title: Households as foci for dengue transmission in highly urban Vietnam.
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.
  
  
  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.
authors: Oxford University Clinical Research Unit-Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam; Centre for Tropical Medicine, University of Oxford, Oxford, United Kingdom; Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
authors: Katherine L
authors: KL
authors: Anders
authors: Preventive Medicine Centre, Ho Chi Minh City, Vietnam.
authors: Le Hong
authors: le H
authors: Nga
authors: Oxford University Clinical Research Unit-Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam.
authors: Nguyen Thi Van
authors: NT
authors: Thuy
authors: Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam.
authors: Tran Van
authors: TV
authors: Ngoc
authors: Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam.
authors: Cao Thi
authors: CT
authors: Tam
authors: Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam.
authors: Luong Thi Hue
authors: LT
authors: Tai
authors: Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam.
authors: Nguyen Thanh
authors: NT
authors: Truong
authors: Oxford University Clinical Research Unit-Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam.
authors: Huynh Thi Le
authors: HT
authors: Duyen
authors: Oxford University Clinical Research Unit-Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam.
authors: Vu Tuan
authors: VT
authors: Trung
authors: Oxford University Clinical Research Unit-Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam.
authors: Duong Thi Hue
authors: DT
authors: Kien
authors: Oxford University Clinical Research Unit-Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam; Centre for Tropical Medicine, University of Oxford, Oxford, United Kingdom.
authors: Marcel
authors: M
authors: Wolbers
authors: Oxford University Clinical Research Unit-Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam; Centre for Tropical Medicine, University of Oxford, Oxford, United Kingdom.
authors: Bridget
authors: B
authors: Wills
authors: Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam.
authors: Nguyen Van Vinh
authors: NV
authors: Chau
authors: Preventive Medicine Centre, Ho Chi Minh City, Vietnam.
authors: Nguyen Dac
authors: ND
authors: Tho
authors: Oxford University Clinical Research Unit-Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam; Centre for Tropical Medicine, University of Oxford, Oxford, United Kingdom; Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia.
authors: Cameron P
authors: CP
authors: Simmons
mesh_terms: D000293:Adolescent; D000328:Adult; D000330:Aedes / Q000821:virology*; D000818:Animals; D002648:Child; D002675:Child, Preschool; D002947:Cities; D016000:Cluster Analysis; D003715:Dengue / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission*; D003716:Dengue Virus / Q000145:classification; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007303:Insect Vectors / Q000821:virology*; D007306:Insecticides / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012424:Rural Population; D014505:Urban Population; D014744:Vietnam / Q000453:epidemiology; D055815:Young Adult
chemical_list: D007306:Insecticides