Using confirmed malaria case records from 2021 to 2023, the researchers mapped transmission patterns across Bitung City and identified Lembeh Selatan and Maesa districts as the primary malaria hotspots. The findings matter because they show that malaria control efforts will be far more effective if they focus on high-risk locations instead of applying uniform interventions across all districts.
Why Malaria Remains a Local Health Challenge
Malaria continues to be a public health concern in many parts of Indonesia, particularly in eastern regions where geography and climate support mosquito breeding. Bitung City presents a unique risk profile. It is a coastal and port city located near Mount Dua Sudara and Mount Klabat, with a mix of coastal wetlands, hilly terrain, and densely populated urban zones.
These environmental conditions create favorable habitats for Anopheles mosquitoes, the vectors that transmit malaria. Seasonal rainfall, human mobility related to port activities, and settlement patterns further influence how malaria spreads within the city.
Local health surveillance data had previously shown fluctuating malaria cases in Bitung, but traditional reporting methods made it difficult to see where transmission was actually concentrated. This gap is what the spatial analysis addressed.
How the Study Was Conducted
The research analyzed 379 confirmed malaria cases recorded by the Bitung City Health Office between 2021 and 2023. All cases were included, allowing the researchers to examine the full pattern of malaria transmission over time and space.
Each case was mapped using Geographic Information System (GIS) technology. The spatial data were combined with information on district elevation and population density to calculate the Annual Parasite Incidence (API) for each district. API measures the number of malaria cases per 1,000 people at risk and is commonly used to assess malaria severity.
Rather than relying on complex technical modeling, the analysis focused on clear spatial patterns that could be easily interpreted by public health authorities.
Clear Seasonal and Demographic Patterns
The study found that malaria cases in Bitung City peaked in 2022, with 212 cases, before declining in 2023. Across the three-year period, malaria showed a recurring seasonal pattern, with three main peaks each year:
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March–April
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July–August
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November
These peaks align with periods of increased rainfall and humidity, conditions that support mosquito survival and breeding.
From a demographic perspective, 58 percent of malaria cases occurred among men. The researchers linked this pattern to outdoor and nighttime activities that increase exposure to mosquito bites, a trend that mirrors national malaria statistics in Indonesia.
Lembeh Selatan and Maesa Emerge as Hotspots
Spatial analysis revealed that malaria transmission in Bitung City is highly clustered. Two districts alone accounted for nearly 80 percent of all reported cases.
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Lembeh Selatan District recorded the highest risk, with an API of 15.4 per 1,000 population, placing it firmly in the high-risk category.
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Maesa District showed a moderate API of 3.74 per 1,000, but contributed a large absolute number of cases due to its population size.
In contrast, several districts with high population density reported very few malaria cases. This finding demonstrates that population density alone does not determine malaria risk.
Environment Matters More Than Altitude Alone
The study challenges the assumption that malaria risk is limited to lowland areas. While many cases occurred in districts below 200 meters above sea level, Lembeh Selatan, which includes higher-altitude areas, recorded the most cases overall.
According to the researchers, coastal features such as brackish water pools, mangroves, and swampy areas play a critical role. These environments are ideal breeding grounds for certain Anopheles species, particularly those adapted to coastal ecosystems.
As noted by Dr. Oksfriani Jufri Sumampouw of Sam Ratulangi University, malaria transmission in Bitung is shaped by “location-specific environmental conditions that allow mosquitoes to thrive even outside traditionally defined risk zones.”
Implications for Public Health Policy
The findings have direct implications for malaria control strategies in Bitung City and similar coastal regions. Broad, citywide interventions are unlikely to be efficient. Instead, targeted, hotspot-focused actions are needed.
The study supports:
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Environmental management in coastal and swamp-prone districts
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Strengthened mosquito surveillance in Lembeh Selatan and Maesa
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Community education tailored to high-risk locations
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Routine use of spatial mapping in local health planning
Districts with consistently low malaria incidence can also serve as models of effective prevention, offering lessons for environmental control and health service access.
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