Demam Berdarah

01Conceptual Foundation: Why Entomological Indices Matter

Since no curative antiviral therapy exists for dengue, and vaccine deployment remains limited, vector control is the cornerstone of dengue prevention. The entire public health apparatus, from national policy down to individual Puskesmas operations, relies on entomological surveillance data to decide when, where, and how aggressively to intervene. These surveillance data are expressed as standardized indices.

The core principle is straightforward: if you can accurately measure the mosquito population, you can predict the likelihood of dengue transmission in a community before cases occur. The difficulty lies in converting larval counts into reliable predictions of adult mosquito density and, ultimately, disease risk. This gap between what the indices measure (larval infestation) and what actually transmits disease (adult female Aedes aegypti) is a recurring concept tested in public health examinations.

Entomological surveys represent an effective strategy for dengue prevention and control through an understanding of the spatial and temporal distribution of vector populations. In Indonesia, these surveys are conducted using the number of houses and containers as reference units, following WHO guidelines.

02Definitions and Formulas of Key Entomological Indices

2.1 The Stegomyia Indices

The three classical larval indices were originally developed for yellow fever surveillance and later adopted for dengue. They are collectively known as the Stegomyia indices.

Core Index Definition Table

The Breteau Index is generally considered the most informative of the three classical indices because it establishes a relationship between positive containers and the number of premises, providing a combined picture of both the frequency of infestation and the availability of breeding sites. In contrast, the House Index tells you only whether a house is positive or not (binary per-house), and the Container Index tells you the proportion of containers that are positive but disconnects that from the number of houses.

2.2 Indonesia-Specific Index: Angka Bebas Jentik (ABJ) / Free Larva Index (FLI)

Indonesia has added a nationally defined index to the WHO standard set. The Angka Bebas Jentik (ABJ), also called the Free Larva Index (FLI), measures the proportion of houses that are free from larvae:

$$ABJ=\frac{\text{Number of houses free from Aedes larvae}}{\text{Number of houses inspected}}\times 100ABJ\; =\; \backslash frac\{\backslash text\{Number\; of\; houses\; free\; from\; Aedes\; larvae\}\}\{\backslash text\{Number\; of\; houses\; inspected\}\}\; \backslash times\; 100$$

Note that ABJ is the inverse complement of the House Index: $ABJ=100-HIABJ\; =\; 100\; -\; HI$. If the House Index is 30%, then the ABJ is 70%.

The national target for ABJ in Indonesia is 95% or higher (meaning HI should be 5% or lower). Most areas in Indonesia fail to meet this target. For example, a 2024 study in Minahasa Regency found an ABJ of only 71%, and a 2024 evaluation at Puskesmas Meral found an ABJ of 93%, both below the national benchmark.

2.3 Supplementary Indices

Beyond the classical three, several additional indices are used in research and expanded surveillance programs.

Supplementary Indices Table

The Pupae Index was proposed as an improvement over larval indices because pupae are non-feeding, immobile, and therefore less prone to sampling error. In principle, counting pupae provides a more direct estimate of how many adult mosquitoes are about to emerge.

The Ovitrap Index is classified into four levels reflecting the level of Aedes infestation: Level 1 (OI less than 5%, low), Level 2 (OI 5 to 20%, medium), Level 3 (OI 21 to 40%, high), and Level 4 (OI greater than 40%, very high).

03WHO Density Figure (DF) Classification

The WHO Density Figure system provides a composite risk classification by converting raw HI, CI, and BI values into a standardized score on a scale of 1 to 9. Each index is independently mapped to a DF value, and the overall risk is assessed from the combination.

WHO Density Figure Table (Focks 2003, WHO 2003)

Risk Interpretation:

A DF of 1 indicates minimal larval infestation and is the target for effective vector control. In practice, many endemic areas in Indonesia fall in the DF 5 to 8 range, indicating medium to high transmission risk. For example, field surveys in Bengkulu City documented HI values of 44 to 45% (DF 6), CI of 22 to 23% (DF 6), and BI of 96 to 120% (DF 7 to 8).

Critical thresholds historically proposed for dengue prevention are HI of 1% or less, or BI of 5 or less. These thresholds were originally derived from yellow fever transmission models and adopted for dengue due to similarities in vector biology. However, their validity for dengue has been debated. Dengue outbreaks have occurred in Singapore when the national HI was below 1%, while in Fortaleza, Brazil, outbreaks never occurred when HI was below 1%. This discrepancy reflects the imperfect correlation between larval indices and adult mosquito density.

04Limitations of Classical Larval Indices

This is a frequently tested concept. Students must understand that larval indices are imperfect predictors of dengue transmission risk.

A landmark study conducted in Banyumas Regency, Central Java, found that traditionally used larval indices (HI, CI, BI) were inadequate as indicators for dengue virus transmission risk. The study showed that species composition of adult mosquitoes was a better discriminator: competent vector species were dominant in dengue-endemic and sporadic villages, but this difference was not consistently captured by larval indices alone.

Why Larval Indices Fall Short

These limitations are why researchers have proposed pupae indices, ovitrap indices, gravitraps, and adult mosquito surveys as complementary or alternative tools. In Singapore, for example, the house index was abandoned as a primary surveillance metric in favor of gravitrap-based adult surveillance because the consistently low HI (below 1%) rendered it uninformative despite ongoing dengue transmission.

05Indonesian Government Dengue Prevention Strategy

5.1 National Strategic Plan

The Indonesian government has published two national strategic plans for dengue control. The Strategi Nasional Penanggulangan Dengue 2021 to 2025 was launched on July 30, 2021, developed through a collaborative process between the Ministry of Health (Kemenkes), WHO Indonesia, and multiple national stakeholders. This strategy encompassed six strategic pillars:

1. Vector control (mosquito population management)

2. Improved access to treatment and case management

3. Strengthened surveillance and early response

4. Community education and behavioral change

5. Innovation and technology adoption (including Wolbachia and dengue vaccines)

6. Cross-sectoral coordination across levels of government

This strategy is now being updated for the period 2026 to 2030 (Rencana Aksi Nasional Pengendalian Dengue 2026 to 2029), with consultations led by Kemenkes and supported by WHO and Universitas Gadjah Mada from July to September 2025. The updated plan strengthens PSN 3M Plus approaches, promotes technology-based early detection, and expands service coverage to remote areas. The national target is zero dengue deaths by 2030.

5.2 PSN 3M Plus (Pemberantasan Sarang Nyamuk)

PSN 3M Plus is the primary community-based prevention strategy mandated by the Indonesian Ministry of Health. The "3M" refers to three core actions, and "Plus" refers to supplementary measures.

PSN 3M Plus Components

The Ministry of Health has explicitly stated that PSN 3M Plus is more important than fogging (thermal fogging/ultra-low volume insecticide spraying) as a prevention strategy. Fogging kills adult mosquitoes but does not eliminate breeding sites and provides only short-term reduction. Without sustained community action to destroy breeding habitats, the adult mosquito population rebounds within weeks.

5.3 Gerakan 1 Rumah 1 Jumantik (G1R1J)

The Jumantik program (Juru Pemantau Jentik, literally "Larva Monitoring Officer") is a community health volunteer program in which designated individuals conduct routine household larva surveillance. The G1R1J initiative (One House, One Jumantik) aims to assign one person per household to monitor for larvae in and around their home.

Jumantik volunteers inspect water containers, record findings on standardized forms, and report to the Puskesmas. Their data feed into the calculation of ABJ (Angka Bebas Jentik) for each kelurahan (sub-district) and kecamatan (district). A Puskesmas that consistently reports ABJ below the 95% target triggers intensified intervention, including increased larviciding, community mobilization, and potentially fogging.

However, multiple studies have found that the role of Jumantik cadres remains suboptimal. Barriers include lack of training, poor community cooperation, limited budgets for materials, and insufficient supervision. A 2024 evaluation at Puskesmas Meral identified that suboptimal Jumantik cadre performance, inadequate socialization, and limited cross-sector collaboration were the primary obstacles to achieving the national ABJ target.

5.4 Puskesmas-Level Response Protocol

When a dengue case is reported, the Puskesmas follows a structured response protocol.

Puskesmas Dengue Response Steps

The Penyelidikan Epidemiologi is designed to determine whether additional cases exist around the index case and to assess the entomological risk. The standard radius for investigation is 100 meters from the patient's house, reflecting the typical flight range of Aedes aegypti (which rarely exceeds 100 to 200 meters from the breeding site).

5.5 Fogging and Larviciding

Fogging (pengasapan) uses thermal fog generators to disperse insecticide (typically organophosphates or pyrethroids such as malathion or cypermethrin) as a fine aerosol to kill adult mosquitoes on contact. It is used reactively after confirmed cases or outbreaks, not as a routine preventive measure.

Larviciding involves the application of larvicides such as temephos (abate) granules to water containers that cannot be drained or covered. Temephos is applied at a dose of 10 grams per 100 liters of water and can provide protection for up to 3 months. Bacillus thuringiensis israelensis (Bti) is an alternative biological larvicide.

5.6 Wolbachia Program

As covered in the preceding statistics article, the Wolbachia method demonstrated a 77% reduction in dengue incidence and 86% reduction in hospitalization in the Yogyakarta randomized controlled trial (AWED trial). The Indonesian Ministry of Health evaluated the results and approved scale-up. Deployments have expanded beyond Yogyakarta City into Sleman, Bantul, and Denpasar (Bali, starting 2023).

The Wolbachia approach represents a shift from reactive to proactive, self-sustaining vector control. Unlike fogging or larviciding, which require continuous human effort and re-application, Wolbachia-carrying mosquitoes self-propagate in the wild population.

06Practical Application: How to Conduct a Larval Survey

Larval Survey Protocol

The most commonly positive container types in Indonesia are buckets (ember) and bathing tubs (bak mandi). Field studies have consistently shown that these two container types harbor the majority of Aedes larvae.

07Choosing the Right Index

08Traps and High-Yield Pearls

The most common way students answer questions on this topic incorrectly is by assuming that high larval indices always mean high transmission risk, and low indices always mean low risk. This is the central trap. The relationship between larval indices and disease transmission is inconsistent. Outbreaks have occurred in areas with low House Indices (Singapore, HI below 1%), and areas with high indices sometimes do not experience outbreaks because of herd immunity or serotype dynamics.

Another frequent mistake is confusing the direction of ABJ. ABJ is the complement of HI: a high ABJ (95% or above) is the target and indicates that most houses are free from larvae. Students sometimes interpret a "high" ABJ as a bad sign when it is actually the desired outcome.

Students should also understand that the WHO Density Figure table assigns separate DF values for each index independently. A single area can have a different DF for HI, CI, and BI, and the overall risk assessment considers all three together. A discrepancy between indices (for example, low HI but high CI) means that fewer houses are infested, but those that are infested contain a disproportionate number of positive containers. This pattern points to concentrated, high-productivity breeding sites.

Finally, when asked about the "most important" dengue prevention strategy at the community level, the answer in the Indonesian context is PSN 3M Plus, not fogging. The Ministry of Health has explicitly stated that PSN 3M Plus takes priority over fogging. Fogging is reactive and short-lived; PSN 3M Plus is proactive and sustainable. The G1R1J (One House, One Jumantik) program operationalizes this at the household level, and the national ABJ target of 95% or higher is the measurable benchmark for success.