An ever changing virus 2 antigenic shift refers to an abrupt, major change in that results in a new influenza a subtype e. Less often, a person might get flu by touching a surface or object that has the flu virus on it and. Chapter 3 epidemiology and potential impact health protection. Enhanced surveillance of hpai and lpai ah7n9 viruses in poultry and humans, timely virus characterization, and ongoing assessments of the epidemiology of human infections with ah7n9 viruses are critical to guide prevention and control efforts and to provide information on the risk of these novel influenza a viruses to public health. Manual for the laboratory diagnosis and virological. Influenza epidemiology and influenza vaccine effectiveness.
Equine influenza ei is characterized by a very rapid spread and remains a disease with. Probable transmission routes of the influenza virus in a. This epidemiologic pattern reflects the changing nature of the antigenic properties of influenza viruses, and their subsequent spread depends upon multiple factors, including transmissibility. However, no comprehensive epidemiological analysis of global human cases of h5n1 from 1997 to 2015 exists. Avian influenza a h5n1 viruses have caused many, typically severe, human infections since the first human case was reported in 1997. Challenges of global surveillance during an influenza pandemic pdf, 678kb april 2011. Pdf the epidemiology of influenza and its control researchgate. Between 2003 and 2018, 860 cases were reported, with 454 deaths a case fatality rate of 53%. For all zoonotic avian influenza virus aiv serotypes except h5n1 and h7n9 for which methods have been previously described 3, we. It is a contagious respiratory illness caused by influenza viruses. Highly pathogenic avian influenza hpai h5n1 virus strains have infected poultry or wild birds in more than 50 countries since 2003. Gastrointestinal distress is also known to occur should the virus spread to the stomach.
Moreover, few studies have examined in detail the changing epidemiology of human h5n1 cases in egypt, especially given the outbreaks since november, 2014. Epidemiology and pathogenesis of influenza journal of. An executive summary in english provides an overview of the noteworthy developments and events in influenza epidemiology of the season before. The equine influenza virus eiv is a major pathogen of respiratory diseases in horses, donkeys and mules. Risk factors for severe outcomes following 2009 influenza a h1n1 infection. Flu can cause mild to severe illness, and at times can lead to death. Epidemiology and illness severity of pandemic h1n1 09 virus. Sixteen countries have reported detection of cases of human hpai h5n1 virus infection since 2003. Epidemiology, microbiology, and treatment considerations. Epidemiology of human infections with avian influenza a.
The epidemiological pattern of influenza over the past century is outlined. The relation of the concentration of unadapted and adapted influenza virus in the mouse lung to the death or survival of the infected host. The laboratory diagnosis and virological surveillance of influenza 27 2. In commemoration of the centennial of the 1918 influenza pandemic, the american journal of epidemiology has convened a collection of 12 articles that further illuminate the epidemiology of that pandemic and consider whether we would be more prepared if an equally deadly influenza virus were to emerge again. An overview of the epidemiology and emergence of influenza. Epidemiology of avian influenza h7n9 outbreak in china n engl j med 370. Influenza morbidity caused by 2009 pandemic h1n1 virus remained above seasonal baselines throughout spring and summer 2009 and was the cause of the first influenza pandemic since 1968. H2n2 also occurs when an influenza a subtype from animals emerges that is different from the same subtype in humans results in little population immunity to the new novel virus. From time to time new strains emerge and cause global pandemics. However, the symptoms of the disease may persist in some form for up to. Thomas2 abstract influenza virus affects the respiratory tract by direct viral infection or by damage from the immune system response. An overview of the epidemiology and emergence of influenza a.
Influenza, an acute contagious respiratory infection caused by orthomyxoviruses a, b, and c, occurs in local outbreaks, epidemics and pandemics. The role of influenza in the epidemiology of pneumonia. Influenza flu epidemiology virginia department of health. Differences in the morphology and antigen patterns for these viruses account for the differences in virulence and immunity. Each type includes many different strains that tend to change from year to year. According to banning 20, the flu is no longer infectious after five to seven days. They provide details on the current vaccine strains, summarise the development of the viruses since the last report, and closely follow the main developments for the ongoing influenza season. Avian influenza a h5n1 virus infection epidemiology. Important changes in the timing of influenza epidemics in the who european.
Accounts for 80% of influenza infections of human each year all ages. In the united states, the pandemic was characterized by a substantial increase in influenza activity that was well beyond historical norms. In the present commentary, we place these 12 articles in the. In a longterm populationbased retrospective cohort study conducted in three metropolitan areas nashville, rochester, and cincinnati, hospitalization rates for children aged pdf, 459kb january 20. In humans, the respiratory epithelium is the only site where the hemagglutinin ha molecule is effectively. Influenza causes fever, cough, sore throat, nasal congestion, muscle pain, headaches, and fatigue. The report on the epidemiology of influenza in germany is published annually by the robert koch institute.
Many national and international health agencies recommended the use of face masks during the 2009 influenza a h1n1 pandemic. The tools of molecular epidemiology have been applied in an attempt to determine the origin of pandemic viruses and to understand what made them such successful pathogens. Influenza is an important cause of outpatient medical visits and hospitalizations among young children. This is a prospective, active surveillance and hospitalbased epidemiological study to collect epidemiological data in the gihsn.
Face masks to prevent transmission of influenza virus. Report on the epidemiology of influenza in germany. In birds, the natural hosts of influenza, the virus causes gastrointestinal infection and is. The influenza virus characterisation reports give an overview of circulating influenza viruses in europe. Epidemiology as related to the phylogenetic analysis of the evolution of the influenza virus mtbi0203m amanda criner1,brandon hale2, lorena moralesparedes3, david roy estrella segura4, and ariel cintronarias5 1 department of mathematics, university of maine, orono, me 2 departments of mathematics and biology, murray state university, murray, ky. Once ai is established in domestic poultry, it is a highly contagious disease and wild birds are no longer an essential ingredient for spread. Seasonal influenza annual epidemiological report for. Virus and disease, epidemics and pandemics steinhoff. The h5n1 virus is considered as a serious pandemic threat which has potentially to reendemic over time. Interactions arising from sequential viral and bacterial infections play important roles in the epidemiological outcome of many respiratory pathogens.
Get a printable copy pdf file of the complete article 2. Preliminary epidemiology of human infections with highly. The global influenza hospital surveillance network gihsn aims to determine the burden of severe influenza disease and influenza vaccine effectiveness ive. We prospectively estimated effect of travel on influenza epidemiology sannemeike belderok, guus f. In the 20162017 influenza season, 15 sites in 14 countries participated in the gihsn. The infection of humans with an h5 avian influenza virus in hong kong in 1997 has resulted in a reconsideration of the role of the avian species in the epidemiology of human influenza. A collection, storage and transport of specimens 29 2. The epidemics caused by the influenza virus are estimated to result in about 3 to 5 million cases of severe. Global epidemiology of avian influenza a h5n1 virus. Influenza a, b and c all have a segmented genome, although only certain influenza a subtypes and. Characterizing the epidemiology of the 2009 influenza a. Postinfluenza bacterial pneumonia continues to play a significant role in the morbidity and mortality associated with both seasonal and pandemic influenza virus illness. Probable transmission routes of the influenza virus in a nosocomial outbreak volume 146 issue 9 s. We searched publications using the scopus database, and grey literature using the world health organisations who, centres for disease control and prevention cdc, flutrackers and promed.
Influenza a, therefore, is the most clinically important of the three viruses, responsible for both epidemics and pandemics. Epidemiology as related to the phylogenetic analysis of. Infectivity of influenza depends on the cleavage of ha by specific host proteases, whereas na is involved in the release of progeny virions from the cell surface and prevents clumping of newly formed virus. This study aims to investigate the distribution, prevalence, an d transmission of avian influenza virus h5n1 in sumatera. Influenza viruses circulate around the world every year. Abstract pandemics are the most dramatic presentation of influenza. Influenza occurs in distinct outbreaks of varying extent every year.
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