Pandemic H1N1 virus transmission and shedding dynamics in index case households of a prospective Vietnamese cohort

Summary Objectives Influenza household transmission studies are required to guide prevention strategies but most passively recruit index cases that seek healthcare. We investigated A(H1N1)pdm09 transmission in a household-based cohort during 2009. Methods Health-workers visited 270 households weekly...

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Bibliographic Details
Published in:The Journal of infection 2014-06, Vol.68 (6), p.581-590
Main Authors: Thai, Pham Quang, Mai, Le Quynh, Welkers, Matthijs R.A, Hang, Nguyen Le Khanh, Thanh, Le Thi, Dung, Vu Tien Viet, Yen, Nguyen Thi Thu, Duong, Tran Nhu, Hoa, Le Nguyen Minh, Thoang, Dang Dinh, Trang, Hoang Thi Huyen, de Jong, Menno D, Wertheim, Heiman, Hien, Nguyen Tran, Horby, Peter, Fox, Annette
Format: Article
Language:English
Subjects:
Adolescent
Adult
Aged
Aged, 80 and over
Antibodies, Viral - blood
Antibody
Asian Continental Ancestry Group
Biological and medical sciences
Child
Child, Preschool
Cohort Studies
Family Characteristics
Female
General aspects
Genetic Variation
Household
Human viral diseases
Humans
Index
Infant
Infant, Newborn
Infectious Disease
Infectious diseases
Influenza
Influenza A Virus, H1N1 Subtype - isolation & purification
Influenza, Human - transmission
Influenza, Human - virology
Male
Medical sciences
Middle Aged
Pandemic
Prospective Studies
RNA, Viral - genetics
Secondary
Sequence Analysis, DNA
Serial interval
Shedding
Symptoms
Transmission
Viral diseases
Viral diseases of the respiratory system and ent viral diseases
Viral Load
Virus Shedding
Young Adult
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Summary:Summary Objectives Influenza household transmission studies are required to guide prevention strategies but most passively recruit index cases that seek healthcare. We investigated A(H1N1)pdm09 transmission in a household-based cohort during 2009. Methods Health-workers visited 270 households weekly, and collected swabs from influenza-like-illness cases. If A(H1N1)pdm09 was RT-PCR-confirmed, all household members had symptoms assessed and swabs collected daily for 10–15 days. Viral RNA was quantified and sequenced and serology performed on pre-pandemic sera. Results Index cases were detected in 20 households containing 81 people. 98.5% lacked A(H1N1)pdm09 neutralizing antibodies in pre-pandemic sera. Eleven (18.6%, 95% CI 10.7–30.4%) of 59 contacts were infected. Virus genetic diversity within households was negligible and less than between households. Index and secondary cases were distributed between mothers, daughters and sons, and had similar virus-RNA shedding and symptom dynamics. Fathers were rarely infected. Five secondary cases (45%) had no apparent symptoms and three shed virus before symptoms. Secondary infection was associated with index case wet cough (OR 1.56, 95% CI 1.22–1.99). Conclusions In this cohort of A(H1N1)pdm09 susceptible persons, virus sequencing was capable of discriminating household from community transmission. Household transmission involved mothers and children but rarely fathers. Asymptomatic or pre-symptomatic shedding was common.
ISSN:0163-4453
1532-2742
DOI:10.1016/j.jinf.2014.01.008