Risk factors of influenza transmission in households

Viboud, Cécile; Boëlle, Pierre‐Yves; Cauchemez, Simon; Lavenu, Audrey; Valleron, Alain‐Jacques; Flahault, Antoine; Carrat, Fabrice

doi:10.1016/j.ics.2004.01.013

Cited by 237 publications

(300 citation statements)

References 22 publications

(35 reference statements)

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“…We found that infected children were more infectious than infected adults for sH1N1, which was consistent with previous studies [22,30,31]. This might be explained by children having more frequent and intense contacts with other household members on average, compared with adults [32].…”

Section: Discussionsupporting

confidence: 92%

Influenza A Virus Shedding and Infectivity in Households

Tsang¹,

Cowling²,

Fang³

et al. 2015

J Infect Dis.

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103

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Background. Viral shedding is often considered to correlate with the infectivity of influenza, but the evidence for this is limited.Methods. In a detailed study of influenza virus transmission within households in 2008-2012, index case patients with confirmed influenza were identified in outpatient clinics, and we collected nose and throat swab specimens for testing by reverse-transcription polymerase chain reaction from all household members regardless of illness. We used individual-based hazard models to characterize the relationship between viral load (V ) and infectivity.Results. Assuming that infectivity was proportional to viral load V gave the worst fit, because it strongly overestimated the proportion of transmission occurring at symptom onset. Alternative models assuming that infectivity was proportional to a various functions of V provided better fits, although they all overestimated the proportion of transmission occurring >3 days after symptom onset. The best fitting model assumed that infectivity was proportion to V γ , with estimates of γ = 0.136 and γ = 0.156 for seasonal influenza A(H1N1) and A(H3N2) respectively.Conclusions. All the models we considered that used viral loads to approximate infectivity of a case imperfectly explained the timing of influenza secondary infections in households. Identification of more accurate correlates of infectivity will be important to inform control policies and disease modeling.

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Section: Discussionsupporting

confidence: 92%

Influenza A Virus Shedding and Infectivity in Households

Tsang¹,

Cowling²,

Fang³

et al. 2015

J Infect Dis.

Self Cite

103

View full text Add to dashboard Cite

show abstract

“…Unfortunately, there are very few experimental studies of human-to-human transmission; besides, existing studies are inconclusive and predate the discovery of the influenza virus [32,46,47]. Indirect evidence for influenza transmission between humans can nevertheless be found in observational studies in close contact settings, such as aeroplanes, hospitals, households, schools, and day-care centres [48][49][50][51][52][53]. In particular, influenza transmission is more intense in the household than in the community [51,54], while clinical trials have shown that treating index cases with antivirals reduces secondary transmission to household members [55].…”

Section: Discussionmentioning

confidence: 99%

Seasonal influenza in the United States, France, and Australia: transmission and prospects for control

2007

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SUMMARYRecurrent epidemics of influenza are observed seasonally around the world with considerable health and economic consequences. A key quantity for the control of infectious diseases is the reproduction number, which measures the transmissibility of a pathogen and determines the magnitude of public health interventions necessary to control epidemics. Here we applied a simple epidemic model to weekly indicators of influenza mortality to estimate the reproduction numbers of seasonal influenza epidemics spanning three decades in the United States, France, and Australia. We found similar distributions of reproduction number estimates in the three countries, with mean value 1.3 and important year-to-year variability (range 0.9-2.1). Estimates derived from two different mortality indicators (pneumonia and influenza excess deaths and influenza-specific deaths) were in close agreement for the United States (correlation = 0.61, P < 0.001) and France (correlation = 0.79, P < 0.001), but not Australia. Interestingly, high prevalence of A/H3N2 influenza viruses was associated with high transmission seasons (P = 0.006), while B viruses were more prevalent in low transmission seasons (P = 0.004). The current vaccination strategy targeted at people at highest risk of severe disease outcome is suboptimal because current vaccines are poorly immunogenic in these population groups. Our results suggest that interrupting transmission of seasonal influenza would require a relatively high vaccination coverage (> 60 %) in healthy individuals who respond well to vaccine, in addition to periodic re-vaccination due to evolving viral antigens and waning population immunity.

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“…Children up to 24 months are at highest risk of hospitalization and death 8 . Children played a major role in the influenza virus transmission and are the main introducers of influenza into households 9,10 .…”

Section: Ethical Considerationsmentioning

confidence: 99%

Surveillance of influenza A H1N1 2009 among school children during 2009 and 2010 in São Paulo, Brazil

Guatura

Watanabe

Camargo

et al. 2012

Rev. Soc. Bras. Med. Trop.

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Introduction: Influenza A H1N1 2009 is associated with a high morbidity rate among children around the world, including Brazil. This survey was conducted on samples of symptomatic children (≤ 12 years) to investigate the influenza virus as the etiological agent of respiratory infections in a day care school in a health facility during the first and second pandemic wave of H1N1 (2009)(2010) in São Paulo, Brazil. Methods: Influenza infections were determined by real-time PCR in 34% (47/137) of children with a median age of 5 years (8 months -12 years), from June to October 2009 and in 16% (14/85) of those with median age of 6 years (1-12 years), from March to November 2010. Results: In general, most positive cases (64%) occurred in children aged 5-12 years, this age group was significantly the most affected (39.8%, p = 0.001, OR = 8.3, CI 95% 1.9-36.9). Wheezing was reported by 31% (19/61) and dyspnea by 23% (14/61) of the studied patients. An outbreak of influenza H1N1 with an attack rate of 35.7% among children (median age 6 years) was documented in April 2010, before the vaccination campaign against the pandemic virus was extended for children up to 5 years in Brazil. Conclusions: Therefore, the study reinforces the recommendation to immunize school children to reduce the incidence of the disease.

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Risk factors of influenza transmission in households

Cited by 237 publications

References 22 publications

Influenza A Virus Shedding and Infectivity in Households

Influenza A Virus Shedding and Infectivity in Households

Seasonal influenza in the United States, France, and Australia: transmission and prospects for control

Surveillance of influenza A H1N1 2009 among school children during 2009 and 2010 in São Paulo, Brazil

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