The changing epidemiological pattern of Dengue in Swat, Khyber Pakhtunkhwa.

Background: Pakistan is suffering from dengue fever since 1994. In the country, major dengue outbreaks have been documented in 2010, 2011 and 2013 in Punjab (Lahore) and Sindh (Karachi) Provinces. District Swat was hit for the first time by dengue virus in 2013, claiming 57 deaths and 8000 morbidities. The molecular and entomological aspects along with the ecological and social context of the dengue outbreaks were investigated in this study.

Method: In addition to entomological survey, the data collected from patients' files (Saidu Sharif Teaching Hospital, Swat) and by directly questioning the patients (field data) was analyzed for epidemiological trends, molecular identification (RT-PCR based serotyping of DENV), clinical profile, socioeconomic status (SES) and demographic features.

Results: The peak prevalence of dengue was documented in September (56% in 2013, 38% in 2014) and October (33% in 2013, 24% in 2014), whereas in 2015, in October (54.5%) and November (30.5%). The serotype 3 (≤60%) and serotype 2 (≤40%) were found dominant in the area. Among the reported patients (5513), 69% were males and 31% females. Majority of them were found in the age of 14-30 years (52.5%) as compared to 31-60 years (34.5%) (Chi-square: 3219.463, p-value: 0.00). About 63% cases reported in low SES. Among the different categories of government employees affected with dengue, majority (4%) were belonging to health department (Chi-square: 4541.011, p-value: 0.00). Similarly, dengue targeted the dwellers living in multiple-storey houses (65%) as compared to those in the single-storeyed houses (35%) (Chi-square: 495.630, p-value: 0.00). The overall death toll observed was of 57 persons. Dengue prevailed more (38.4%) among low qualified individuals as compared to high qualified (11.5%) (Chi-square: 884.315, p-value: 0.00).

Conclusion: Our analysis indicated a decrease in the epidemiological trend of dengue (now) in the area, though initially it was observed affecting all types of communities on a larger scale. However, the DENV-2 and DENV-3 were dominantly circulating in the area and the prevalence (with usual peaks in post-monsoon) found high in males, illiterate (less educated) individuals and in those with low SES. Urbanization, infected human travelling, climate change, socioeconomic, sociodemographic as well as the wide range adaptation of vector mosquitoes, altogether, are the important factors playing role in the expansion of dengue. Further studies are needed to determine the association of these variables with the dengue spread in the area.