Pandemic Influenza: Potential Contribution to Disease Burden

Journal of the Formosan Medical Association, 2006

Influenza A virus is well known for its capability for genetic changes either through antigen drift or antigen shift. Antigen shift is derived from reassortment of gene segments between viruses, and may result in an antigenically novel virus that is capable of causing a worldwide pandemic. As we trace backwards through the history of influenza pandemics, a repeating pattern can be observed, namely, a limited wave in the first year followed by global spread in the following year. In the 20 th century alone, there were three overwhelming pandemics, in 1918, 1957 and 1968, caused by H1N1 (Spanish flu), H2N2 (Asian flu) and H3N2 (Hong Kong flu), respectively. In 1957 and 1968, excess mortality was noted in infants, the elderly and persons with chronic diseases, similar to what occurred during interpandemic periods. In 1918, there was one distinct peak of excess death in young adults aged between 20 and 40 years old; leukopenia and hemorrhage were prominent features. Acute pulmonary edema and hemorrhagic pneumonia contributed to rapidly lethal outcome in young adults. Autopsies disclosed multiple-organ involvement, including pericarditis, myocarditis, hepatitis and splenomegaly. These findings are, in part, consistent with clinical manifestations of human infection with avian influenza A H5N1 virus, in which reactive hemophagocytic syndrome was a characteristic pathologic finding that accounted for pancytopenia, abnormal liver function and multiple organ failure. All the elements of an impending pandemic are in place. Unless effective measures are implemented, we will likely observe a pandemic in the coming seasons. Host immune response plays a crucial role in disease caused by newly emerged influenza virus, such as the 1918 pandemic strain and the recent avian H5N1 strain. Sustained activation of lymphocytes and macrophages after infection results in massive cytokine response, thus leading to severe systemic inflammation. Further investigations into how the virus interacts with the host's immune system will be helpful in guiding future therapeutic strategies in facing influenza pandemics. [J Formos Med Assoc 2006;105(1):1-6]

2004

Viruses and Viral Infections in Developing Countries, 2020

Cell, 2005

Influenza Vaccines for the Future, 2010

In this chapter, we highlight how recent advances in influenza epidemiology can inform strategies for disease control. Given the challenge of direct measurement, influenza epidemiology has benefited greatly from statistical inference from the analysis of large datasets regarding hospitalization, mortality, and outpatient visits associated with seasonal circulation of influenza viruses. These data have allowed comparison of the impact of influenza in various climates and the evaluation of the direct and indirect benefits of vaccination, the latter through the vaccination of "transmitter populations" such as school children, to achieve herd immunity. Moreover, the resolution of influenza epidemiology has undergone a leap to the molecular level due to the integration of new antigenic and viral genomic data with classical epidemiological indicators. Finally, the new data have led to an infusion of quantitative studies from the fields of evolutionary biology, population genetics, and mathematics. Molecular influenza epidemiology is providing deeper insight into temporal/spatial patterns of viruses, the important role of reassortment in generating genetic novelty, and global diffusion of virus variants -including the role of the tropics, as a source of new variants. Higher resolution, contemporary, and historic epidemiological data provide a more detailed picture of the effect of age and other host characteristics on outcomes, as well as better estimates of the transmissibility of pandemic and seasonal influenza viruses. New epidemiologic and virologic data from the current A/H1N1pdm 2009 pandemic improve our understanding of the emergence and establishment of new viral subtypes in

Indian Journal of Microbiology, 2009

“Survival of the fittest” is an old axiom laid down by the great evolutionist Charles Darwin and microorganisms seem to have exploited this statement to a great extent. The ability of viruses to adapt themselves to the changing environment has made it possible to inhabit itself in this vast world for the past millions of years. Experts are well versed with the fact that influenza viruses have the capability to trade genetic components from one to the other within animal and human population. In mid April 2009, the Centers for Disease Control and Prevention and the World Health Organization had recognized a dramatic increase in number of influenza cases. These current 2009 infections were found to be caused by a new strain of influenza type A H1N1 virus which is a re-assortment of several strains of influenza viruses commonly infecting human, avian, and swine population. This evolution is quite dependent on swine population which acts as a main reservoir for the reassortment event in virus. With the current rate of progress and the efforts of heath authorities worldwide, we have still not lost the race against fighting this virus. This article gives an insight to the probable source of origin and the evolutionary progress it has gone through that makes it a potential threat in the future, the current scenario and the possible measures that may be explored to further strengthen the war against pandemic.

Influenza epidemics occur regularly and prediction of their conversion to pandemics and their impact is difficult. Coordination of efforts on a global scale to control or reduce the impact is fraught with potential for under and overreaction. In light of the 1956 pandemic and more recently the SARS and H1N1 pandemics, the public health community took steps toward strengthening global surveillance and a coordinated response in keeping with the continuing memory of the tragedy seen in 1918. The scientific, professional, and technical resources of the 21st century are now advanced far beyond those then available. The H1N1 pandemic which commenced in 2009 progressed differently than predicted; its course was difficult to predict with any degree of certainty. Public responses to national immunization programs against the H1N1 virus have been weak. International movement of diseases can lead to creation of new endemic areas and continuous spread such as that which happened with West Nile ...

Future Virology, 2013

Vaccine, 1999

Biotechnology Journal, 2006