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- Title
Households as Foci for Dengue Transmission in Highly Urban Vietnam.
- Authors
Anders, Katherine L.; Nga, Le Hong; Thuy, Nguyen Thi Van; Ngoc, Tran Van; Tam, Cao Thi; Tai, Luong Thi Hue; Truong, Nguyen Thanh; Duyen, Huynh Thi Le; Trung, Vu Tuan; Kien, Duong Thi Hue; Wolbers, Marcel; Wills, Bridget; Chau, Nguyen Van Vinh; Tho, Nguyen Dac; Simmons, Cameron P.
- Abstract
Background: 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. 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. Methods: We 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/Conclusions: There 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. Author Summary: Dengue is a viral disease transmitted between humans by Aedes aegypti mosquitoes. It is an increasing health problem in tropical regions, with no vaccine or drug available. The main approach used for dengue prevention and control is reducing mosquito numbers, which is commonly done by spraying insecticide around the houses of reported dengue cases and their neighbors. This assumes that mosquito populations around the home contribute to onwards transmission of dengue to other people living near the identified case, and that by reducing these populations further infections can be prevented. A previous study in rural villages in Thailand showed that dengue infections did cluster near the house of a case, but it is not clear whether this would also be the case in a densely-populated urban setting like Ho Chi Minh City. In this study, we show that people living close to a dengue case in HCMC were in fact no more likely to be infected with dengue over a two week period than controls who did not live near a dengue case, although they were two times more likely to have evidence of a recent dengue infection at enrollment. This suggests that dengue risk might cluster around households in this setting, but that responsive insecticide spraying around the homes of reported cases is unlikely to prevent many additional infections.
- Subjects
HO Chi Minh City (Vietnam); VIETNAM; THAILAND; DENGUE hemorrhagic fever; DENGUE; DENGUE viruses; VIRUS diseases; AEDES aegypti; HOUSEHOLDS
- Publication
PLoS Neglected Tropical Diseases, 2015, Vol 9, Issue 2, p1
- ISSN
1935-2727
- Publication type
Article
- DOI
10.1371/journal.pntd.0003528