Date Published: February 08, 2018
Publisher: The American Society of Tropical Medicine and Hygiene
Author(s): Duong Le Quyen, Nguyen Thanh Le, Cao Thi Van Anh, Nguyen Binh Nguyen, Dong Van Hoang, Jacqui L. Montgomery, Simon C. Kutcher, Nguyen Hoang Le, Nguyen Tran Hien, Duong Thi Hue Kien, Maia Rabaa, Scott L. O’Neill, Cameron P. Simmons, Dang Duc Anh, Katherine L. Anders.
Vietnam is endemic for dengue. We conducted a series of retrospective and prospective studies to characterize the epidemiology of dengue and population mobility patterns in Nha Trang city, Vietnam, with a view to rational design of trials of community-level interventions. A 10-year time series of dengue case notifications showed pronounced interannual variability, as well as spatial heterogeneity in ward-level dengue incidence (median annual coefficient of variation k = 0.47). Of 451 children aged 1–10 years enrolled in a cross-sectional serosurvey, almost one-third had evidence of a past dengue virus (DENV) infection, with older children more likely to have a multitypic response indicative of past exposure to ≥ 1 serotype. All four DENV serotypes were detected in hospitalized patients during 8 months of sampling in 2015. Mobility data collected from 1,000 children and young adults via prospective travel diaries showed that, although all ages spent approximately half of their daytime hours (5:00 am–9:00 pm) at home, younger age groups (≤ 14 years) spent a significantly greater proportion of their time within 500 m of home than older respondents. Together these findings inform the rational design of future trials of dengue preventive interventions in this setting by identifying 1) children < 7 years as an optimal target group for a flavivirus-naive serological cohort, 2) children and young adults as the predominant patient population for a study with a clinical end point of symptomatic dengue, and 3) substantial spatial and temporal variations in DENV transmission, with a consequent requirement for a trial to be large enough and of long enough duration to overcome this heterogeneity.
Dengue is a vector-borne tropical infectious disease that poses a public health challenge in over 100 countries.1 The disease is caused by dengue viruses (DENVs), of which there are four serotypes: DENV1–4.2,3 Dengue is an acute systemic febrile illness in which a small proportion of cases develop life-threatening complications.2–5 An estimated 50–100 million people worldwide suffer from a clinically apparent DENV infection each year,1,6 of an estimated 390 million (95% credible interval [CI]: 284–528 million) total annual DENV infections.1 DENVs are transmitted between humans by Aedes mosquitoes, with Aedes aegypti the primary vector and Aedes albopictus a secondary vector. The dramatic increase in global dengue incidence over the past half century has been linked to rapid urbanization, increased geographic distribution of vector species, and increasing human movement within and between areas.2,3
Here, we have demonstrated three critical features of dengue in Nha Trang city relevant for planning field trials of interventions to reduce arbovirus transmission. First, there is pronounced temporal and spatial heterogeneity in dengue incidence across the city. Second, children and young adults are the populations most at risk of infection and disease. Third, all four DENV serotypes cocirculate in Nha Trang within a single season.