Epidemiology, Clinical Features, Treatment, and Outcomes of Cases of Influenza A Infection During the 2009 Influenza Pandemic in Northern Taiwan

Introduction Findings from the community-based Canadian Sentinel Practitioner Surveillance Network (SPSN) suggest children were more affected by the 2018/19 influenza A(H1N1)pdm09 epidemic. Aim To compare the age distribution of A(H1N1)pdm09 cases in 2018/19 to prior seasonal influenza epidemics in Canada. Methods The age distribution of unvaccinated influenza A(H1N1)pdm09 cases and test-negative controls were compared across A(H1N1)pdm09-dominant epidemics in 2018/19, 2015/16 and 2013/14 and with the general population of SPSN provinces. Similar comparisons were undertaken for influenza A(H3N2)-dominant epidemics. Results In 2018/19, more influenza A(H1N1)pdm09 cases were under 10 years old than controls (29% vs 16%; p < 0.001). In particular, children aged 5–9 years comprised 14% of cases, greater than their contribution to controls (4%) or the general population (5%) and at least twice their contribution in 2015/16 (7%; p < 0.001) or 2013/14 (5%; p < 0.001). Conversely, children aged 10–19 years (11% of the population) were under-represented among A(H1N1)pdm09 cases versus controls in 2018/19 (7% vs 12%; p < 0.001), 2015/16 (7% vs 13%; p < 0.001) and 2013/14 (9% vs 12%; p = 0.12). Conclusion Children under 10 years old contributed more to outpatient A(H1N1)pdm09 medical visits in 2018/19 than prior seasonal epidemics in Canada. In 2018/19, all children under 10 years old were born after the 2009 A(H1N1)pdm09 pandemic and therefore lacked pandemic-induced immunity. In addition, more than half those born after 2009 now attend school (i.e. 5–9-year-olds), a socio-behavioural context that may enhance transmission and did not apply during prior A(H1N1)pdm09 epidemics.

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Clinical impact of influenza – lessons learnt from the pandemic influenza A (H1N1) 2009

Microbiology Australia ◽

10.1071/ma11029 ◽

2011 ◽

Vol 32 (1) ◽

pp. 29

Author(s):

Alex Dierig ◽

Gulam Khandaker ◽

Robert Booy

Keyword(s):

Clinical Features ◽

Pandemic Influenza ◽

Influenza A ◽

Influenza Pandemic ◽

Gastrointestinal Symptoms ◽

H1n1 Influenza ◽

World Health ◽

Pandemic H1n1 ◽

Pandemic H1n1 Influenza ◽

Influenza A H1n1

Influenza is generally an acute, self-limiting, febrile illness without further complications in the majority of people. However, it can be associated with severe morbidity and mortality and the burden of the disease on society is likely to be underestimated. In 2009 an outbreak of H1N1 influenza A virus infection was detected in Mexico with further cases soon observed worldwide. Subsequently, in June 2009, the first influenza pandemic of the 21st century due to influenza A (H1N1) was declared by the World Health Organization (WHO). There were many uncertainties regarding the virulence, clinical symptoms and epidemiological features of this newly evolved influenza A strain. Over time, many similarities, but also some differences between the pandemic H1N1 influenza A and seasonal influenza were identified. We recently performed a systematic review of the literature, looking at articles published between 1 April 2009 and 31 January 2010, to identify the epidemiological and clinical features of the pandemic H1N1 influenza. In this current article we compare our findings with others from the international literature. There was more severe impact on young and healthy adults, children, pregnant women and the obese. Clinical features in general were similar between seasonal and pandemic influenza; however, there were more gastrointestinal symptoms associated with pandemic H1N1 influenza. Shortness of breath was characteristic of more severe pH1N1 2009 infection with a higher possibility of being admitted to an intensive care unit (ICU).

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Pandemic influenza A(H1N1) 2009 breakthrough infections and estimates of vaccine effectiveness in Germany 2009-2010

Eurosurveillance ◽

10.2807/ese.15.18.19561-en ◽

2010 ◽

Vol 15 (18) ◽

Author(s):

O Wichmann ◽

P Stöcker ◽

G Poggensee ◽

D Altmann ◽

D Walter ◽

...

Keyword(s):

Pandemic Influenza ◽

Influenza A ◽

Influenza Pandemic ◽

Rapid Assessment ◽

Screening Method ◽

Age Groups ◽

Vaccine Effectiveness ◽

Influenza A H1n1 ◽

Reported Data ◽

2009 Influenza Pandemic

During the 2009 influenza pandemic, a monovalent AS03-adjuvanted vaccine was almost exclusively used in Germany for immunisation against the 2009 pandemic influenza A(H1N1) virus. One-dose vaccination was recommended for all age groups. We applied the screening method for the rapid assessment of vaccine effectiveness (VE) based on reported data of vaccinated and unvaccinated pandemic influenza cases and vaccination coverage estimates. Preliminary results demonstrate excellent VE in persons aged 14-59 years (96.8%; 95% confidence interval (CI): 95.2-97.9) and moderately high VE in those 60 years or older (83.3%; 95% CI: 71.0-90.5).

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Severe respiratory illness of unexplained etiology during the 2009 influenza pandemic: Analysis of Clinical Features and Outcomes

Human Vaccines & Immunotherapeutics ◽

10.1080/21645515.2017.1370162 ◽

2017 ◽

Vol 13 (11) ◽

pp. 2669-2673

Author(s):

Jennifer Potter ◽

Salaheddin M. Mahmud

Keyword(s):

Clinical Features ◽

Influenza Pandemic ◽

Respiratory Illness ◽

2009 Influenza Pandemic ◽

Severe Respiratory Illness

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Global dynamic spatiotemporal pattern of seasonal influenza since 2009 influenza pandemic

Infectious Diseases of Poverty ◽

10.1186/s40249-019-0618-5 ◽

2020 ◽

Vol 9 (1) ◽

Cited By ~ 2

Author(s):

Zhi-Wei Xu ◽

Zhong-Jie Li ◽

Wen-Biao Hu

Keyword(s):

South Africa ◽

Influenza A ◽

Seasonal Influenza ◽

Influenza Pandemic ◽

Influenza Viruses ◽

Sub Saharan Africa ◽

Spatiotemporal Pattern ◽

Influenza B ◽

2009 Influenza Pandemic ◽

Influenza Seasonality

Abstract Background Understanding the global spatiotemporal pattern of seasonal influenza is essential for influenza control and prevention. Available data on the updated global spatiotemporal pattern of seasonal influenza are scarce. This study aimed to assess the spatiotemporal pattern of seasonal influenza after the 2009 influenza pandemic. Methods Weekly influenza surveillance data in 86 countries from 2010 to 2017 were obtained from FluNet. First, the proportion of influenza A in total influenza viruses (PA) was calculated. Second, weekly numbers of influenza positive virus (A and B) were divided by the total number of samples processed to get weekly positive rates of influenza A (RWA) and influenza B (RWB). Third, the average positive rates of influenza A (RA) and influenza B (RB) for each country were calculated by averaging RWA, and RWB of 52 weeks. A Kruskal-Wallis test was conducted to examine if the year-to-year change in PA in all countries were significant, and a universal kriging method with linear semivariogram model was used to extrapolate RA and RB in all countries. Results PA ranged from 0.43 in Zambia to 0.98 in Belarus, and PA in countries with higher income was greater than those countries with lower income. The spatial patterns of high RB were the highest in sub-Saharan Africa, Asia-Pacific region and South America. RWA peaked in early weeks in temperate countries, and the peak of RWB occurred a bit later. There were some temperate countries with non-distinct influenza seasonality (e.g., Mauritius and Maldives) and some tropical/subtropical countries with distinct influenza seasonality (e.g., Chile and South Africa). Conclusions Influenza seasonality is not predictable in some temperate countries, and it is distinct in Chile, Argentina and South Africa, implying that the optimal timing for influenza vaccination needs to be chosen with caution in these unpredictable countries.

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Myocarditis Associated with Influenza A H1N1pdm2009

Influenza Research and Treatment ◽

10.1155/2012/351979 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8 ◽

Cited By ~ 17

Author(s):

Akira Ukimura ◽

Hidetoshi Satomi ◽

Yukimasa Ooi ◽

Yumiko Kanzaki

Keyword(s):

Influenza A ◽

Case Reports ◽

Acute Myocarditis ◽

Influenza Pandemic ◽

Influenza Infection ◽

Clinical Severity ◽

Fulminant Myocarditis ◽

Circulatory Support ◽

Influenza Pandemics ◽

2009 Influenza Pandemic

Acute myocarditis is a well-known complication of influenza infection. The frequency of myocardial involvement in influenza infection varies widely, with the clinical severity ranging from asymptomatic to fulminant varieties. The worst cases can result in death due to impaired cardiac function, although such fulminant myocarditis associated with influenza infection is rare, as shown by previous papers. Following the 2009 influenza pandemic, we reported on the clinical features of a cohort of 15 patients in Japan with H1N1pdm2009 myocarditis. In our subsequent survey of the literature for case reports or series of patients with myocarditis associated with H1N1pdm2009, we identified 58 detailed cases. We discuss here the high prevalence of fulminant myocarditis (36/58, 62%) among patients reported to have myocarditis associated with H1N1pdm2009. Mechanical circulatory support was required in 17 of the patients with fulminant myocarditis, 13 of whom recovered. We stress the need for increased awareness of influenza-associated myocarditis; such knowledge will facilitate earlier diagnosis and treatment of this fatal complication during future influenza pandemics.

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Drug susceptibility of influenza A/H3N2 strains co-circulating during 2009 influenza pandemic: First report from Mumbai

Infection Genetics and Evolution ◽

10.1016/j.meegid.2014.11.005 ◽

2015 ◽

Vol 29 ◽

pp. 75-81 ◽

Cited By ~ 1

Author(s):

Devanshi J. Gohil ◽

Sweta T. Kothari ◽

Pramod S. Shinde ◽

Anand S. Chintakrindi ◽

Rhuta Meharunkar ◽

...

Keyword(s):

Influenza A ◽

Influenza Pandemic ◽

Drug Susceptibility ◽

First Report ◽

2009 Influenza Pandemic

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Influenza – our constant companion

Microbiology Australia ◽

10.1071/ma11002 ◽

2011 ◽

Vol 32 (1) ◽

pp. 2

Author(s):

Ian G Barr ◽

Paul W Selleck

Keyword(s):

Influenza A ◽

Influenza Pandemic ◽

Good Reason ◽

World Health ◽

Director General ◽

Pandemic Preparedness ◽

The World ◽

Health Organization ◽

2009 Influenza Pandemic ◽

Novel Influenza A

On 11 June 2009, Dr Margaret Chan, the Director-General of the World Health Organization, announced to the world that following the emergence of a novel influenza A virus in late April 2009 and its extensive spread that, ?I have therefore decided to raise the level of influenza pandemic alert from phase 5 to phase 6. The world is now at the start of the 2009 influenza pandemic.? Dr Chan also commented, ?No previous pandemic has been detected so early or watched so closely, in real-time, right at the very beginning. The world can now reap the benefits of investments, over the last five years, in pandemic preparedness.? Also observed was that, ?Globally, we have good reason to believe that this pandemic, at least in its early days, will be of moderate severity?.

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Identification of Amino Acid Substitutions Supporting Antigenic Change of Influenza A(H1N1)pdm09 Viruses

Journal of Virology ◽

10.1128/jvi.02962-14 ◽

2015 ◽

Vol 89 (7) ◽

pp. 3763-3775 ◽

Cited By ~ 50

Author(s):

Björn F. Koel ◽

Ramona Mögling ◽

Salin Chutinimitkul ◽

Pieter L. Fraaij ◽

David F. Burke ◽

...

Keyword(s):

Amino Acid ◽

Receptor Binding ◽

Influenza A ◽

Influenza Pandemic ◽

Amino Acid Substitutions ◽

Receptor Binding Site ◽

Population Immunity ◽

Influenza A H1n1 ◽

Hemagglutinin Protein ◽

2009 Influenza Pandemic

ABSTRACTThe majority of currently circulating influenza A(H1N1) viruses are antigenically similar to the virus that caused the 2009 influenza pandemic. However, antigenic variants are expected to emerge as population immunity increases. Amino acid substitutions in the hemagglutinin protein can result in escape from neutralizing antibodies, affect viral fitness, and change receptor preference. In this study, we constructed mutants with substitutions in the hemagglutinin of A/Netherlands/602/09 in an attenuated backbone to explore amino acid changes that may contribute to emergence of antigenic variants in the human population. Our analysis revealed that single substitutions affecting the loop that consists of amino acid positions 151 to 159 located adjacent to the receptor binding site caused escape from ferret and human antibodies elicited after primary A(H1N1)pdm09 virus infection. The majority of these substitutions resulted in similar or increased replication efficiencyin vitrocompared to that of the virus carrying the wild-type hemagglutinin and did not result in a change of receptor preference. However, none of the substitutions was sufficient for escape from the antibodies in sera from individuals that experienced both seasonal and pandemic A(H1N1) virus infections. These results suggest that antibodies directed against epitopes on seasonal A(H1N1) viruses contribute to neutralization of A(H1N1)pdm09 antigenic variants, thereby limiting the number of possible substitutions that could lead to escape from population immunity.IMPORTANCEInfluenza A viruses can cause significant morbidity and mortality in humans. Amino acid substitutions in the hemagglutinin protein can result in escape from antibody-mediated neutralization. This allows the virus to reinfect individuals that have acquired immunity to previously circulating strains through infection or vaccination. To date, the vast majority of A(H1N1)pdm09 strains remain antigenically similar to the virus that caused the 2009 influenza pandemic. However, antigenic variants are expected to emerge as a result of increasing population immunity. We show that single amino acid substitutions near the receptor binding site were sufficient to escape from antibodies specific for A(H1N1)pdm09 viruses but not from antibodies elicited in response to infections with seasonal A(H1N1) and A(H1N1)pdm09 viruses. This study identified substitutions in A(H1N1)pdm09 viruses that support escape from population immunity but also suggested that the number of potential escape variants is limited by previous exposure to seasonal A(H1N1) viruses.

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