751
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Novel swine-origin influenza A virus in humans: another pandemic knocking at the door. Med Microbiol Immunol 2009; 198:175-83. [PMID: 19543913 DOI: 10.1007/s00430-009-0118-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Indexed: 12/27/2022]
Abstract
Influenza A viruses represent a continuous pandemic threat. In April 2009, a novel influenza A virus, the so-called swine-origin influenza A (H1N1) virus (S-OIV), was identified in Mexico. Although S-OIV originates from triple-reassortant swine influenza A (H1) that has been circulating in North American pig herds since the end of the 1990s, S-OIV is readily transmitted between humans but is not epidemic in pigs. After its discovery, S-OIV rapidly spread throughout the world within few weeks. In this review, we sum up the current situation and put it into the context of the current state of knowledge of influenza and influenza pandemics. Some indications suggest that a pandemic may be mild but even "mild" pandemics can result in millions of deaths. However, no reasonable forecasts how this pandemic may develop can be made at this time. Despite stockpiling by many countries and WHO, antiviral drugs will be limited in case of pandemic and resistances may emerge. Effective vaccines are regarded to be crucial for the control of influenza pandemics. However, production capacities are restricted and development/production of a S-OIV vaccine will interfere with manufacturing of seasonal influenza vaccines. The authors are convinced that S-OIV should be taken seriously as pandemic threat and underestimation of the menace by S-OIV to be by far more dangerous than its overestimation.
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752
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Dawood FS, Jain S, Finelli L, Shaw MW, Lindstrom S, Garten RJ, Gubareva LV, Xu X, Bridges CB, Uyeki TM. Emergence of a novel swine-origin influenza A (H1N1) virus in humans. N Engl J Med 2009; 360:2605-15. [PMID: 19423869 DOI: 10.1056/nejmoa0903810] [Citation(s) in RCA: 2187] [Impact Index Per Article: 145.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
BACKGROUND On April 15 and April 17, 2009, novel swine-origin influenza A (H1N1) virus (S-OIV) was identified in specimens obtained from two epidemiologically unlinked patients in the United States. The same strain of the virus was identified in Mexico, Canada, and elsewhere. We describe 642 confirmed cases of human S-OIV infection identified from the rapidly evolving U.S. outbreak. METHODS Enhanced surveillance was implemented in the United States for human infection with influenza A viruses that could not be subtyped. Specimens were sent to the Centers for Disease Control and Prevention for real-time reverse-transcriptase-polymerase-chain-reaction confirmatory testing for S-OIV. RESULTS From April 15 through May 5, a total of 642 confirmed cases of S-OIV infection were identified in 41 states. The ages of patients ranged from 3 months to 81 years; 60% of patients were 18 years of age or younger. Of patients with available data, 18% had recently traveled to Mexico, and 16% were identified from school outbreaks of S-OIV infection. The most common presenting symptoms were fever (94% of patients), cough (92%), and sore throat (66%); 25% of patients had diarrhea, and 25% had vomiting. Of the 399 patients for whom hospitalization status was known, 36 (9%) required hospitalization. Of 22 hospitalized patients with available data, 12 had characteristics that conferred an increased risk of severe seasonal influenza, 11 had pneumonia, 8 required admission to an intensive care unit, 4 had respiratory failure, and 2 died. The S-OIV was determined to have a unique genome composition that had not been identified previously. CONCLUSIONS A novel swine-origin influenza A virus was identified as the cause of outbreaks of febrile respiratory infection ranging from self-limited to severe illness. It is likely that the number of confirmed cases underestimates the number of cases that have occurred.
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753
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Zuk T, Rakowski F, Radomski JP. A model of influenza virus spread as a function of temperature and humidity. Comput Biol Chem 2009; 33:176-80. [PMID: 19266626 DOI: 10.1016/j.compbiolchem.2008.12.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The influence that atmospheric conditions might have on the efficiency of the spread of influenza virus is important for epidemiological and evolutionary research. However, it has not been satisfactorily recognized and quantified so far. Here we provide a statistical model of influenza transmission between individuals. It has been derived from the results of recent experiments, which involved infecting guinea pigs with influenza at various temperatures and relative air humidity levels. The wide range of transmission rates in those experiments reflects the ensemble-independent phenomena. The correlation between most of our simulations and the experimental results is satisfactory. For several different conditions, we obtained transmissibility values which seem to be sufficiently accurate to provide partial input for an intended large-scale epidemiological study in the near future.
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Affiliation(s)
- Tomasz Zuk
- Interdisciplinary Center for Mathematical and Computational Modeling, University of Warsaw, Pawińskiego 5A, Bldg D, 02-106 Warsaw, Poland
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754
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Wood J, McCaw J, Becker N, Nolan T, MacIntyre CR. Optimal dosing and dynamic distribution of vaccines in an influenza pandemic. Am J Epidemiol 2009; 169:1517-24. [PMID: 19395691 PMCID: PMC2691801 DOI: 10.1093/aje/kwp072] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Limited production capacity and delays inherent in vaccine development are major hurdles to the widespread use of vaccines to mitigate the effects of a new influenza pandemic. Antigen-sparing vaccines have the most potential to increase population coverage but may be less efficacious. The authors explored this trade-off by applying simple models of influenza transmission and dose response to recent clinical trial data. In this paper, these data are used to illustrate an approach to comparing vaccines on the basis of antigen supply and inferred efficacy. The effects of delays in matched vaccine availability and seroconversion on epidemic size during pandemic phase 6 were also studied. The authors infer from trial data that population benefits stem from the use of low-antigen vaccines. Delayed availability of a matched vaccine could be partially alleviated by using a 1-dose vaccination program with increased coverage and reduced time to full protection. Although less immunogenic, an overall attack rate of up to 6% lower than a 2-dose program could be achieved. However, if prevalence at vaccination is above 1%, effectiveness is much reduced, emphasizing the need for other control measures.
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Affiliation(s)
- James Wood
- School of Public Health and Community Medicine, University of New South Wales, New South Wales, Australia.
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755
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Mubareka S, Lowen AC, Steel J, Coates AL, García-Sastre A, Palese P. Transmission of influenza virus via aerosols and fomites in the guinea pig model. J Infect Dis 2009; 199:858-65. [PMID: 19434931 PMCID: PMC4180291 DOI: 10.1086/597073] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Limited data on the relative contributions of different routes of transmission for influenza virus are available. Person-to-person transmission is central to seasonal and pandemic spread; nevertheless, the modes of spread are a matter of ongoing debate. Resolution of this discussion is paramount to the development of effective control measures in health care and community settings. Using the guinea pig model, we demonstrated that transmission of influenza A/Panama/2007/1999 (H3N2) virus through the air is efficient, compared with spread through contaminated environmental surfaces (fomites). We also examined the aerosol transmission efficiencies of 2 human influenza virus A strains and found that A/Panama/2007/1999 influenza virus transmitted more efficiently than A/Texas/36/1991 (H1N1) virus in our model. The data provide new and much-needed insights into the modes of influenza virus spread and strain-specific differences in the efficiency of transmission
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Affiliation(s)
- Samira Mubareka
- Department of Microbiology, Mount Sinai School of Medicine, New York, New York 10029, USA
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756
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Machado AA. Infecção pelo vírus Influenza A (H1N1) de origem suína: como reconhecer, diagnosticar e prevenir. J Bras Pneumol 2009; 35:464-9. [DOI: 10.1590/s1806-37132009000500013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Accepted: 05/12/2009] [Indexed: 11/22/2022] Open
Abstract
Em março de 2009, houve o início de uma epidemia de gripe no México que, em pouco tempo, levou ao surgimento de casos semelhantes em outros países, alertando as autoridades sanitárias para o risco de uma pandemia. Neste artigo, descrevemos os principais sinais e sintomas da infecção pelo vírus Influenza A (H1N1) de origem suína, as medidas a serem tomadas para os casos suspeitos ou confirmados e como proceder em relação aos contactantes. Comentamos também quais drogas são utilizadas para o tratamento e profilaxia.
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757
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Patrozou E, Mermel LA. Does influenza transmission occur from asymptomatic infection or prior to symptom onset? Public Health Rep 2009; 124:193-6. [PMID: 19320359 DOI: 10.1177/003335490912400205] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
A better understanding of transmission dynamics is essential in influenza pandemic planning. If a substantial proportion of transmissions were to occur during the presymptomatic phase or from asymptomatic individuals, then infection control measures such as contact tracing and quarantine of exposures would be of limited value. Infectiousness has been inferred based on the presence of influenza in the upper respiratory tract rather than from transmission experiments. Although asymptomatic individuals may shed influenza virus, studies have not determined if such people effectively transmit influenza. We performed a systematic review of published studies describing the relationship between viral shedding and disease transmission. Based on the available literature, we found that there is scant, if any, evidence that asymptomatic or presymptomatic individuals play an important role in influenza transmission. As such, recent articles concerning pandemic planning, some using transmission modeling, may have overestimated the effect of presymptomatic or asymptomatic influenza transmission. More definitive transmission studies are sorely needed.
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Affiliation(s)
- Eleni Patrozou
- Division of Infectious Diseases, Department of Medicine, Warren Alpert Medical School of Brown University, Providence, RI, USA
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758
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Harper SA, Bradley JS, Englund JA, File TM, Gravenstein S, Hayden FG, McGeer AJ, Neuzil KM, Pavia AT, Tapper ML, Uyeki TM, Zimmerman RK. Seasonal influenza in adults and children--diagnosis, treatment, chemoprophylaxis, and institutional outbreak management: clinical practice guidelines of the Infectious Diseases Society of America. Clin Infect Dis 2009; 48:1003-32. [PMID: 19281331 PMCID: PMC7107965 DOI: 10.1086/598513] [Citation(s) in RCA: 495] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Guidelines for the treatment of persons with influenza virus infection were prepared by an Expert Panel of the Infectious Diseases Society of America. The evidence-based guidelines encompass diagnostic issues, treatment and chemoprophylaxis with antiviral medications, and issues related to institutional outbreak management for seasonal (interpandemic) influenza. They are intended for use by physicians in all medical specialties with direct patient care, because influenza virus infection is common in communities during influenza season and may be encountered by practitioners caring for a wide variety of patients.
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Affiliation(s)
- Scott A Harper
- Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
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759
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Lowen AC, Steel J, Mubareka S, Carnero E, García-Sastre A, Palese P. Blocking interhost transmission of influenza virus by vaccination in the guinea pig model. J Virol 2009; 83:2803-18. [PMID: 19153237 PMCID: PMC2655561 DOI: 10.1128/jvi.02424-08] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2008] [Accepted: 01/09/2009] [Indexed: 11/20/2022] Open
Abstract
Interventions aimed at preventing viral spread have the potential to effectively control influenza virus in all age groups, thereby reducing the burden of influenza illness. For this reason, we have examined the efficacy of vaccination in blocking the transmission of influenza viruses between guinea pigs. Three modes of immunization were compared: (i) natural infection; (ii) intramuscular administration of whole, inactivated influenza virus in 2 doses; and (iii) intranasal inoculation with live attenuated influenza virus in 2 doses. The ability of each immunization method to block the spread of a homologous (A/Panama/2007/99) H3N2 subtype and a heterologous (A/Wisconsin/67/05) H3N2 subtype influenza virus was tested. We found that previous infection through a natural route provided sterilizing immunity against both homologous and heterologous challenges; thus, no transmission to or from previously infected animals was observed. Vaccination with an inactivated influenza virus vaccine, in contrast, did not prevent guinea pigs from becoming infected upon challenge with either virus. Thus, both intranasal inoculation and exposure to an acutely infected guinea pig led to the infection of vaccinated animals. Vaccination with inactivated virus did, however, reduce viral load upon challenge and decrease the number of secondary transmission events from vaccinated animals to naïve cage mates. Vaccination with a live attenuated virus was found to be more efficacious than vaccination with inactivated virus, resulting in sterilizing immunity against homologous challenge and full protection against the transmission of the homologous and heterologous viruses to naïve contacts. In conclusion, we have shown that the guinea pig model can be used to test influenza virus vaccines and that the efficiency of transmission is a valuable readout when vaccine efficacy is evaluated.
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Affiliation(s)
- Anice C Lowen
- Department of Microbiology, Mount Sinai School of Medicine, 1 Gustave Levy Pl., New York, NY 10029-6574, USA
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760
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Influenza virus shedding—Excretion patterns and effects of antiviral treatment. J Clin Virol 2009; 44:255-61. [DOI: 10.1016/j.jcv.2009.01.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Revised: 01/16/2009] [Accepted: 01/21/2009] [Indexed: 11/24/2022]
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761
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Nishiura H, Wilson N, Baker MG. Quarantine for pandemic influenza control at the borders of small island nations. BMC Infect Dis 2009; 9:27. [PMID: 19284571 PMCID: PMC2670846 DOI: 10.1186/1471-2334-9-27] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2008] [Accepted: 03/11/2009] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND Although border quarantine is included in many influenza pandemic plans, detailed guidelines have yet to be formulated, including considerations for the optimal quarantine length. Motivated by the situation of small island nations, which will probably experience the introduction of pandemic influenza via just one airport, we examined the potential effectiveness of quarantine as a border control measure. METHODS Analysing the detailed epidemiologic characteristics of influenza, the effectiveness of quarantine at the borders of islands was modelled as the relative reduction of the risk of releasing infectious individuals into the community, explicitly accounting for the presence of asymptomatic infected individuals. The potential benefit of adding the use of rapid diagnostic testing to the quarantine process was also considered. RESULTS We predict that 95% and 99% effectiveness in preventing the release of infectious individuals into the community could be achieved with quarantine periods of longer than 4.7 and 8.6 days, respectively. If rapid diagnostic testing is combined with quarantine, the lengths of quarantine to achieve 95% and 99% effectiveness could be shortened to 2.6 and 5.7 days, respectively. Sensitivity analysis revealed that quarantine alone for 8.7 days or quarantine for 5.7 days combined with using rapid diagnostic testing could prevent secondary transmissions caused by the released infectious individuals for a plausible range of prevalence at the source country (up to 10%) and for a modest number of incoming travellers (up to 8000 individuals). CONCLUSION Quarantine at the borders of island nations could contribute substantially to preventing the arrival of pandemic influenza (or at least delaying the arrival date). For small island nations we recommend consideration of quarantine alone for 9 days or quarantine for 6 days combined with using rapid diagnostic testing (if available).
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Affiliation(s)
- Hiroshi Nishiura
- Theoretical Epidemiology, University of Utrecht, 3584 CL Utrecht, the Netherlands
| | - Nick Wilson
- Pandemic Influenza Research Group, University of Otago, Wellington, New Zealand
| | - Michael G Baker
- Pandemic Influenza Research Group, University of Otago, Wellington, New Zealand
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762
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Bouma A, Claassen I, Natih K, Klinkenberg D, Donnelly CA, Koch G, van Boven M. Estimation of transmission parameters of H5N1 avian influenza virus in chickens. PLoS Pathog 2009; 5:e1000281. [PMID: 19180190 PMCID: PMC2627927 DOI: 10.1371/journal.ppat.1000281] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Accepted: 12/26/2008] [Indexed: 11/25/2022] Open
Abstract
Despite considerable research efforts, little is yet known about key epidemiological parameters of H5N1 highly pathogenic influenza viruses in their avian hosts. Here we show how these parameters can be estimated using a limited number of birds in experimental transmission studies. Our quantitative estimates, based on Bayesian methods of inference, reveal that (i) the period of latency of H5N1 influenza virus in unvaccinated chickens is short (mean: 0.24 days; 95% credible interval: 0.099–0.48 days); (ii) the infectious period of H5N1 virus in unvaccinated chickens is approximately 2 days (mean: 2.1 days; 95%CI: 1.8–2.3 days); (iii) the reproduction number of H5N1 virus in unvaccinated chickens need not be high (mean: 1.6; 95%CI: 0.90–2.5), although the virus is expected to spread rapidly because it has a short generation interval in unvaccinated chickens (mean: 1.3 days; 95%CI: 1.0–1.5 days); and (iv) vaccination with genetically and antigenically distant H5N2 vaccines can effectively halt transmission. Simulations based on the estimated parameters indicate that herd immunity may be obtained if at least 80% of chickens in a flock are vaccinated. We discuss the implications for the control of H5N1 avian influenza virus in areas where it is endemic. Outbreaks of highly pathogenic H5N1 avian influenza in poultry first occurred in China in 1996. Since that time, the virus has become endemic in Asia, and has been the cause of outbreaks in Africa and Europe. Although many aspects of H5N1 virus biology have been studied in detail, surprisingly little is known about the key epidemiological parameters of the virus in its avian hosts (the length of time from infection until a bird becomes infectious, the duration of infectiousness, how many birds each infectious bird will infect). In this paper we show, using experimental transmission studies with unvaccinated and vaccinated chickens, that H5N1 avian influenza induces a short duration of infectiousness (∼2 days) and a very short period of time from infection until infectiousness (∼0.25 day) in unvaccinated chickens. Furthermore, while transmission was efficient among unvaccinated birds, no bird-to-bird transmission was observed in vaccinated chickens. Our results indicate that it may be difficult to curb outbreaks by vaccination after an introduction in a flock has been detected. On the other hand, preventive vaccination could be effective in preventing virus introductions and limiting the size of outbreaks.
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Affiliation(s)
- Annemarie Bouma
- Faculty of Veterinary Medicine, Utrecht University, The Netherlands
| | - Ivo Claassen
- Central Veterinary Institute, Wageningen University and Research Centre, The Netherlands
| | - Ketut Natih
- National Veterinary Drug Assay Laboratory, Bogor, Indonesia
| | - Don Klinkenberg
- Faculty of Veterinary Medicine, Utrecht University, The Netherlands
| | - Christl A. Donnelly
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Guus Koch
- Central Veterinary Institute, Wageningen University and Research Centre, The Netherlands
| | - Michiel van Boven
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, The Netherlands
- * E-mail:
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763
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764
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Affiliation(s)
- Jina Lee
- Department of Pediatrics, Seoul National University Children's Hospital, Seoul, Korea
| | - Hoan Jong Lee
- Department of Pediatrics, Seoul National University Children's Hospital, Seoul, Korea
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765
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Sinha M. Swine flu. J Infect Public Health 2009; 2:157-66. [DOI: 10.1016/j.jiph.2009.08.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Revised: 08/20/2009] [Accepted: 08/27/2009] [Indexed: 10/20/2022] Open
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766
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Kim HL, Jeon HH, Kim M, Kang CH, Park KH. Laboratory Confirmatory Rate of Pandemic Influenza (H1N1 2009) Virus in Korean Households with Index Case. Infect Chemother 2009. [DOI: 10.3947/ic.2010.42.2.82] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
| | | | - Min Kim
- Armed Forces Seoul Hospital, Seoul, Korea
| | | | - Kyung-Hwa Park
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, Korea
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767
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Milne GJ, Kelso JK, Kelly HA, Huband ST, McVernon J. A small community model for the transmission of infectious diseases: comparison of school closure as an intervention in individual-based models of an influenza pandemic. PLoS One 2008; 3:e4005. [PMID: 19104659 PMCID: PMC2602849 DOI: 10.1371/journal.pone.0004005] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Accepted: 11/20/2008] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND In the absence of other evidence, modelling has been used extensively to help policy makers plan for a potential future influenza pandemic. METHOD We have constructed an individual based model of a small community in the developed world with detail down to exact household structure obtained from census collection datasets and precise simulation of household demographics, movement within the community and individual contact patterns. We modelled the spread of pandemic influenza in this community and the effect on daily and final attack rates of four social distancing measures: school closure, increased case isolation, workplace non-attendance and community contact reduction. We compared the modelled results of final attack rates in the absence of any interventions and the effect of school closure as a single intervention with other published individual based models of pandemic influenza in the developed world. RESULTS We showed that published individual based models estimate similar final attack rates over a range of values for R(0) in a pandemic where no interventions have been implemented; that multiple social distancing measures applied early and continuously can be very effective in interrupting transmission of the pandemic virus for R(0) values up to 2.5; and that different conclusions reached on the simulated benefit of school closure in published models appear to result from differences in assumptions about the timing and duration of school closure and flow-on effects on other social contacts resulting from school closure. CONCLUSION Models of the spread and control of pandemic influenza have the potential to assist policy makers with decisions about which control strategies to adopt. However, attention needs to be given by policy makers to the assumptions underpinning both the models and the control strategies examined.
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Affiliation(s)
- George J Milne
- School of Computer Science and Software Engineering, The University of Western Australia, Crawley, Western Australia, Australia.
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768
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Basta NE, Halloran ME, Matrajt L, Longini IM. Estimating influenza vaccine efficacy from challenge and community-based study data. Am J Epidemiol 2008; 168:1343-52. [PMID: 18974084 PMCID: PMC2638553 DOI: 10.1093/aje/kwn259] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this paper, the authors provide estimates of 4 measures of vaccine efficacy for live, attenuated and inactivated influenza vaccine based on secondary analysis of 5 experimental influenza challenge studies in seronegative adults and community-based vaccine trials. The 4 vaccine efficacy measures are for susceptibility (VES), symptomatic illness given infection (VEP), infection and illness (VESP), and infectiousness (VEI). The authors also propose a combined (VEC) measure of the reduction in transmission in the entire population based on all of the above efficacy measures. Live influenza vaccine and inactivated vaccine provided similar protection against laboratory-confirmed infection (for live vaccine: VES = 41%, 95% confidence interval (CI): 15, 66; for inactivated vaccine: VES = 43%, 95% CI: 8, 79). Live vaccine had a higher efficacy for illness given infection (VEP = 67%, 95% CI: 24, 100) than inactivated vaccine (VEP = 29%, 95% CI: −19, 76), although the difference was not statistically significant. VESP for the live vaccine was higher than for the inactivated vaccine. VEI estimates were particularly low for these influenza vaccines. VESP and VEC can remain high for both vaccines, even when VEI is relatively low, as long as the other 2 measures of vaccine efficacy are relatively high.
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Affiliation(s)
- Nicole E Basta
- Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, Washington, USA
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769
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Identification of respiratory viruses in asymptomatic subjects: asymptomatic respiratory viral infections. Pediatr Infect Dis J 2008; 27:1103-7. [PMID: 18978518 DOI: 10.1097/inf.0b013e31817e695d] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The medical literature of the past 4 decades was searched regarding respiratory virus detection by polymerase chain reaction and conventional methods (culture, antigen detection, serology) in asymptomatic subjects in an attempt to determine the prevalence and clinical significance of such viruses in normal persons.
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770
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Handel A, Longini IM, Antia R. Antiviral resistance and the control of pandemic influenza: the roles of stochasticity, evolution and model details. J Theor Biol 2008; 256:117-25. [PMID: 18952105 DOI: 10.1016/j.jtbi.2008.09.021] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Revised: 09/09/2008] [Accepted: 09/18/2008] [Indexed: 11/30/2022]
Abstract
Antiviral drugs, most notably the neuraminidase inhibitors, are an important component of control strategies aimed to prevent or limit any future influenza pandemic. The potential large-scale use of antiviral drugs brings with it the danger of drug resistance evolution. A number of recent studies have shown that the emergence of drug-resistant influenza could undermine the usefulness of antiviral drugs for the control of an epidemic or pandemic outbreak. While these studies have provided important insights, the inherently stochastic nature of resistance generation and spread, as well as the potential for ongoing evolution of the resistant strain have not been fully addressed. Here, we study a stochastic model of drug resistance emergence and consecutive evolution of the resistant strain in response to antiviral control during an influenza pandemic. We find that taking into consideration the ongoing evolution of the resistant strain does not increase the probability of resistance emergence; however, it increases the total number of infecteds if a resistant outbreak occurs. Our study further shows that taking stochasticity into account leads to results that can differ from deterministic models. Specifically, we find that rapid and strong control cannot only contain a drug sensitive outbreak, it can also prevent a resistant outbreak from occurring. We find that the best control strategy is early intervention heavily based on prophylaxis at a level that leads to outbreak containment. If containment is not possible, mitigation works best at intermediate levels of antiviral control. Finally, we show that the results are not very sensitive to the way resistance generation is modeled.
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Affiliation(s)
- Andreas Handel
- Department of Biology, Emory University, Atlanta, GA 30322, USA.
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771
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Kernéis S, Grais RF, Boëlle PY, Flahault A, Vergu E. Does the effectiveness of control measures depend on the influenza pandemic profile? PLoS One 2008; 3:e1478. [PMID: 18213386 PMCID: PMC2198944 DOI: 10.1371/journal.pone.0001478] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Accepted: 12/24/2007] [Indexed: 11/19/2022] Open
Abstract
Background Although strategies to contain influenza pandemics are well studied, the characterization and the implications of different geographical and temporal diffusion patterns of the pandemic have been given less attention. Methodology/Main Findings Using a well-documented metapopulation model incorporating air travel between 52 major world cities, we identified potential influenza pandemic diffusion profiles and examined how the impact of interventions might be affected by this heterogeneity. Clustering methods applied to a set of pandemic simulations, characterized by seven parameters related to the conditions of emergence that were varied following Latin hypercube sampling, were used to identify six pandemic profiles exhibiting different characteristics notably in terms of global burden (from 415 to >160 million of cases) and duration (from 26 to 360 days). A multivariate sensitivity analysis showed that the transmission rate and proportion of susceptibles have a strong impact on the pandemic diffusion. The correlation between interventions and pandemic outcomes were analyzed for two specific profiles: a fast, massive pandemic and a slow building, long-lasting one. In both cases, the date of introduction for five control measures (masks, isolation, prophylactic or therapeutic use of antivirals, vaccination) correlated strongly with pandemic outcomes. Conversely, the coverage and efficacy of these interventions only moderately correlated with pandemic outcomes in the case of a massive pandemic. Pre-pandemic vaccination influenced pandemic outcomes in both profiles, while travel restriction was the only measure without any measurable effect in either. Conclusions Our study highlights: (i) the great heterogeneity in possible profiles of a future influenza pandemic; (ii) the value of being well prepared in every country since a pandemic may have heavy consequences wherever and whenever it starts; (iii) the need to quickly implement control measures and even to anticipate pandemic emergence through pre-pandemic vaccination; and (iv) the value of combining all available control measures except perhaps travel restrictions.
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Affiliation(s)
- Solen Kernéis
- Université Pierre et Marie Curie-Paris6, UMR-S 707, Paris, France
- INSERM, UMR-S 707, Paris, France
| | - Rebecca F. Grais
- Université Pierre et Marie Curie-Paris6, UMR-S 707, Paris, France
- INSERM, UMR-S 707, Paris, France
| | - Pierre-Yves Boëlle
- Université Pierre et Marie Curie-Paris6, UMR-S 707, Paris, France
- INSERM, UMR-S 707, Paris, France
| | - Antoine Flahault
- Université Pierre et Marie Curie-Paris6, UMR-S 707, Paris, France
- INSERM, UMR-S 707, Paris, France
| | - Elisabeta Vergu
- INRA, UR341 Mathématiques et Informatique Appliquées, Jouy-en-Josas, France
- * To whom correspondence should be addressed. E-mail:
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