Dengue seroprevalence, seroconversion and risk factors in Dhaka, Bangladesh

<div><p>Background</p><p>Dengue virus (DENV) activity has been reported in Dhaka, Bangladesh since the early 1960s with the greatest burden of dengue fever and dengue hemorrhagic fever cases observed in 2000. Since this time, the intensity of dengue activity has varied from year to year, and its determining factors remained relatively unknown. In light of such gaps in knowledge, the main objectives of this study were to determine the magnitude of seroprevalence and seroconversion among the surveyed population, and establish the individual/household level risk factors for the presence of DENV antibodies among all age groups of target populations in the city of Dhaka.</p><p>Methodology/Principal findings</p><p>Considering the lack of fine scale investigations on the factors driving dengue activity in Bangladesh, a prospective cohort study involving serological surveys was undertaken with participant interviews and blood donation across the city of Dhaka in 2012. Study participants were recruited from 12 of 90 wards and blood samples were collected during both the pre-monsoon (n = 1125) and post-monsoon (n = 600) seasons of 2012. The findings revealed that the seroprevalence in all pre-monsoon samples was 80.0% (900/1125) while the seropositivity in the pre-monsoon samples that had paired post-monsoon samples was 83.3% (503/600). Of the 97 paired samples that were negative at the pre-monsoon time point, 56 were positive at the post-monsoon time point. This resulted in a seroprevalence of 93.2% (559/600) among individuals tested during the post-monsoon period. Seroprevalence trended higher with age with children exhibiting a lower seropositivity as compared to adults. Results from this study also indicated that DENV strains were the only flaviviruses circulating in Dhaka in 2012. A multivariate analysis revealed that age, possession of indoor potted plants, and types of mosquito control measures were significant factors associated with DENV seroprevalence; while attendance in public/mass gatherings, and use of mosquito control measures were significantly associated with DENV seroconversion after adjusting for all other variables.</p><p>Conclusions/Significance</p><p>Our study suggests that there is a high level of endemic dengue virus circulation in the city of Dhaka which has resulted in significant DENV seroprevalence among its residents. Seropositivity increased with age, however, a substantial proportion of children are at risk for DENV infections. Our serological analysis also documents considerable DENV seroconversion among study participants which indicates that a large proportion of the population in the city of Dhaka were newly exposed to DENV during the study period (pre-and post-monsoon 2012). High levels of seroconversion suggest that there was an intense circulation of DENV in 2012 and this may have resulted in a significant risk for viral associated illness. Findings of our study further indicated that home-based interventions, such as removing indoor potted plants and increased bed net use, in addition to vector control measures in public parks, would reduce exposure to DENV and further decrease risk of viral associated disease.</p></div

Number of counts (sample) and cumulative percentage of seropositive (IgG) cases among the children (≤12 years) by year, 2012 pre-monsoon serosurvey.

<p>Number of counts (sample) and cumulative percentage of seropositive (IgG) cases among the children (≤12 years) by year, 2012 pre-monsoon serosurvey.</p

Identifying cholera "hotspots" in Uganda: An analysis of cholera surveillance data from 2011 to 2016

<div><p>Background</p><p>Despite advance in science and technology for prevention, detection and treatment of cholera, this infectious disease remains a major public health problem in many countries in sub-Saharan Africa, Uganda inclusive. The aim of this study was to identify cholera hotspots in Uganda to guide the development of a roadmap for prevention, control and elimination of cholera in the country.</p><p>Methodology/Principle findings</p><p>We obtained district level confirmed cholera outbreak data from 2011 to 2016 from the Ministry of Health, Uganda. Population and rainfall data were obtained from the Uganda Bureau of Statistics, and water, sanitation and hygiene data from the Ministry of Water and Environment. A spatial scan test was performed to identify the significantly high risk clusters. Cholera hotspots were defined as districts whose center fell within a significantly high risk cluster or where a significantly high risk cluster was completely superimposed onto a district. A zero-inflated negative binomial regression model was employed to identify the district level risk factors for cholera. In total 11,030 cases of cholera were reported during the 6-year period. 37(33%) of 112 districts reported cholera outbreaks in one of the six years, and 20 (18%) districts experienced cholera at least twice in those years. We identified 22 districts as high risk for cholera, of which 13 were near a border of Democratic Republic of Congo (DRC), while 9 districts were near a border of Kenya. The relative risk of having cholera inside the high-risk districts (hotspots) were 2 to 22 times higher than elsewhere in the country. In total, 7 million people were within cholera hotspots. The negative binomial component of the ZINB model shows people living near a lake or the Nile river were at increased risk for cholera (incidence rate ratio, IRR = 0.98, 95% CI: 0.97 to 0.99, p < .01); people living near the border of DRC/Kenya or higher incidence rate in the neighboring districts were increased risk for cholera in a district (IRR = 0.99, 95% CI: 0.98 to 1.00, p = .02 and IRR = 1.02, 95% CI: 1.01 to 1.03, p < .01, respectively). The zero inflated component of the ZINB model yielded shorter distance to Kenya or DRC border, higher incidence rate in the neighboring districts, and higher annual rainfall in the district were associated with the risk of having cholera in the district.</p><p>Conclusions/significance</p><p>The study identified cholera hotspots during the period 2011–2016. The people located near the international borders, internationally shared lakes and river Nile were at higher risk for cholera outbreaks than elsewhere in the country. Targeting cholera interventions to these locations could prevent and ultimately eliminate cholera in Uganda.</p></div

Univariate association between seroprevalence (IgG) of dengue and selected explanatory variables during the 2012 pre-monsoon serosurvey.

<p>Univariate association between seroprevalence (IgG) of dengue and selected explanatory variables during the 2012 pre-monsoon serosurvey.</p

Ornamental potted plants that hold water in containers are common in living rooms of middle and high SES households.

<p>Ornamental potted plants that hold water in containers are common in living rooms of middle and high SES households.</p

Proportion of individuals in which antibodies to dengue were detected in paired blood samples collected during the pre- and post-monsoon seasons in 2012, Dhaka, Bangladesh.

<p>Proportion of individuals in which antibodies to dengue were detected in paired blood samples collected during the pre- and post-monsoon seasons in 2012, Dhaka, Bangladesh.</p

Receiver Operating Characteristic (ROC) curve for the association between seroprevalence and the explanatory variables, 2012 pre-monsoon serosurvey.

<p>Receiver Operating Characteristic (ROC) curve for the association between seroprevalence and the explanatory variables, 2012 pre-monsoon serosurvey.</p

Number of counts (sample) and percentage of seropositive (IgG) cases by age groups (all ages), 2012 pre-monsoon serosurvey.

<p>Number of counts (sample) and percentage of seropositive (IgG) cases by age groups (all ages), 2012 pre-monsoon serosurvey.</p

Estimated odds ratios (OR) for the multilevel analysis of the association between seroprevalence and selected explanatory variables from univariate analysis of 2012 pre-monsoon serosurveys data.

<p>Estimated odds ratios (OR) for the multilevel analysis of the association between seroprevalence and selected explanatory variables from univariate analysis of 2012 pre-monsoon serosurveys data.</p

Estimated odds ratios (OR) for the multilevel analysis of the association between seroconversion of dengue and selected explanatory variables, 2012 pre- and post-monsoon serosurveys.

<p>Estimated odds ratios (OR) for the multilevel analysis of the association between seroconversion of dengue and selected explanatory variables, 2012 pre- and post-monsoon serosurveys.</p