Background On October 23, 2016, 79 dengue fever cases were reported from the Union Council Tarlai to Federal Disease Surveillance and Response Unit Islamabad. A team was established to investigate the suspected dengue outbreak. Objective The aim of this study was to determine the extent of the outbreak and identify the possible risk factors. Methods Active case finding was performed through a house-to-house survey. A case was defined as an acute onset of fever ≥38℃ in a resident of Tarlai from October 2 to November 11, 2016, with a positive dengue virus (nonstructural protein, NS-1) test and any of the two of following signs and symptoms: retroorbital/ocular pain, headache, rash, myalgia, arthralgia, and hemorrhagic manifestations. A structured questionnaire was used to collect data. Age- and sex-matched controls (1:1) were identified from residents in the same area as cases. Blood samples were taken and sent to the National Institute of Health for genotype identification. Results During the active case search, 145 cases of dengue fever were identified by surveying 928 houses from October 23 to November 11, 2016. The attack rate (AR) was 17.0/10,000. The mean age was 34.4 (SD 14.4) years. More than half of the cases were male (80/145, 55.2%). Among all cases, 29% belonged to the 25-34 years age group and the highest AR was found in the 35-44 years age group (35.6/10,000), followed by the 55-64 years age group (35.5/10,000). All five blood samples tested positive for NS-1 (genotype DENV-2). The most frequent presenting signs/symptoms were fever and headache (both 100%). Stagnant water around houses (odds ratio [OR] 4.86, 95% CI 2.94-8.01; P<.001), presence of flower pots in the home (OR 2.73, 95% CI 1.67-4.45; P<.001), and open water containers (OR 2.24, 95% CI 1.36-3.60; P<.001) showed higher odds among cases. Conversely, use of bed nets (OR 0.44, 95% CI 0.25-0.77; P=.003), insecticidal spray (OR 0.33, 95% CI 0.22-0.55; P<.001), door screens (OR 0.27, 95% CI 0.15-0.46; P<.001), mosquito coil/mat (OR 0.26, 95% CI 0.16-0.44; P<.001), and cleanliness of the house (OR 0.12, 95% CI 0.05-0.26; P<.001) showed significant protective effects. Conclusions Stagnant water acting as breeding grounds for vectors was identified as the probable cause of spread of the dengue outbreak. Establishment of surveillance and an early reporting system along with use of protective measures against the vector are strongly recommended.
BACKGROUND On 23rd Oct 2016, 79 dengue fever cases were reported from the Union Council (UC) Tarlai to Federal Disease Surveillance and Response Unit Islamabad. A team was deputed to investigate the suspected dengue outbreak. OBJECTIVE This study was aimed to determine the extent of the outbreak and identify the possible risk factors. METHODS Active case finding was conducted through a house-to-house survey. A case was defined as, acute onset of Fever ≥ 38 ℃ in a resident of Tarlai from Oct 2-Nov 11, 2016, with a positive NS-1 test, and any two of the following signs and symptoms; retro-orbital/ocular pain, headache, rash, myalgia, arthralgia, and hemorrhagic manifestations. A structured questionnaire was used to collect data. Age and sex-matched controls (1:1) were identified from the same area. Blood samples were taken and sent to the National Institute of Health for genotype identification. RESULTS During the active case search, 145 cases of dengue fever were identified by surveying 928 houses from 23rd Oct to 11th Nov 2016. Attack rate (AR) was 17.0/10,000 population. The mean age was 34.4±14.4 years. More than half of the cases were male (n=80, 55.2%). Among all cases, 29% belong to the 25-34 years age group while the highest attack rate was found in 35-44 years (AR 35.6/10,000) followed by 55-64 years (AR 35.5/10,000). All five blood samples tested positive for NS-1 (genotype DENV-2). The most frequent presenting sin/symptom was fever and headache (100%). Stagnant water around houses (OR = 4.86, CI: 2.94 -8.01, P<0.0001), presence of flower pots in-home (OR = 2.73, CI: 1.67-4.45, P<0.0001), and open water container (OR 2.24, CI: 1.36-3.60, P<0.0001) showed higher odds among cases. While. use of bed nets (OR 0.44, CI: 0.25-0.77, P 0.003), insecticidal spray (OR 0.33, CI: 0.22-0.55, P<0.0001), door screening (OR 0.27, CI: 0.15-0.46, P<0.0001), use of mosquito coil/mat (OR 0.26, CI: 0.16-0.44, P<0.0001) and cleanliness in house (OR 0.12, CI: 0.05-0.26, P<0.0001) showed a significant protective effect. CONCLUSIONS Stagnant water acting as breeding grounds for vector was the probable cause of the spread of the outbreak. The establishment of a surveillance and early reporting system and the use of protective measures against the vector is strongly recommended.
Background: In the second week of October 2019, five suspected cases of dengue fever were reported from union council Sohan, Islamabad rural (population 45,747) to the health department, Islamabad Capital Territory (ICT). Outbreak investigation was conducted with the objectives to identify risk factors and to recommend control measures. Methods: Outbreak investigation was conducted from 17 th October to 25 th November 2019. A case was defined as, “fever and two or more of the following signs/symptoms; headache, retro-orbital pain, joint/bone pain, myalgia and petechial rash with NS1 test (Nonstructural Protein 1) positive during 8 th October to 25 th November 2019 among residents of Sohan”. Age and sex-matched controls were recruited from the same neighborhood. All cases were positive for NS1 antigen. Blood samples from five suspected cases were collected and tested for laboratory confirmation. Results: A total of 547 households were surveyed and 85 cases were identified. The mean age was 34.4 years + 16.05 (range 3-71 years). The attack rate was 0.19% whereas the most affected age group was the 45-54 years (AR 0.43%). Males were predominantly affected (n=48 56.5%). Among all cases, 32% (n=27)) had stagnant water inside or around their houses (aOR 2.65, CI 1.20-5.83, P= 0.005), 33% (n=28) were using mosquito repellent (aOR 0.35, CI 0.17-0.70, P <0.001), 31% (n=26) used indoor residual spray insecticide (aOR 0.48, CI 0.24-0.97, P =0.041), and 73% (n=62) used full protective clothing (aOR 0.17, CI 0.05-0.58, P <0.001). All five blood samples were tested positive for NS-1 antigen. Conclusion: The presence of accumulated rainwater in pools and empty receptacles around houses acted as breeding grounds for Aedes aegypti mosquitos and was the most probable cause of this outbreak. Following our recommendations, the health department-initiated mosquito breeding sites control activities through residual insecticide spray and advocacy on the use of protective measures against mosquito bites.
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