Seroepidemiology of dengue fever in Khyber Pakhtunkhawa, Pakistan.
Dengue is the most important vector-borne disease in many different parts of the world and is expanding into other areas of the globe without hindrance. The morbidity and mortality due to dengue complications are increasing globally at an alarming rate. Although transmission of the dengue virus has been documented in well-characterized areas of Pakistan, its incidence in Khyber Pakhtunkhawa has not been characterized. To address this issue we aimed to determine the seroprevalence of dengue (IgM and IgG) antibodies and the disease symptoms in the population of Khyber Pakhtunkhawa, and to investigate the incidence of dengue fever in different seasons and in urban as well as in rural areas. From August to October 2011, data of suspected dengue patients were collected from different primary, secondary, and tertiary collection centers situated in Khyber Pakhtunkhawa in order to determine the actual seroprevalence of dengue antibodies (IgM and IgG) in Khyber Pakhtunkhawa. A total 612 subjects with a suspected infection were enrolled in our study. Of the 612 suspected cases, 319 were found positive for dengue IgG, IgM, or both IgG and IgM. The overall weighted prevalence of dengue-specific antibodies (IgM and/or IgG) was 52.12%. Overall, of the 52.12%, 31.86% (95% confidence interval (CI) 28.17-35.55) were positive for dengue IgM and 20.26% (95% CI 17.03-23.39) were positive for dengue IgG. Only 23 (3.75%) samples showed both IgG and IgM antibodies. A higher prevalence of IgM (39.35%, 95% CI 32.84-45.86) and IgG (22.42%, 95% CI 16.86-27.98) antibodies was found in the age group 21-30 years as compared to the children age group (≤10 years) and the oldest age group (≥51 years). The mean age of the febrile cohort was 53.16 ± 44.22 years, ranging from 4 to 85 years. Age group was not statistically associated with IgM (p=0.64) or IgG (p=0.49) positivity. A higher seroprevalence of IgM (37.24%, 95%CI 32.84-45.86) was observed in males as compared to females (IgM 17.88%, 95% CI 11.11-24.65) while higher seroprevalnce of IgG (22.76%, 95% CI 15.35-30.17) was seen in females as compared to males (IgG 17.58%, 95% CI 14.21-20.95). Gender was not significantly associated with IgM (p=0.06) or IgG (p=0.53) positivity. Dengue IgM (35.38%, 95% CI 38.61-62.91) and IgG (50.76%, 95% CI 38.61-62.91) were higher in patients who had a history of travel to a dengue endemic area as compared to those who did not (IgM 33%, 95% CI 29.06-36.94, and IgG 15%, 95% CI 12.01-17.99). History of travel to an endemic area was significantly associated with IgM (p=0.023) and IgG (p=0.041) positivity. A higher incidence of IgM (41.13%, 95% CI 35.55-46.71) and IgG (27.42%, 95% CI 22.36-32.48) was observed in urban areas than in rural areas (IgM 23%, 95% CI 18.34- 27.66, and IgG 13.41%, 95% CI 9.63-17.19). IgM (p=0.0005) and IgG (p=0.0007) positivity was significantly associated with area of residence. Symptoms including fever (p=0.007), headache (p=0.001), Skin rash (0.005), joint pain (0.004) and Fatigue were significantly linked to dengue fever. IgM and IgG antibodies were more frequently seen in the post-monsoon season (68.33%) than in the monsoon period (31.68%). The death ratio in the overall weighted prevalence was 2.19%. The results of the present cohort study of febrile subjects show that young people and males are more susceptible to dengue fever. Dengue infection was most prominent in the post-monsoon season, in urban areas, and in patients with a history of travel to an endemic locality. Furthermore seven deaths were found in our cohort study.