The Next Influenza Pandemic - Essay Example

THE NEXT INFLUENZA PANDEMIC 2006 INTRODUCTION A pandemic is a global disease outbreak. A flu pandemic takes place when a new influenza virus emerges for which people have little or no immunity, and for which there is no vaccine. An influenza pandemic occurs when a new subtype emerges that has not formerly circulated in humans. The disease spreads easily person-to-person, cause serious illness, and can sweep across the country and around the world in very little time. This research explained what Influenza Pandemic means and categorized the three types of Influenza which are the Type A, Type B, and Type C Influenza. The research explained how the next influenza pandemic may arise and its possible outcome. This paper also discussed the history of Influenza happened in the year 1918, 1957, and 1968. Moreover this research used pictures and tables for effective illustrations of significant information. GENERAL DISCUSSION An influenza pandemic is a universal outbreak of flu disease that takes place when a new type of influenza virus appears that people have not been exposed to before (Kilbourne ED. 1975). According to Kilbourne ED. (1975) that pandemic flu is a worldwide outbreak of disease that takes place as soon as a new influenza virus appears in humans, causes serious illness and then spreads effortlessly from person to person worldwide. There are three types of influenza. Influenza A, B and C viruses are known to cause disease in humans. While influenza B and C viruses are strictly human pathogens, influenza Type A viruses are readily isolated from avian species, pigs and other animals. Influenza Type A viruses are divided into subtypes based on differences in the surface glycoprotein antigens, hem agglutinin (HA) and neuraminidase (NA). There are 14 known HA subtypes and 9 known NA subtypes. All of these subtypes have been isolated in birds but only 3 different HA and two different NA subtypes have been isolated in humans (See table bellow) Table : Influenza Subtypes Host HA Subtypes NA subtypes Humans H1, H2, H3 N1, N2 Birds H1 - H14 N1-N9 The influenza viruses are only one of its kinds amongst the respiratory viruses in that they undergo major antigenic variation (Stuart-Harris C. 1979). Antigenic drift entails minor antigen changes from one season to the next and may result in epidemic spread of the new strain. Antigenic shift entails major antigenic changes of the HA and NA molecules and happens merely with Influenza A viruses. These changes can result in the appearance of pandemic viruses. In accordance with Stuart-Harris C. (1979) three worldwide outbreaks of influenza occurred in the 20th century: in 1918, 1957, and 1968. Of these, the 1918 Spanish Flu was the most severe, with 50 million or more deaths worldwide. The last 2 were in the era of modern virology and most thoroughly characterized. All 3 have been unofficially identified by the presumed sites of origin as Spanish, Asian, and Hong Kong influenza, respectively. According to Stuart-Harris C. (1979) they are now identified to represent 3 various antigenic subtypes of influenza Type A virus: H1N1, H2N2, and H3N2, respectively. Not classified as true pandemics are 3 prominent epidemics: a pseudo pandemic in 1947 with low death rates, an epidemic in 1977 that was a pandemic in children, and an abortive epidemic of swine influenza in 1976 that was feared to have pandemic potential. Major influenza epidemics show no predictable periodicity or pattern, and all differ from one another. Evidence implies that true pandemics with changes in hem agglutinin subtypes take place from genetic reassortment with animal influenza Type A viruses. No one can foresee when a pandemic might take place, but public health experts think it is only a matter of time before the next one arises. Experts all over the world are watching the H5N1 avian flu condition in Asia very severely and are preparing for the probability that the virus may start to spread more easily and broadly from person to person. If this happens, the next pandemic could start very soon, or it may take quite a few years for a pandemic flu virus to build up and start spreading worldwide. Pandemic influenza may arise through at least 2 mechanisms Reassortment between an animal influenza virus and a human influenza virus that produces a new virus: a key event would perhaps be a change in the binding specificity of the virus from a receptor in the lower respiratory tract to one in the upper respiratory tract. This may outcome in a decrease in at least the initial pathogenicity, as the infection would be more probably to begin with a tracheal bronchitis rather than pneumonia. Additionally, if human adaptation resulted from reassortment with a human virus, pathogenicity factors on gene segments not in the resulting reassortment would be missing and there may be a degree of prior immunity in the population to the human virus derived gene segments, both further reducing pathogenicity in humans. Direct spread and adaptation of a virus from animals to humans: pandemic strains of influenza Type A virus take place by genetic reassortment between avian and human viruses: pigs could provide as mixing vessels for such reassortment events. Following the outbreaks of group A subtype H5N1 (A/H5N1) avian influenza viruses in Hong Kong in 1997, in which 6 people died, the hypothesis was put forward that not only pigs but also humans themselves might serve as mixing vessels for the next pandemic influenza virus. It should be kept in mind also that the mixing vessel hypothesis is no more than a hypothesis, and the part of pigs as mixing vessels has not been established clearly. Genetic reassortment between avian and human influenza Type A viruses in Italian Sus scrofa happened at some time between 1983 and 1985: human-like H3N2 strains isolated from 1985 to 1989 contained the internal protein genes of avian-like H1N1 viruses, while those isolated in 1977 and 1983 did not. Multiple genetic reassortment of avian and human influenza Type A viruses in European Sus scrofa, resulting in the appearance of an H1N2 virus of novel genotype, the evolution of human influenza viruses. Avian-to-human transmission of the PB1 gene of influenza A viruses in the 1957 and 1968 pandemics. Emergence of influenza A viruses. Once a totally contagious virus comes out, its worldwide spread is considered unavoidable. Countries might, through measures such as border closures and travel restrictions, delay arrival of the virus, but cannot stop it. The pandemics of the previous century encircled the globe in 6 to 9 months, even when most international travel was by ship. Given the speed and volume of international air travel today, the virus could multiply more rapidly, possibly reaching all continents in less than 3 months. CONCLUSION It is complicated to foresee when the next influenza pandemic will take place or how severe it will be. Wherever and whenever a pandemic starts, everybody all over the world is at risk. Countries might, throughout measures such as border closures and travel limitations, delay appearance of the virus, but cannot stop it. Influenza epidemics take place at one to three year intervals generally in the late fall. Annual inoculations with the current influenza vaccine for that particular year must be administered to all high risk children and adults as well as health care professionals, where it has been shown to particularly reduce both morbidity and mortality. If physicians were more doing well at vaccinating high risk individuals, than the current annual 10% rate for children and 40% rate for adults then people would be much better prepared for the next unpredictable pandemic which could come as soon. People can get ready, but with the realization that no amount of hand-washing, hand wringing, public education, or gauze masks will do the trick. The keystone of influenza prevention is vaccination. It is irrational to think that people can count on prophylaxis with antiviral agents to guard a large, susceptible population for more than a few days at a time, and that is not long enough. But vaccination against what People do not know. Maybe against H5N1. But do we not by now have a vaccine No, we do not; no vaccine of enough antigenic potency is available in sufficient supply. The nature of the next pandemic virus cannot be foreseen, but that it will take place from 1 of the 16 known HA subtypes in avian or mammalian species. Therefore, preparation by genetic reassortment of high-yield seed viruses of all HA subtypes should carry on as soon as possible for potential use in vaccine production. REFERENCE Stuart-Harris C. (1979). Epidemiology of influenza in man. Br Med Bull;35:3-8. Kilbourne ED. (1975). The predictable natural disaster [op. ed.]. New York Times. Read More