Households as foci for dengue transmission in highly urban Vietnam.

Katherine L Anders,Nguyen Van Vinh Chau,Huynh Thi Le Duyen,Nguyen Thanh Truong,Le Hong Nga,Nguyen Thi Van Thuy,Luong Thi Hue Tai,Cameron P Simmons,Nguyen Dac Tho,Duong Thi Hue Kien,Marcel Wolbers,Cao Thi Tam,Tran Van Ngoc,Vu Tuan Trung,Bridget Wills,Scott B Halstead

doi:10.1371/journal.pntd.0003528

Abstract

BackgroundDengue control programs commonly employ reactive insecticide spraying around houses of reported cases, with the assumption that most dengue virus (DENV) transmission occurs in the home. Focal household transmission has been demonstrated in rural settings, but it is unclear whether this holds true in dense and mobile urban populations. We conducted a prospective study of dengue clustering around households in highly urban Ho Chi Minh City, Vietnam.MethodsWe enrolled 71 index cases with suspected dengue (subsequently classified as 52 dengue cases and 19 non-dengue controls); each initiated the enrollment of a cluster of 25–35 household members and neighbors who were followed up over 14 days. Incident DENV infections in cluster participants were identified by RT-PCR, NS1-ELISA, and/or DENV-IgM/-IgG seroconversion, and recent infections by DENV-IgM positivity at baseline.Principal Findings/ConclusionsThere was no excess risk of DENV infection within dengue case clusters during the two-week follow-up, compared to control clusters, but the prevalence of recent DENV infection at baseline was two-fold higher in case clusters than controls (OR 2.3, 95%CI 1.0–5.1, p = 0.05). Prevalence of DENV infection in Aedes aegypti was similar in case and control houses, and low overall (1%). Our findings are broadly consistent with household clustering of dengue risk, but indicate that any clustering is at a short temporal scale rather than sustained chains of localized transmission. This suggests that reactive perifocal insecticide spraying may have a limited impact in this setting.

Highlights

Dengue represents a large and growing public health problem throughout the tropical and subtropical world, with nearly 100 million clinical cases estimated to occur annually [1]
Dengue control programs commonly employ reactive insecticide spraying around houses of reported cases, with the assumption that most dengue virus (DENV) transmission occurs in the home
Dengue is a viral disease transmitted between humans by Aedes aegypti mosquitoes

Summary

Introduction

Dengue represents a large and growing public health problem throughout the tropical and subtropical world, with nearly 100 million clinical cases estimated to occur annually [1]. With the notable exceptions of the Ae. aegypti eradication program in the Americas [4] and sustained periods of vector suppression in Singapore [5] and Cuba [6], the operational focus of Ae. aegypti control in endemic countries has been on reducing vector abundance to achieve a concomitant reduction in dengue transmission, rather than total elimination. The resources required to achieve broad and sustained suppression of Ae. aegypti exceed the national budgets of dengue control programs in many endemic countries, and a targeted reactive approach is commonly used based on perifocal insecticide spraying in and around the houses of reported dengue cases and their neighbors. Dengue control programs commonly employ reactive insecticide spraying around houses of reported cases, with the assumption that most dengue virus (DENV) transmission occurs in the home. We conducted a prospective study of dengue clustering around households in highly urban Ho Chi Minh City, Vietnam

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