A prospective case–control study was conducted in urban districts in Hanoi, northern Vietnam to evaluate the effect of migration on the risk of hospitalisation for dengue in a Vietnamese urban population. We enrolled laboratory-confirmed dengue patients aged >18 years who were hospitalised in local hospitals in November and December 2010. Four neighbourhood-matched controls for each case were recruited within a week of hospitalisation. Sociodemographic data were collected by interviews, and the number of immature and adult mosquitoes within household premises was counted by entomological survey. Matched-pair analyses were conducted using conditional logistic regression models. Among 43 cases and 168 controls, 84% and 83% were migrants from rural areas, respectively. Although statistical significance was marginal, recent migration (residing in study area for <5 years) independently increased the risk of hospitalisation for dengue compared with inhabitants after controlling for potential confounders (adjusted odds ratio [aOR] = 3.78; 95% confidence interval [CI] = 0.99–14.27), whereas longer-term migration (residing in study area for >6 years) did not change the risk (aOR = 1.1; 95% CI = 0.30–4.05). Younger age (18–34 years) (aOR = 7.26; 95% CI = 2.39–22.06) and higher adult Aedes aegypti infestation level within household premises (aOR = 9.25; 95% CI = 1.68–51.09) were also independently associated with hospitalisation for dengue. Recent migration from rural areas seems to increase the risk of hospitalisation for dengue in urban populations in endemic areas. Further research including cohort study should be done to confirm the impact of migration on the risk of dengue in urban areas.

A population-based cohort study on pediatric infectious diseases was established at Khanh Hoa Province, central Vietnam in 2006, to determine the etiology and risk factors for severe pediatric infectious diseases (SPID) such as acute respiratory infection (ARI), diarrhea and dengue which are the major causes of under 5 mortality. A population census survey was conducted in Nha-Trang and Ninh-Hoa to collect demographic, social-behavioral data and disease burden on SPID. The study site covered a population of 353,525 residing in 75,826 households with 24,781 children less than 5 years. Hospital databases from two hospitals covering the region were obtained. Linking the census and hospital databases, we were able to investigate on a variety of SPID such as environmental tobacco smoking exposure and increased risked of pediatric pneumonia hospitalization, population density, water supply and risk of dengue fever and animal livestock and risk of hospitalized diarrhea. To determine incidence, viral etiology and risk factors for pediatric ARI/pneumonia, we setup a population based prospective hospitalized Pediatric ARI surveillance at Khanh Hoa General Hospital, Nha-Trang in February 2007. The study has revealed RSV, rhinovirus and influenza A as major viral pathogens, role of multiple viral infection and its interaction with bacteria in the development of pneumonia. In addition, we are also conducting a birth cohort study to investigate the incidence of congenital infection and its impact on physical-neurological development, and role of host genetic polymorphism on SPID hospitalization in Vietnam. Population mobility, high cost of regular census update and low mortality are the challenges.

A population-based cohort study on pediatric infectious diseases was established at Khanh Hoa Province, central Vietnam in 2006, to determine the etiology and risk factors for severe pediatric infectious diseases (SPID) such as acute respiratory infection (ARI), diarrhea and dengue which are the major causes of under 5 mortality. A population census survey was conducted in Nha-Trang and Ninh-Hoa to collect demographic, social-behavioral data and disease burden on SPID. The study site covered a population of 353,525 residing in 75,826 households with 24,781 children less than 5 years. Hospital databases from two hospitals covering the region were obtained. Linking the census and hospital databases, we were able to investigate on a variety of SPID such as environmental tobacco smoking exposure and increased risked of pediatric pneumonia hospitalization, population density, water supply and risk of dengue fever and animal livestock and risk of hospitalized diarrhea. To determine incidence, viral etiology and risk factors for pediatric ARI/pneumonia, we setup a population based prospective hospitalized Pediatric ARI surveillance at Khanh Hoa General Hospital, Nha-Trang in February 2007. The study has revealed RSV, rhinovirus and influenza A as major viral pathogens, role of multiple viral infection and its interaction with bacteria in the development of pneumonia. In addition, we are also conducting a birth cohort study to investigate the incidence of congenital infection and its impact on physical-neurological development, and role of host genetic polymorphism on SPID hospitalization in Vietnam. Population mobility, high cost of regular census update and low mortality are the challenges.