Dataset Information

Phylogeography of the spring and fall waves of the H1N1/09 pandemic influenza virus in the United States.

ABSTRACT: Spatial variation in the epidemiological patterns of successive waves of pandemic influenza virus in humans has been documented throughout the 20th century but never understood at a molecular level. However, the unprecedented intensity of sampling and whole-genome sequencing of the H1N1/09 pandemic virus now makes such an approach possible. To determine whether the spring and fall waves of the H1N1/09 influenza pandemic were associated with different epidemiological patterns, we undertook a large-scale phylogeographic analysis of viruses sampled from three localities in the United States. Analysis of genomic and epidemiological data reveals distinct spatial heterogeneities associated with the first pandemic wave, March to July 2009, in Houston, TX, Milwaukee, WI, and New York State. In Houston, no specific H1N1/09 viral lineage dominated during the spring of 2009, a period when little epidemiological activity was observed in Texas. In contrast, major pandemic outbreaks occurred at this time in Milwaukee and New York State, each dominated by a different viral lineage and resulting from strong founder effects. During the second pandemic wave, beginning in August 2009, all three U.S. localities were dominated by a single viral lineage, that which had been dominant in New York during wave 1. Hence, during this second phase of the pandemic, extensive viral migration and mixing diffused the spatially defined population structure that had characterized wave 1, amplifying the one viral lineage that had dominated early on in one of the world's largest international travel centers.

SUBMITTER: Nelson MI

PROVIDER: S-EPMC3020026 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Phylogeography of the spring and fall waves of the H1N1/09 pandemic influenza virus in the United States.

Nelson Martha I MI Tan Yi Y Ghedin Elodie E Wentworth David E DE St George Kirsten K Edelman Laurel L Beck Eric T ET Fan Jiang J Lam Tommy Tsan-Yuk TT Kumar Swati S Spiro David J DJ Simonsen Lone L Viboud Cecile C Holmes Edward C EC Henrickson Kelly J KJ Musser James M JM

Journal of virology 20101110 2

Spatial variation in the epidemiological patterns of successive waves of pandemic influenza virus in humans has been documented throughout the 20th century but never understood at a molecular level. However, the unprecedented intensity of sampling and whole-genome sequencing of the H1N1/09 pandemic virus now makes such an approach possible. To determine whether the spring and fall waves of the H1N1/09 influenza pandemic were associated with different epidemiological patterns, we undertook a larg ...[more]

PMID: 21068250

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Project description:BackgroundIn late spring 2009, concern was raised in Canada that prior vaccination with the 2008-09 trivalent inactivated influenza vaccine (TIV) was associated with increased risk of pandemic influenza A (H1N1) (pH1N1) illness. Several epidemiologic investigations were conducted through the summer to assess this putative association.Methods and findingsStudies included(1) test-negative case-control design based on Canada's sentinel vaccine effectiveness monitoring system in British Columbia, Alberta, Ontario, and Quebec; (2) conventional case-control design using population controls in Quebec; (3) test-negative case-control design in Ontario; and (4) prospective household transmission (cohort) study in Quebec. Logistic regression was used to estimate odds ratios for TIV effect on community- or hospital-based laboratory-confirmed seasonal or pH1N1 influenza cases compared to controls with restriction, stratification, and adjustment for covariates including combinations of age, sex, comorbidity, timeliness of medical visit, prior physician visits, and/or health care worker (HCW) status. For the prospective study risk ratios were computed. Based on the sentinel study of 672 cases and 857 controls, 2008-09 TIV was associated with statistically significant protection against seasonal influenza (odds ratio 0.44, 95% CI 0.33-0.59). In contrast, estimates from the sentinel and three other observational studies, involving a total of 1,226 laboratory-confirmed pH1N1 cases and 1,505 controls, indicated that prior receipt of 2008-09 TIV was associated with increased risk of medically attended pH1N1 illness during the spring-summer 2009, with estimated risk or odds ratios ranging from 1.4 to 2.5. Risk of pH1N1 hospitalization was not further increased among vaccinated people when comparing hospitalized to community cases.ConclusionsPrior receipt of 2008-09 TIV was associated with increased risk of medically attended pH1N1 illness during the spring-summer 2009 in Canada. The occurrence of bias (selection, information) or confounding cannot be ruled out. Further experimental and epidemiological assessment is warranted. Possible biological mechanisms and immunoepidemiologic implications are considered.

Project description:As of June 11, 2009, a total of 17,855 probable or confirmed cases of 2009 pandemic influenza A (H1N1) had been reported in the United States. Risk factors for transmission remain largely uncharacterized. We characterize the risk factors and describe the transmission of the virus within households.Probable and confirmed cases of infection with the 2009 H1N1 virus in the United States were reported to the Centers for Disease Control and Prevention with the use of a standardized case form. We investigated transmission of infection in 216 households--including 216 index patients and their 600 household contacts--in which the index patient was the first case patient and complete information on symptoms and age was available for all household members.An acute respiratory illness developed in 78 of 600 household contacts (13%). In 156 households (72% of the 216 households), an acute respiratory illness developed in none of the household contacts; in 46 households (21%), illness developed in one contact; and in 14 households (6%), illness developed in more than one contact. The proportion of household contacts in whom acute respiratory illness developed decreased with the size of the household, from 28% in two-member households to 9% in six-member households. Household contacts 18 years of age or younger were twice as susceptible as those 19 to 50 years of age (relative susceptibility, 1.96; Bayesian 95% credible interval, 1.05 to 3.78; P=0.005), and household contacts older than 50 years of age were less susceptible than those who were 19 to 50 years of age (relative susceptibility, 0.17; 95% credible interval, 0.02 to 0.92; P=0.03). Infectivity did not vary with age. The mean time between the onset of symptoms in a case patient and the onset of symptoms in the household contacts infected by that patient was 2.6 days (95% credible interval, 2.2 to 3.5).The transmissibility of the 2009 H1N1 influenza virus in households is lower than that seen in past pandemics. Most transmissions occur soon before or after the onset of symptoms in a case patient.

Project description:BackgroundPandemic influenza A(H1N1) (pH1N1) was first identified in North America in April 2009. Vaccination against pH1N1 commenced in the U.S. in October 2009 and continued through January 2010. The objective of this study was to evaluate the cost-effectiveness of pH1N1 vaccination.MethodologyA computer simulation model was developed to predict costs and health outcomes for a pH1N1 vaccination program using inactivated vaccine compared to no vaccination. Probabilities, costs and quality-of-life weights were derived from emerging primary data on pH1N1 infections in the US, published and unpublished data for seasonal and pH1N1 illnesses, supplemented by expert opinion. The modeled target population included hypothetical cohorts of persons aged 6 months and older stratified by age and risk. The analysis used a one-year time horizon for most endpoints but also includes longer-term costs and consequences of long-term sequelae deaths. A societal perspective was used. Indirect effects (i.e., herd effects) were not included in the primary analysis. The main endpoint was the incremental cost-effectiveness ratio in dollars per quality-adjusted life year (QALY) gained. Sensitivity analyses were conducted.ResultsFor vaccination initiated prior to the outbreak, pH1N1 vaccination was cost-saving for persons 6 months to 64 years under many assumptions. For those without high risk conditions, incremental cost-effectiveness ratios ranged from $8,000-$52,000/QALY depending on age and risk status. Results were sensitive to the number of vaccine doses needed, costs of vaccination, illness rates, and timing of vaccine delivery.ConclusionsVaccination for pH1N1 for children and working-age adults is cost-effective compared to other preventive health interventions under a wide range of scenarios. The economic evidence was consistent with target recommendations that were in place for pH1N1 vaccination. We also found that the delays in vaccine availability had a substantial impact on the cost-effectiveness of vaccination.

Dataset Information

Phylogeography of the spring and fall waves of the H1N1/09 pandemic influenza virus in the United States.

Publications

Phylogeography of the spring and fall waves of the H1N1/09 pandemic influenza virus in the United States.

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