Spatial Analysis in Detecting Dengue Fever Hotspots in Baguio City

 

Searching Hotspots in a Developing Country

The identification a viral outbreak is one of the most important concerns of every health department. Such as Dengue fever and dengue hemorrhagic fever (DHF) which are acute febrile diseases, found in the tropics like my home country Philippines. Unlike Malaria, dengue is just as prevalent in the urban districts of its range as in rural areas. Each serotype is sufficiently different that there is no cross-protection and epidemics caused by multiple serotypes (hyperendemicity) can occur. Dengue is transmitted to humans by the Aedes aegypti or more rarely the Aedes albopictus mosquito, which feed during the day. And here in the Philippines especially in the Cordillera Administrative Region (CAR) dengue cases usually rises during the rainy season (which starts in June) but according to the Regional Director of the Department of health due to climate change; rains in the Cordillera are now whole year round. And because of these alarming increase of  61% nationwide and 100% increase in CAR in 2010, the Philippine Health Department  started a anti dengue campaign know as the Five S . The “Five S Program” stands for 1.) Seek and destroy breading grounds, 2.)Self-protection,  3.) Seek early treatment, 4.) Say no to discriminate fogging 5.) Surveillance and monitoring. From the fifth S which is surveillance and monitoring comes one special statistical tool used known as the spacial distribution in determining the hotspots. Hotspots policing is an effective viral outbreak strategy and it has become a health strategy for reducing viral outbreak in the United States. The hotspots perspective suggests that the health workers can reduce a disease by focusing their limited resources on the small number of places that generate a majority of health problems. Spatial distribution on the other hand is the location of measurements observed in geographical space. The technique for analysing geographically-reference data sets to extract or generate new geographical information or entities together with their spatial dimensions, known as spatial analysis.

Spatial distribution helps to reveal a phenomena such as the cholera outbreak in London, by which has been identified by John Snow (1854), that the outbreak was centered    at a specific location, the water pump. Interviews confirmed that the most number of cases were from people who would regularly walk and pass by the pump and take a drink. Upon knowing the cause of cholera outbreak, preventive measures were made, such as the removal of the handle of the water pump, which resulted to complete eradication of cholera outbreak overnight

From the study of one of my schoolmate which is the use of nearest neighbor hierarchical cluster analysis to detect crime hotspots in the city of Baguio (City located in CAR) I got the interest to have a similar study which is the Detection of Dengue Fever Incidence in the city of Baguio using Spacial Analysis. And I found it timely  because by providing information that could guide the leadership of Baguio City heath department, particularly the health workers focusing in surveillance and monitoring, on how to maximize the use of their limited resources in addressing reportable   diseases. It is expected that by focusing manpower and resources on areas identified as hotspots during peak hours could reduced the incident substantially. Also, the need of surveillance and monitoring of the spread of the disease is a great need in acquiring valuable information. And the hotspots   being obtained could be used in preventing, planning and awareness on the spread of the virus.

The study I conducted was carried out in the 128 barangays/towns of the City of Baguio. Focusing on the patient whose had been diagnosed with dengue fever, in which their coordinates of their addresses and the month of their admission to the hospital are being monitored as the pertinent data of the study.

          The statistical tool used in the study is the Spatial Analysis, and Hierarchical Cluster Analysis to determine the spatial maps and hotspots of the patient each year from 2008, 2009 and 2010.The spatial maps include are Natural Neighbor Map, and Geary’s map in enable to use the   List Index of Spatial Association and in determining the specific hotspots.  Hierarchical Cluster Analysis Dendogram to utilize the clustered month in which dengue fever is more prevalent.

From the compute NNI which are lower than 1 and supported by Z score test signified that there are clustered groups being found in the year 2008, 2009 and 2010.

Ten clustered groups are considered dengue hotspots in the year 2008. While in 2009   there were also ten identified dengue hotspots however the total area of contamination is slightly greater which signifies that there were more towns affected by dengue virus in 2009 than 2008.   Year 2010 the most dispersed among the three  detected 16 dengue hotspots   in which covers almost he whole City except the eastern part of Baguio. From which dengue fever can be considered to be epidemic because of the tremendous increase and area of contamination of patients having dengue fever.

Location of identified 2008 dengue hotspots

 

Location of identified 2009 dengue hotspots

Location of identified 20010 dengue hotspots

The Hierarchical Cluster Analysis Dendogram reveals that the peak season for dengue cases is on the month of July and August. However there were significant numbers of dengue cases in the month of June, January, September and October   in which dengue still prevalent in the City. The months of February, March, April, May, November and December have the least number of incidences. 

HierarchicalCluster Analysis Dendogram

Upon survey from some of the dengue prone barangays it is noteworthy that the garbage; unattended water containers, canals, roof gutters , flowers pots   and stagnant water from water banks are some cause of mosquitoes to breed freely especially on the barangays which are dengue hotspots for two to three consecutive years.

Thus enable to minimize and to stop the life cycle of this dengue carrying mosquitoes it is highly recommended that efforts from the city officials should be focused on the barangays that are considered as dengue hotspots for two to three consecutive years, especially in the month of January, June, July, August, September and October. And every resident should check and clean their surrounding from time to time to avoid the spread of the dreaded disease.

 From the study I found out how valuable statistics in our daily life, there are lots of formulas, theory and unending interpretations and most of them are estimates, from which other individuals may not want to have it as a vocation. But as for me I found it so fascinating, like proving not all things you see are for real this may not be significant enough to depend on.  And who knows statistics can be an effective medicine in our ailing soul and heart.