Age, influenza pandemics and disease dynamics

SUMMARYThe world is currently confronting the first influenza pandemic of the 21st century [caused by a novel pandemic influenza A (H1N1) virus]. Earlier pandemics have been characterized by age distributions that are distinct from those observed with seasonal influenza epidemics, with higher attack rates (and correspondingly increased proportionate or relative mortality) in younger individuals. While the genesis of protection against infection in older individuals during a pandemic is uncertain, differential vulnerability to infection by age has important implications for disease dynamics and control, and for choice of optimal vaccination strategies. Age-related vulnerability to infection may explain differences between school- and community-derived estimates of the reproductive number (R) for a newly emerged pandemic strain, and may also help explain the failure of a newly emerged influenza A (H1N1) virus strain to cause a pandemic in 1977. Age-related factors may also help explain variability in attack rates, and the size and impact of influenza epidemics across jurisdictions and between populations. In Canada, such effects have been observed in the apparently increased severity of outbreaks on Indigenous peoples' reserves. The implications of these patterns for vaccine allocation necessitate targeted research to understand age-related vulnerabilities early in an influenza pandemic.

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Sex- and Age-Related Differences in Morbidity Rates of 2009 Pandemic Influenza A H1N1 Virus of Swine Origin in Japan

PLoS ONE ◽

10.1371/journal.pone.0019409 ◽

2011 ◽

Vol 6 (4) ◽

pp. e19409 ◽

Cited By ~ 30

Author(s):

Nobuoki Eshima ◽

Osamu Tokumaru ◽

Shohei Hara ◽

Kira Bacal ◽

Seigo Korematsu ◽

...

Keyword(s):

Pandemic Influenza ◽

Influenza A ◽

H1n1 Virus ◽

Age Related ◽

Influenza A H1n1

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Immunophenotype Expressions and Cytokine Profiles of Influenza A H1N1 Virus Infection in Pediatric Patients in 2009

Disease Markers ◽

10.1155/2014/195453 ◽

2014 ◽

Vol 2014 ◽

pp. 1-6 ◽

Cited By ~ 3

Author(s):

Shih-Min Wang ◽

Yu-Ting Liao ◽

Yu-Shiang Hu ◽

Tzong-Shiann Ho ◽

Ching-Fen Shen ◽

...

Keyword(s):

Influenza A ◽

Pediatric Patients ◽

Mononuclear Cells ◽

H1n1 Virus ◽

Influenza Pandemic ◽

Influenza Infection ◽

Plasma Concentrations ◽

Pulmonary Complications ◽

Cytokine Profiles ◽

Influenza A H1n1

Background. A novel swine-origin influenza A H1N1 virus (S-OIV) caused human infection and acute respiratory illness in 2009, resulting in an influenza pandemic.Objectives. This study characterized the immune responses of S-OIV infection in pediatric patients at risk of pulmonary complications.Methods. All enrolled pediatric patients were confirmed virologically for S-OIV infection in 2009-2010, prospectively. Changes in cellular immunophenotypes were analyzed using flow cytometry. Plasma cytokine levels associated with S-OIV infection by pulmonary and without pulmonary complications were measured using cytokine cytometric bead assay kits.Results. A total of 85 patients with a mean age of 10.3 years were recruited. The level of C-reactive protein (CRP) was high in patients exhibiting pulmonary complications. The percentage of cellular immunophenotypes did not change between patients with and without pulmonary complications. The absolute numbers of peripheral blood mononuclear cells (PBMC), CD3, CD8, and CD16CD56 decreased with acute S-OIV pulmonary complications. Acute influenza infection with pulmonary complications was associated with high plasma concentrations of IL-1β, IL-6, IL-12, and IFN-γ.Conclusion. Immunophenotype studies have reported variability in immune response to the severity of S-OIV infections. Acute phase cytokine profiles of the 2009 S-OIV infection might have contributed to the pathogenesis of the pulmonary complications.

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Residual immunity in older people against the influenza A(H1N1) – recent experience in northern Spain

Eurosurveillance ◽

10.2807/ese.14.39.19344-en ◽

2009 ◽

Vol 14 (39) ◽

Cited By ~ 16

Author(s):

E Pérez-Trallero ◽

L Piñeiro ◽

D Vicente ◽

M Montes ◽

G Cilla

Keyword(s):

Pandemic Influenza ◽

Influenza A ◽

Seasonal Influenza ◽

H1n1 Virus ◽

Influenza Pandemic ◽

Age Groups ◽

H3n2 Virus ◽

Recent Experience ◽

Northern Spain ◽

Influenza A H1n1

The 2009 pandemic influenza A(H1N1) virus has a higher incidence in children and young adults, a pattern that has also been reported in seasonal influenza caused by the influenza A(H1N1) virus. We analysed age at infection in symptomatic patients with influenza in the Basque Country (northern Spain), reported through the sentinel influenza surveillance system which monitors 2.2-2.5% of the population. Between September 1999 and August 2009, influenza A(H3N2) or seasonal influenza A(H1N1) was detected in 941 patients, and from April to August 2009, pandemic influenza A(H1N1) was detected in 112 patients. The H3/H1 seasonal influenza ratio was between 3.3 and 3.4 in the under 60 year-olds, but 9.8 in older individuals, suggesting that people born before 1950 have residual immunity against the influenza A H1N1 subtype (both seasonal and pandemic). Introduction In 1957, the Asian influenza pandemic was caused by influenza A(H2N2) virus, which circulated until 1968 when it was displaced by the influenza A(H3N2) virus which was responsible for the Hong Kong pandemic. Before 1957, direct descendants of the influenza A(H1N1) virus that had caused the 1918 pandemic (Spanish flu) had circulated. In 1977, an influenza A(H1N1) strain re-emerged, which, together with the dominant influenza A(H3N2) strain, has been the cause of seasonal human influenza for more than three decades [1]. Despite the prolonged co-circulation of both subtypes, few studies have analysed their ability to affect distinct age groups. The current pandemic influenza A(H1N1) virus, influenza A(H1N1)v, which emerged in the spring of 2009, has spread throughout the world. The aim of this study was to compare the distribution in distinct age groups of infections caused by the two subtypes of seasonal influenza in the past 10 seasons and refer therelate this to recent infections due to influenza A(H1N1)v.

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Age-related sensitivity and pathological differences in infections by 2009 pandemic influenza A (H1N1) virus

Virology Journal ◽

10.1186/1743-422x-8-52 ◽

2011 ◽

Vol 8 (1) ◽

pp. 52 ◽

Cited By ~ 24

Author(s):

Shihui Sun ◽

Guangyu Zhao ◽

Wenjun Xiao ◽

Jingya Hu ◽

Yan Guo ◽

...

Keyword(s):

Pandemic Influenza ◽

Influenza A ◽

H1n1 Virus ◽

Age Related ◽

Influenza A H1n1

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2009 pandemic influenza A(H1N1) virus in Scotland: geographically variable immunity in Spring 2010, following the winter outbreak

Eurosurveillance ◽

10.2807/ese.15.24.19590-en ◽

2010 ◽

Vol 15 (24) ◽

Author(s):

W E Adamson ◽

S Maddi ◽

C Robertson ◽

S McDonagh ◽

P J Molyneaux ◽

...

Keyword(s):

Older People ◽

Pandemic Influenza ◽

Influenza A ◽

H1n1 Virus ◽

Age Groups ◽

Older Individuals ◽

Serum Samples ◽

Younger Adults ◽

Influenza A H1n1

We determined the age- and location-specific seroprevalence of antibodies against 2009 pandemic influenza A(H1N1) virus in Scotland following the first two waves of infection. Serum samples collected following the winter outbreak were analysed by microneutralisation assay. The proportion of positive sera varied significantly between cities and, in the case of Inverness, between age groups (with younger adults more likely to be positive than older individuals). This study demonstrates that older people are no longer more likely to have antibodies against the virus than younger adults.

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Model-based reconstruction of an epidemic using multiple datasets: understanding influenza A/H1N1 pandemic dynamics in Israel

Journal of The Royal Society Interface ◽

10.1098/rsif.2016.0099 ◽

2016 ◽

Vol 13 (116) ◽

pp. 20160099 ◽

Cited By ~ 3

Author(s):

R. Yaari ◽

G. Katriel ◽

L. Stone ◽

E. Mendelson ◽

M. Mandelboim ◽

...

Keyword(s):

School Children ◽

Disease Transmission ◽

Influenza A ◽

Influenza Pandemic ◽

Age Groups ◽

Absolute Humidity ◽

Transmission Model ◽

Reproductive Number ◽

Infection Pattern ◽

Influenza A H1n1

Intensified surveillance during the 2009 A/H1N1 influenza pandemic in Israel resulted in large virological and serological datasets, presenting a unique opportunity for investigating the pandemic dynamics. We employ a conditional likelihood approach for fitting a disease transmission model to virological and serological data, conditional on clinical data. The model is used to reconstruct the temporal pattern of the pandemic in Israel in five age-groups and evaluate the factors that shaped it. We estimate the reproductive number at the beginning of the pandemic to be R = 1.4. We find that the combined effect of varying absolute humidity conditions and school vacations (SVs) is responsible for the infection pattern, characterized by three epidemic waves. Overall attack rate is estimated at 32% (28–35%) with a large variation among the age-groups: the highest attack rates within school children and the lowest within the elderly. This pattern of infection is explained by a combination of the age-group contact structure and increasing immunity with age. We assess that SVs increased the overall attack rates by prolonging the pandemic into the winter. Vaccinating school children would have been the optimal strategy for minimizing infection rates in all age-groups.

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Mathematical Analysis of Epidemiological Model of Influenza a (H1N1) Virus Transmission Dynamics in Perspective of Bangladesh

GANIT Journal of Bangladesh Mathematical Society ◽

10.3329/ganit.v37i0.35724 ◽

2018 ◽

Vol 37 ◽

pp. 39-50 ◽

Cited By ~ 1

Author(s):

Rafiqul Islam ◽

Md Haider Ali Biswas ◽

ARM Jalal Uddin Jamali

Keyword(s):

Influenza A ◽

H1n1 Virus ◽

Herd Immunity ◽

Virus Transmission ◽

Transmission Dynamics ◽

Basic Reproductive Number ◽

Reproductive Number ◽

Numerical Result ◽

Influenza A H1n1 ◽

Novel Influenza A

This study deals with transmission dynamics of novel influenza A (H1N1) virus to understand the evolution of its epidemic in Bangladesh. For this purpose an SEIR model has been employed to study the dynamics of A (H1N1) virus relating to data of Bangladesh. To find threshold conditions, the equilibria and stability of the equilibria of the model have been determined and also analyzed. Basic Reproductive Number (R0) is determined relating to data of Bangladesh by which Herd Immunity Threshold has been estimated. Our numerical result suggests that vaccinating 12.69% population of Bangladesh can control spread of the pandemic novel A (H1N1) virus when outbreak occurs.GANIT J. Bangladesh Math. Soc.Vol. 37 (2017) 39-50

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The emergence of the novel H1N1 virus: implications for global mental health

International Psychogeriatrics ◽

10.1017/s1041610209990925 ◽

2009 ◽

Vol 21 (6) ◽

pp. 987-989 ◽

Cited By ~ 1

Author(s):

Sandra S. Chan ◽

Linda C. W. Lam ◽

Helen F. K. Chiu

Keyword(s):

Mental Health ◽

Influenza A ◽

H1n1 Virus ◽

Global Mental Health ◽

Influenza Pandemic ◽

World Health ◽

The Novel ◽

Influenza A H1n1 ◽

The World ◽

Health Organization

The emergence of the novel swine-origin influenza A (H1N1) virus in humans has aroused great concern among medical professionals about the possible evolution of a full-blown influenza pandemic, one on the scale of the “Spanish” influenza pandemic of 1918–19 (Belshe, 2009). It has been speculated that the return of a pandemic virus equivalent in pathogenicity to the virus of 1918 would likely kill more than 100 million people worldwide, including a large number of economically active young people (Taubenberger and Morens, 2006). Health administrations worldwide have stepped up reporting and surveillance of the deaths and illnesses associated with H1N1, and most countries have national strategies to fight the outbreak, though skeptics doubt how such plans could be operationalized, especially in developing countries (Coker, 2009). As of 6 July 2009, the cumulative total of H1N1 cases exceeds 90,000 in over 100 countries, with over 400 deaths directly related to the infection (World Health Organization, 2009a). Optimists might believe this pandemic is not going to match the scale of the historical 1918 pandemic given the relatively low fatality rate observed thus far. However, the World Health Organization has cautioned that we have just entered Phase 6 of the pandemic – i.e. we are in the early days of the 2009 flu pandemic (Chan, 2009). The course of the pandemic is thus unpredictable at this stage but it is evident that international multilateral plans and agreements have enabled much greater coordination of communication and action than ever before. The guidance behind these multilateral international actions, rooted in the World Health Organization's International Health Regulations (IHR) 2005, only came into being five years ago in response to the threat of emerging infectious diseases and particularly by the events related to the emergence of Severe Acute Respiratory Syndrome (SARS) (Katz, 2009). The morbidity and mortality directly resulting from this novel influenza A H1N1 outbreak are in the center of the world media's spotlight, but the potential impact of the pandemic on global mental health has not yet received the attention it deserves.

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