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Influenza Pandemic (influenza + pandemic)
Selected AbstractsSurge Capacity Associated with Restrictions on Nonurgent Hospital Utilization and Expected Admissions during an Influenza Pandemic: Lessons from the Toronto Severe Acute Respiratory Syndrome OutbreakACADEMIC EMERGENCY MEDICINE, Issue 11 2006Michael J. Schull MD Background Current influenza pandemic models predict a surge in influenza-related hospitalizations in affected jurisdictions. One proposed strategy to increase hospital surge capacity is to restrict elective hospitalizations, yet the degree to which this measure would meet the anticipated is unknown. Objectives To compare the reduction in hospitalizations resulting from widespread nonurgent hospital admission restrictions during the Toronto severe acute respiratory syndrome (SARS) outbreak with the expected increase in admissions resulting from an influenza pandemic in Toronto. Methods The authors compared the expected influenza-related hospitalizations in the first eight weeks of a mild, moderate, or severe pandemic with the actual reduction in the number of hospital admissions in Toronto, Ontario, during the first eight weeks of the SARS-related restrictions. Results Influenza modeling for Toronto predicts that there will be 4,819, 8,032, or 11,245 influenza-related admissions in the first eight weeks of a mild, moderate, or severe pandemic, respectively. In the first eight weeks of SARS-related hospital admission restrictions, there were 3,654 fewer hospitalizations than expected in Toronto, representing a modest 12% decrease in the overall admission rate (a reduction of 1.40 admissions per 1,000 population). Therefore, influenza-related admissions could exceed the reduction in admissions resulting from restricted hospital utilization by 1,165 to 7,591 patient admissions, depending on pandemic severity, which corresponds to an excess of 0.44 to 2.91 influenza-related admissions per 1,000 population per eight weeks, and an increase of 4% to 25% in the overall number of admissions, when compared with nonpandemic conditions. Conclusions Pandemic modeling for Toronto suggests that influenza-related admissions would exceed the reduction in hospitalizations seen during SARS-related nonurgent hospital admission restrictions, even in a mild pandemic. Sufficient surge capacity in a pandemic will likely require the implementation of other measures, including possibly stricter implementation of hospital utilization restrictions. [source] Impact of an Influenza Pandemic on the Mortality of Congestive Heart Failure in Older Japanese: The 1998 Japanese Influenza PandemicJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 5 2001Munetoshi Narukawa No abstract is available for this article. [source] Preparedness for Influenza Pandemic in Hong Kong Nursing UnitsJOURNAL OF NURSING SCHOLARSHIP, Issue 4 2006Agnes Tiwari Background: To present preparedness planning for an influenza pandemic for two nursing subunits: nursing services in hospitals and schools of nursing in universities. Discussion: The preparedness plan is modeled on a modified Haddon matrix, a logical approach to identify measures appropriate for the pre-event, event, and postevent phases of an influenza pandemic. For the pre-event phase, the objective is to ensure preparedness for the potential pandemic outbreak through training, communication, surveillance, infection control, and vaccination. Once the pandemic outbreak is declared, the aim is to implement effective measures to ensure a rapid and appropriate response. For the postevent phase, the plan is focused on the restoration of core functions, vigilance for a second or possibly more waves of the pandemic, and psychosocial support to staff and students. Conclusion: Measures required to prepare for, respond to, and manage the consequences of influenza pandemic are identified. This planning indicates the need to balance a logical approach with contextual perspectives and the importance for nursing leaders to develop plans for subunits of larger entities. [source] Global Public Health Implications of a Mass Gathering in Mecca, Saudi Arabia During the Midst of an Influenza PandemicJOURNAL OF TRAVEL MEDICINE, Issue 2 2010Kamran Khan MD Background. Every year millions of pilgrims from around the world gather under extremely crowded conditions in Mecca, Saudi Arabia to perform the Hajj. In 2009, the Hajj coincided with influenza season during the midst of an influenza A (H1N1) pandemic. After the Hajj, resource-limited countries with large numbers of traveling pilgrims could be vulnerable, given their limited ability to purchase H1N1 vaccine and capacity to respond to a possible wave of H1N1 introduced via returning pilgrims. Methods. We studied the worldwide migration of pilgrims traveling to Mecca to perform the Hajj in 2008 using data from the Saudi Ministry of Health and international air traffic departing Saudi Arabia after the 2008 Hajj using worldwide airline ticket sales data. We used gross national income (GNI) per capita as a surrogate marker of a country's ability to mobilize an effective response to H1N1. Results. In 2008, 2.5 million pilgrims from 140 countries performed the Hajj. Pilgrims (1.7 million) were of international (non-Saudi) origin, of which 91.0% traveled to Saudi Arabia via commercial flights. International pilgrims (11.3%) originated from low-income countries, with the greatest numbers traveling from Bangladesh (50,419), Afghanistan (32,621), and Yemen (28,018). Conclusions. Nearly 200,000 pilgrims that performed the Hajj in 2008 originated from the world's most resource-limited countries, where access to H1N1 vaccine and capacity to detect and respond to H1N1 in returning pilgrims are extremely limited. International efforts may be needed to assist resource-limited countries that are vulnerable to the impact of H1N1 during the 2009 to 2010 influenza season. [source] Bioprocess Engineering Issues That Would Be Faced in Producing a DNA Vaccine at up to 100 m3 Fermentation Scale for an Influenza PandemicBIOTECHNOLOGY PROGRESS, Issue 6 2005Mike Hoare The risk of a pandemic with a virulent form of influenza is acknowledged by the World Health Organization (WHO) and other agencies. Current vaccine production facilities would be unable to meet the global requirement for vaccine. As a possible supplement a DNA vaccine may be appropriate, and bioprocess engineering factors bearing on the use of existing biopharmaceutical and antibiotics plants to produce it are described. This approach addresses the uncertainty of timing of a pandemic that precludes purpose-built facilities. The strengths and weaknesses of alternative downstream processing routes are analyzed, and several gaps in public domain information are addressed. The conclusion is that such processing would be challenging but feasible. [source] Surge Capacity Associated with Restrictions on Nonurgent Hospital Utilization and Expected Admissions during an Influenza Pandemic: Lessons from the Toronto Severe Acute Respiratory Syndrome OutbreakACADEMIC EMERGENCY MEDICINE, Issue 11 2006Michael J. Schull MD Background Current influenza pandemic models predict a surge in influenza-related hospitalizations in affected jurisdictions. One proposed strategy to increase hospital surge capacity is to restrict elective hospitalizations, yet the degree to which this measure would meet the anticipated is unknown. Objectives To compare the reduction in hospitalizations resulting from widespread nonurgent hospital admission restrictions during the Toronto severe acute respiratory syndrome (SARS) outbreak with the expected increase in admissions resulting from an influenza pandemic in Toronto. Methods The authors compared the expected influenza-related hospitalizations in the first eight weeks of a mild, moderate, or severe pandemic with the actual reduction in the number of hospital admissions in Toronto, Ontario, during the first eight weeks of the SARS-related restrictions. Results Influenza modeling for Toronto predicts that there will be 4,819, 8,032, or 11,245 influenza-related admissions in the first eight weeks of a mild, moderate, or severe pandemic, respectively. In the first eight weeks of SARS-related hospital admission restrictions, there were 3,654 fewer hospitalizations than expected in Toronto, representing a modest 12% decrease in the overall admission rate (a reduction of 1.40 admissions per 1,000 population). Therefore, influenza-related admissions could exceed the reduction in admissions resulting from restricted hospital utilization by 1,165 to 7,591 patient admissions, depending on pandemic severity, which corresponds to an excess of 0.44 to 2.91 influenza-related admissions per 1,000 population per eight weeks, and an increase of 4% to 25% in the overall number of admissions, when compared with nonpandemic conditions. Conclusions Pandemic modeling for Toronto suggests that influenza-related admissions would exceed the reduction in hospitalizations seen during SARS-related nonurgent hospital admission restrictions, even in a mild pandemic. Sufficient surge capacity in a pandemic will likely require the implementation of other measures, including possibly stricter implementation of hospital utilization restrictions. [source] Investment in antiviral drugs: a real options approachHEALTH ECONOMICS, Issue 10 2010Arthur E. Attema Abstract Real options analysis is a promising approach to model investment under uncertainty. We employ this approach to value stockpiling of antiviral drugs as a precautionary measure against a possible influenza pandemic. Modifications of the real options approach to include risk attitude and deviations from expected utility are presented. We show that risk aversion counteracts the tendency to delay investment for this case of precautionary investment, which is in contrast to earlier applications of risk aversion to real options analysis. Moreover, we provide a numerical example using real world data and discuss the implications of real options analysis for health policy. Suggestions for further extensions of the model and a comparison with the expected value of information analysis are put forward. Copyright © 2009 John Wiley & Sons, Ltd. [source] Dynamic versus static models in cost-effectiveness analyses of anti-viral drug therapy to mitigate an influenza pandemicHEALTH ECONOMICS, Issue 5 2010Anna K. Lugnér Abstract Conventional (static) models used in health economics implicitly assume that the probability of disease exposure is constant over time and unaffected by interventions. For transmissible infectious diseases this is not realistic and another class of models is required, so-called dynamic models. This study aims to examine the differences between one dynamic and one static model, estimating the effects of therapeutic treatment with antiviral (AV) drugs during an influenza pandemic in the Netherlands. Specifically, we focus on the sensitivity of the cost-effectiveness ratios to model choice, to the assumed drug coverage, and to the value of several epidemiological factors. Therapeutic use of AV-drugs is cost-effective compared with non-intervention, irrespective of which model approach is chosen. The findings further show that: (1) the cost-effectiveness ratio according to the static model is insensitive to the size of a pandemic, whereas the ratio according to the dynamic model increases with the size of a pandemic; (2) according to the dynamic model, the cost per infection and the life-years gained per treatment are not constant but depend on the proportion of cases that are treated; and (3) the age-specific clinical attack rates affect the sensitivity of cost-effectiveness ratio to model choice. Copyright © 2009 John Wiley & Sons, Ltd. [source] The 2009 influenza pandemic beginsINFLUENZA AND OTHER RESPIRATORY VIRUSES, Issue 5 2009John M. Wood No abstract is available for this article. [source] National pandemic influenza preparedness planningINFLUENZA AND OTHER RESPIRATORY VIRUSES, Issue 4 2009Eduardo Azziz-Baumgartner Abstract, The recent outbreaks of influenza A/H5N1 and ,swine influenza' A/H1N1 have caused global concern over the potential for a new influenza pandemic. Although it is impossible to predict when the next pandemic will occur, appropriate planning is still needed to maximize efficient use of resources and to minimize loss of life and productivity. Many tools now exist to assist countries in evaluating their plans but there is little to aid in writing of the plans. This study discusses the process of drafting a pandemic influenza preparedness plan for developing countries that conforms to the International Health Regulations of 2005 and recommendations of the World Health Organization. Stakeholders from many sectors should be involved in drafting a comprehensive pandemic influenza plan that addresses all levels of preparedness. [source] The burden of influenza in East and South-East Asia: a review of the English language literatureINFLUENZA AND OTHER RESPIRATORY VIRUSES, Issue 3 2008James M. Simmerman Abstract, While human infections with avian influenza A (H5NI) viruses in Asia have prompted concerns about an influenza pandemic, the burden of human influenza in East and Southeast Asia has received far less attention. We conducted a review of English language articles on influenza in 18 countries in East and Southeast Asia published from 1980 to 2006 that were indexed on PubMed. Articles that described human influenza-associated illnesses among outpatients or hospitalized patients, influenza-associated deaths, or influenza-associated socioeconomic costs were reviewed. We found 35 articles from 9 countries that met criteria for inclusion in the review. The quality of articles varied substantially. Significant heterogeneity was noted in case definitions, sampling schemes and laboratory methods. Early studies relied on cell culture, had difficulties with specimen collection and handling, and reported a low burden of disease. The recent addition of PCR testing has greatly improved the proportion of respiratory illnesses diagnosed with influenza. These more recent studies reported that 11,26% of outpatient febrile illness and 6-14% of hospitalized pneumonia cases had laboratory-confirmed influenza infection. The influenza disease burden literature from East and Southeast Asia is limited but expanding. Recent studies using improved laboratory testing methods and indirect statistical approaches report a substantial burden of disease, similar to that of Europe and North America. Current increased international focus on influenza, coupled with unprecedented funding for surveillance and research, provide a unique opportunity to more comprehensively describe the burden of human influenza in the region. [source] Risk modelling in blood safety , review of methods, strengths and limitationsISBT SCIENCE SERIES: THE INTERNATIONAL JOURNAL OF INTRACELLULAR TRANSPORT, Issue n1 2010B. Custer Risk modelling studies in blood safety play an important but occasionally misunderstood role. These studies are intended to quantify and contrast risks and benefits. This information is critical for policy development and intervention decision-making. The limitations of risk modelling should be considered alongside the results obtained. The goal of this manuscript and presentation is to review current risk modelling techniques used in blood safety and to discuss the pros and cons of using this information in the decision-making process. The types of questions that can be answered include the extent of a risk or threat; implications of action or inaction; identification of effective strategies for risk management; or whether to adopt specific interventions. These analyses can be focused on a risk alone but are often combined with economic information to gain an understanding of feasible risk interventions given budgetary or other monetary considerations. Thus, analyses that include risk modelling provide insights along multiple lines. As important, the analyses also provide information on what is not known or uncertain about a potential hazard and how much that uncertainty may influence the decision-making process. Specific examples of the range of risk analyses in which the author has participated will be reviewed and will include ongoing process improvement in testing laboratories such as error identification/eradication, estimation of the risk of malaria exposure based on the specific locations of travel, evaluation of blood supply and demand during an influenza pandemic, cost-utility analyses of screening interventions for infectious diseases in countries with different human development indices, and insurance against emerging pathogen risk. Each of these analyses has a different purpose and seeks to answer different questions, but all rely on similar methods. The tool kit for risk analysis is broad and varied but does have limitations. The chief limitation of risk modelling is that risk analyses are not scientific experiments or otherwise controlled studies. Consequently, the analyses are more apt to be influenced by assumptions. These assumptions may be necessary to structure a problem in a way that will allow the question of interest to be answered or may result from incomplete or missing information. Another potential limitation is that commissioners of such studies, those who undertake them, and the intended audience, such as regulatory agencies, may have distinct and differing interpretations of the results. Risk modelling is a set of techniques that can be used to inform and support decision-making at all levels in transfusion medicine. Advances in risk modelling techniques allow for continued expansion in the scope of possible questions that can be analysed. Expanded use also improves the acceptance of the utility of these studies in blood safety and transfusion medicine. [source] Pandemic influenza and the hospitalist: Apocalypse when?JOURNAL OF HOSPITAL MEDICINE, Issue 2 2006James C. Pile MD Abstract Beginning with a cluster of human cases in Hong Kong in 1997, avian influenza (H5N1) has spread progressively through, and beyond, Asia in poultry and other birds; and has resulted in sporadic cases of human disease associated with high mortality. The potential for H5N1 influenza to cause a pandemic of human disease continues to be the subject of intense scrutiny by both the media and the scientific community. While the likelihood of such a prospect is uncertain, the inevitability of future pandemics of influenza is clear. Planning for the eventuality of a virulent influenza pandemic at the local, national and global level is critical to limiting the mortality and morbidity of such an occurrence. Hospitalists have a key role to play in institutional efforts to prepare for a influenza pandemic, and should be aware of lessons that my be applied from both the response to Hurricane Katrina, as well as the severe acute respiratory syndrome (SARS) epidemic. Journal of Hospital Medicine 2006;1:118,123. © 2006 Society of Hospital Medicine [source] Preparedness for Influenza Pandemic in Hong Kong Nursing UnitsJOURNAL OF NURSING SCHOLARSHIP, Issue 4 2006Agnes Tiwari Background: To present preparedness planning for an influenza pandemic for two nursing subunits: nursing services in hospitals and schools of nursing in universities. Discussion: The preparedness plan is modeled on a modified Haddon matrix, a logical approach to identify measures appropriate for the pre-event, event, and postevent phases of an influenza pandemic. For the pre-event phase, the objective is to ensure preparedness for the potential pandemic outbreak through training, communication, surveillance, infection control, and vaccination. Once the pandemic outbreak is declared, the aim is to implement effective measures to ensure a rapid and appropriate response. For the postevent phase, the plan is focused on the restoration of core functions, vigilance for a second or possibly more waves of the pandemic, and psychosocial support to staff and students. Conclusion: Measures required to prepare for, respond to, and manage the consequences of influenza pandemic are identified. This planning indicates the need to balance a logical approach with contextual perspectives and the importance for nursing leaders to develop plans for subunits of larger entities. [source] Avian influenza: risk, preparedness and the roles of public health nurses in Hong KongNURSING INQUIRY, Issue 1 2006Georgina Ho This paper provides an overview of the Hong Kong government's influenza preparedness plan and the key roles of public health nurses in that plan. The part played by Hong Kong public health nurses in the management of the avian influenza outbreak in Hong Kong in 1997 and the sudden acute respiratory syndrome outbreak in 2003, together with the capacity-building work they are now undertaking in preparing for an influenza pandemic, highlight their crucial role in public health. Recent strengthening of public health infrastructure in Hong Kong and heightened public awareness of public health issues have facilitated more proactive and effective public health nursing activities. [source] The design and use of an agent-based model to simulate the 1918 influenza epidemic at Norway House, ManitobaAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 3 2009Connie Carpenter Agent-based modeling provides a new approach to the study of virgin soil epidemics like the 1918 flu. In this bottom-up simulation approach, a landscape can be created and populated with a heterogeneous group of agents who move and interact in ways that more closely resemble human behavior than is usually seen in other modeling techniques. In this project, an agent-based model was constructed to simulate the spread of the 1918 influenza pandemic through the Norway House community in Manitoba, Canada. Archival, ethnographic, epidemiological, and biological information were used to aid in designing the structure of the model and to estimate values for model parameters. During the epidemic, Norway House was a Hudson's Bay Company post and a Swampy Cree-Métis settlement with an economy based on hunting, fishing, and the fur trade. The community followed a traditional, seasonal travel pattern of summer aggregation and winter dispersal. The model was used to examine how seasonal community structures and associated population movement patterns may have influenced disease transmission and epidemic spread. Simulations of the model clearly demonstrate that human behavior can significantly influence epidemic outcomes. Am. J. Hum. Biol. 2009. © 2008 Wiley-Liss, Inc. [source] Social contexts, syndemics, and infectious disease in northern Aboriginal populations,AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 2 2007D. Ann Herring Until the last half of the 20th century, infectious diseases dominated the health profile of northern North American Aboriginal communities. Research on the 1918 influenza pandemic exemplifies some of the ways in which the social context of European contact and ensuing economic developments affected the nature of infectious disease ecology as well as the frequency and severity of the problem. To understand these impacts it is necessary to consider the web of interactions among multiple pathogens, the biology of the human host, and the social environment in which people lived. At the very least, an understanding of the history of the impact of infectious diseases on northern North American communities requires attention not only to potential interactions among cocirculating pathogens, but their links to key social, historical, and economic factors that exacerbated their adverse effects and contributed to excess mortality. Am. J. Hum. Biol. 19:190,202, 2007. © 2007 Wiley-Liss, Inc. [source] Brief communication: Rethinking the impact of the 1918 influenza pandemic on sex differentials in mortalityAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2009L.A. Sawchuk Abstract This study will assess the general impact of the 1918 influenza on overall mortality and its impact on mortality attributable to pulmonary tuberculosis in a small-scale population. Using life table and decomposition methodologies, changes in mortality in Gibraltar used a scheme that identified a pre-epidemic period (1904,1917), the epidemic year (1918), and the post-epidemic period (1919,1927). Overall health in both sexes fell significantly in 1918 with a drop in life expectancy at birth, however, health quickly rebounded in the post-epidemic period. In the case of women, there was a significant increase in life expectancy at birth after the epidemic. The impact of influenza on the magnitude of sex differentials in the life expectancy at birth fell during epidemic year but returned to a level comparable to that of the pre-epidemic period. With respect to respiratory tuberculosis deaths, the immediate impact of influenza was restricted to only a significant increase in the rate among women (aged 15,54). In the post-epidemic period, tuberculosis mortality rates returned to the pre-epidemic state in both sexes. The findings from Gibraltar stand in contrast opposition to results reported for experience in the United States during the 1918 flu. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] An assessment of the validity of SOFA score based triage in H1N1 critically ill patients during an influenza pandemicANAESTHESIA, Issue 12 2009Z. Khan Summary Sequential Organ Failure Assessment (SOFA) score based triage of influenza A H1N1 critically ill patients has been proposed for surge capacity management as a guide for clinical decision making. We conducted a retrospective records review and SOFA scoring of critically ill patients with influenza A H1N1 in a mixed medical-surgical intensive care unit in an urban hospital. Eight critically ill patients with influenza A H1N1 were admitted to the intensive care unit. Their mean (range) age was 39 (26,52) years with a length of stay of 11 (3,17) days. All patients met SOFA score based triage admission criteria with a modal SOFA score of five. Five patients required invasive ventilation for a mean (range) of 5 (4,11) days. Five patients would have been considered for withdrawal of treatment using SOFA scoring guidelines at 48 h. All patients survived. We conclude that SOFA score based triage could lead to withdrawal of life support in critically ill patients who could survive with an acceptably low length of stay in the intensive care unit. [source] An observational cohort study of triage for critical care provision during pandemic influenza: ,clipboard physicians' or ,evidenced based medicine'?ANAESTHESIA, Issue 11 2009T. Guest Summary We assessed the impact of a United Kingdom government-recommended triage process, designed to guide the decision to admit patients to intensive care during an influenza pandemic, on patients in a teaching hospital intensive care unit. We found that applying the triage criteria to a current case-mix would result in 116 of the 255 patients (46%) admitted during the study period being denied intensive care treatment they would have otherwise received, of which 45 (39%) survived to hospital discharge. In turn, 69% of those categorised as too ill to warrant admission according to the criteria survived. The sensitivity and specificity of the triage category at ICU admission predicting mortality was 0.29 and 0.84, respectively. If the need for intensive care beds is estimated to be 275 patients per week, the triage criteria would not exclude enough patients to prevent the need for further rationing. We conclude that the proposed triage tool failed adequately to prioritise patients who would benefit from intensive care. [source] The impact of a human influenza pandemicANAESTHESIA, Issue 3 2006S. A. Booth No abstract is available for this article. [source] Register data suggest lower intelligence in men born the year after flu pandemic,ANNALS OF NEUROLOGY, Issue 3 2009Willy Eriksen MD Objective To test the hypothesis that prenatal exposure to the Hong Kong flu, an influenza pandemic that haunted Europe during winter 1969 to 1970, was associated with reduced intelligence in adulthood. Methods Data from the Medical Birth Register of Norway were linked with register data from the National Conscript Service. The sample comprised all registered boys born alive in single birth after 37 to 43 weeks' gestation during 1967 to 1973 (n = 205,634). Intelligence test scores, recorded at military conscription, were available for 182,913 individuals. Results The mean intelligence score increased from one birth year to another, except for a downturn in 1970. The birth year 1970 was inversely associated with intelligence score (,0.03 standard deviation [SD]; p < 0.001) after adjustments for birth characteristics, parental characteristics, and the trend of increasing scores over the 7 birth years. Analyses with the sample stratified by birth month showed that the inverse association between the birth year 1970 and intelligence score was significant only among men born in July (,0.04 SD; p = 0.049), August (,0.05 SD; p = 0.013), September (,0.09 SD; p < 0.001), and October (,0.06 SD; p = 0.008). Thus, the intelligence scores of the men born 6 to 9 months after the epidemic were lower than the mean values for the men born in the same months a few years before or after. Interpretation Early prenatal exposure to the Hong Kong flu may have interfered with fetal cerebral development and caused reduced intelligence in adulthood. Ann Neurol 2009;66:284,289 [source] Lessons from the H1N1 influenza pandemic in French overseas territories and interim reports from metropolitan FranceCLINICAL MICROBIOLOGY AND INFECTION, Issue 4 2010X. De Lamballerie No abstract is available for this article. [source] Genetic immunity and influenza pandemicsFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 1 2006Sergey N. Rumyantsev Abstract In addition to the great number of publications focused on the leading role of virus mutations and reassortment in the origin of pandemic influenza, general opinion emphasizes the victim side of the epidemic process. Based on the analysis and integration of relevant ecological, epidemiological, clinical, genetic and experimental data, the present article is focused on the evolution of ,virus , victim' ecological systems resulting in the formation of innate (i.e. genetic, constitutional) immunity in the involved species and populations. This kind of immunity functions today as the greatest natural barrier to the pandemic spread of influenza among humans and ecologically related kinds of animals. Global influenza pandemics can arise when the worldwide population contains at least a minimum number of people susceptible to a known or mutant influenza virus. Special attention is paid in this article to individual tests for the presence of this barrier, including the implications of specific findings for public health policy. Such tests could be based on in vitro observation of the action of relevant virus strains on primary cell cultures or on their cellular or molecular components extracted from individuals. The resources of the Human Genome Project should also be utilized. [source] Non-random reassortment in human influenza A virusesINFLUENZA AND OTHER RESPIRATORY VIRUSES, Issue 1 2008Raul Rabadan Background, The influenza A virus has two basic modes of evolution. Because of a high error rate in the process of replication by RNA polymerase, the viral genome drifts via accumulated mutations. The second mode of evolution is termed a shift, which results from the reassortment of the eight segments of this virus. When two different influenza viruses co-infect the same host cell, new virions can be released that contain segments from both parental strains. This type of shift has been the source of at least two of the influenza pandemics in the 20th century (H2N2 in 1957 and H3N2 in 1968). Objectives, The methods to measure these genetic shifts have not yet provided a quantitative answer to questions such as: what is the rate of genetic reassortment during a local epidemic? Are all possible reassortments equally likely or are there preferred patterns? Methods, To answer these questions and provide a quantitative way to measure genetic shifts, a new method for detecting reassortments from nucleotide sequence data was created that does not rely upon phylogenetic analysis. Two different sequence databases were used: human H3N2 viruses isolated in New York State between 1995 and 2006, and human H3N2 viruses isolated in New Zealand between 2000 and 2005. Results, Using this new method, we were able to reproduce all the reassortments found in earlier works, as well as detect, with very high confidence, many reassortments that were not detected by previous authors. We obtain a lower bound on the reassortment rate of 2,3 events per year, and find a clear preference for reassortments involving only one segment, most often hemagglutinin or neuraminidase. At a lower frequency several segments appear to reassort in vivo in defined groups as has been suggested previously in vitro. Conclusions, Our results strongly suggest that the patterns of reassortment in the viral population are not random. Deciphering these patterns can be a useful tool in attempting to understand and predict possible influenza pandemics. [source] | |||||||||||||