Viral Disease Emergence and Spread in Humans - Assignment Example

Viral Disease Emergence and Spread in Humans Contents Contents 1 Introduction 1 Processes involved in emerging viral diseases 2 Epstein Barr Virus: An emerging pathogen 6 Conclusion 8 References 9 Introduction With the passing time, new pathological conditions and diseases have been identified. Epidemics of many diseases are on the rise and many health programs are launched by different organizations across the world but not all diseases have been eradicated from the world map apart from small pox (Levinson 2008). Emerging diseases are those pathological conditions that both did not exist previously and have emerged in a particular group or they are pathologies that have been rising and their prevalence is increasing. Viral disease emergence hence implies the pathologies that result due to viruses. These emerging viruses can be traced to their reasons of causation which are mainly previous viruses in the human beings as well as humans which have been given favourable chances to grow and lead to disease in groups. This is referred to as viral traffic (Morse 1997). Many reasons can be associated with the rise in the emergence of pathologies. These include changes in the environment and the living of the people (Domingo 2010; Morse 1997; Robins et al 2005). The dietary habits of the people are also a contributing factor which affects these emerging viruses (Morse 1997). The new discovery of viruses along with the other favourable reasons have led to the increase in many conditions and increased disease frequency associated with these viruses. Human immunodeficiency virus is the most common example. With the rise in the number of homosexuals, the spread of this disease has become more and approximately 50 percent of the new cases are actually homosexuals (Robbins et al 2005). This virus has been recognized since the year 1983 and has been on the spread (Lederberg 1997). West Nile virus which results in paralysing the person is another emerging virus which was discovered in the year 2002 (Robbins et al 2005). These are examples for new emerging diseases in the human population. Another aspect is the re appearance of certain diseases or the increase in the spread of a disease. H1N1 influenza serves to be an example. This disease led to a very large outbreak in the year 1918 and led to the deaths of 50 million people (Zimmer and Burke 2009). There were minor occurrences after this but another major outbreak occurred in the year 2009 when the disease developed as a pandemic affecting many countries in the world. Changes in the structure of the virus were noted in the new outbreak. Hence, this was an emerging disease which reappeared and served to affect many people (Gallher 2009). The H1N1 influenza virus explains that changes in the genetic makeup of the viruses can result in the emergence of disease (Domingo 2010). This paper will serve towards explaining the processes and factors involved in viral disease emergence and will be supported with the examples of specific emerging viruses. Processes involved in emerging viral diseases There are many processes involved in the emerging viral diseases. To begin with, 80 percent of the emerging viral diseases have been classified as originating from wildlife that is they are zoonoses (Ragaini 2006). The increase in the population of the world has resulted in the emergence of certain viruses as this has led to the intrusion into areas occupied by animals. Ross River virus has been a disease due to this intrusion. It is also seen that this intrusion can be counted as a reason of Human immunodeficiency virus and Ebola virus in Africa. With the increase in the human population, the area of land occupied by the animal’s decreases and a larger number of animals live in smaller areas which results in increased spread of disease between them due to the increased density (Morse 1993; Daszak 2000). Another important factor is that there is international export and import of animals from different countries in today’s world (Daszak 2000). A study also supported this aspect by presenting a molecular study which clearly showed the fact that a strain of herpes virus which is actually latent and does not lead to disease in African elephants, does not present similar characteristics in its Asian counterpart. It was seen that the similar strain could be fatal and disease causing in the Asian elephants (Richman et al 1999). The H1N1 virus is another example which showed a worldwide pattern with cases being reported from the Soviet Union, China and Hong Kong in the year 1977. This was linked to the international movement of pigs which resulted in the transfer of the virus from one area of the world to another (Zimmer and Burke 2009). This upholds the fact that the movement of infected animals and alteration of geographical location can lead to the spread of disease. It has also been seen that alterations in the climate of the globe has been favorable for certain insects in particular mosquitoes which has resulted in increase in their populations. Climatic changes are indicated by events like El Nino Southern Oscillation and floods. This increase has then led to the spread of diseases like dengue and malaria (Daszak 2000). The next important factor which has often been underrated and studied is that of the role of nutrition in the causation of viral emergence and diseases. A healthy and well balanced nutrition is extremely important and health is substantially improved with healthy intake of diet which consists of all the essential nutrients. A very good example is that of rotavirus which can prove be lethal and dangerous for children who do not receive proper nutrition. Deficiency of essential dietary substances can result in the decreased efficacy of the immunity in people and hence these people are vulnerable to contract diseases (Morse 1997). Research conducted by Beck and his colleagues also assists in upholding the role of nutrition in the spread of viral disease. It was a research conducted on mice that were deficient in selenium and vitamin E. When they were injected with a coxsackievirus B3 isolate which was weak and not disease causing, this virus developed into a strong and disease causing strain. The underlying principle to this was not understood but a definitive link between the nutritional deficiencies and this could be established (Beck 1997). Thus nutrition can also be counted as a factor. Advancements and changes in the field of agriculture have also contributed to the emergence of viral diseases. Hantaan virus is a very good example to support this factor. Basically this virus affects Apodemus agrarius which is a mouse that is very common in the lands where rice is cultivated. It leads to a hemorrhagic fever which is referred to as Korean hemorrhagic fever and it affects a large number of people in China with 100,000 people reporting with the infection annually. As this virus is found in the lands, the crop growers are the most vulnerable groups as they develop contact with these animals. Argentine hemorrhagic fever which is led to by the virus known as Junín virus is also an example of this. There was the emergence of a species of rodent on the lands on which maize plantation was started and this rodent was the carrier of this virus and hence served to infect people (Johnson 1993). Another important impact is that the combination of two animals for agriculture which include the usage of pigs and ducks in agriculture is China. This is an agricultural system which goes on in China and is used for producing food with better results. It can serve to lead to the production of strains of influenza viruses due to the contact between the duck and the pigs which are both carriers of strains of influenza. Hence this also leads to the emergence of virulent disease (Webster et al 1992). Many emerging viral diseases are waterborne as well. Still water serves to lead to an increase in the mosquitoes and mosquitoes are important carriers of many emerging diseases. This is also indirectly associated with agriculture because it is for agricultural purposes that dams are built and other storage reservoirs where this water stands for long periods. An example of lethal diseases that are spread by mosquitoes is Japanese encephalitis which is a cause of 7000 fatalities in the continent of Asia. It results due to the standing water that is poured into the fields of rice and hence serves as a ground for mosquitoes to multiply (Monath 1993; Morse 1995). Rift valley virus is another example and a very famous epidemic occurred due to this disease adjacent to Senegal River on which many dams are constructed in the area of Mauritania (Morse 1995). Certain natural environmental changes can also lead to the emergence of viral diseases. Changes in the climatic conditions can serve to provide for increase in the epidemics due to certain viruses. In the year 1993, certain changes were observed in the climate which did not occur normally. This was the occurrence of not a very strong winter and spring. This resulted in increase in the rodents who were carriers of the Hanta virus and a large number of people were infected with this virus in the area (Levin et al 1993). The increase in urbanization resulting due to the movement of human beings from the villages to cities has been an additional contributing factor resulting in the emergence of viruses (Morse 1995; Morse 1997). The United Nations provided an approximation that in the year 2025, 65 percent of the population around the world would be in the urban areas of the world (United Nations 1991). The human immunodeficiency virus is the perfect example to support this process of viral emergence. With the movement of the people from the rural areas suffering from this disease to the cities, there was subsequent spread of this virus to the urban areas (Morse 1995; Morse 1997). Also the means of transportation like road links and railway tracks have served for the movement of mosquitoes and this was the way how dengue virus was multiplied and communicated to different areas in Thailand (Wellmer 1983). Another important reason associated with the appearance of viral diseases in the human beings is an aspect related with these microorganisms. Over time changes in the genetic structure of the viruses can result in new infecting agents and hence lead to emergence of viral diseases. The genetic processes involved include mutation in the genes or their recombination or certain transfer in the genetic components (Domingo 2010). The influenza virus serves as a good example in which genetic mutations result in new strains which then again lead to outbreak of diseases (Levinson 2008). Epstein Barr Virus: An emerging pathogen Introduction Epstein Barr virus is a DNA enveloped virus which is associated with many pathological conditions which include infectious mononucleosis, lymphomas of the B-cells including Burkitt’s lymphoma, malignant cancer of the nasopharynx as well as hairy leukoplakia (Levinson 2008 & Kumar et al 2005). This virus has been given this name after the discoverers of this virus who were Epstein and Barr. They separated this virus from a case of Burkitt lymphoma and hence this virus is now referred to as Epstein Barr virus (Rao 2004). This virus is considered to be increasing in rate associated with the greater number of people suffering from immunosuppression due to acquired immune deficiency syndrome. It results in skin conditions and cancers. Its rate can also be considered to be on the rise because it is transmitted via blood transfusions and organ transplants and these procedures are more common now than they were before (Jackson 2006). Transmission and epidemiology: The structure of the Epstein Barr virus is very closely related to the other DNA enveloped herpes viruses. The major difference lies in the antigens. Viral capsid antigen is the most significant amongst the antigens on the virus and it is this antigen which is of significance in diagnosis. Other antigens related to this virus include early antigens (EA), nuclear antigen (EBNA), viral membrane antigen and the lymphocyte determined membrane antigen. The main target of this virus is the lymphocytes in the body and in particular the B lymphocytes. If the disease is in a latent stage, the presence of the virus DNA is seen in the cytoplasm of the B lymphocytes which have been invaded by the virus (Levinson 2008). Epstein Barr virus is a virus which is known to be found all around the world. The disease is basically passed on through secretions of the oral and the nasal cavity. There are differing ages of infection in the developing and the developed nations. Approximately 90 percent of children up till the age of 6 years are infected with the disease in the developing nations. On the other hand, in the developed nations the infectivity is mainly seen in adolescents. When the infection occurs in young children, they do not report with any pathology and this is rather beneficial because it leads to immunization against infectious mononucleosis. On the other hand in adolescents, almost 50 percent of the cases reports with this pathology. In the United States of America, infectious mononucleosis is reported in 100,000 patients every year (Brooks et al 2004). Reasons for spread: Lack of treatment and the rise in the cases of immunosuppression can be counted as reasons for increase in the incidence of this virus. Epstein Barr virus is a virus against which no vaccine has been developed and hence there is no proper means of prevention against the virus. Another important fact is that there is also no proper anti viral medication against this virus. Acylovir is administered in the very serious pathologies resulting due to this virus (Levinson 2008 & Volk 1996). Acylovir does not have any proper effect against the infectious mononucleosis. It is only seen that this drug basically leads to decreasing the spread of the virus from the oropharynx but this is also limited till the period the drug is given and this activity subsides after discontinuation of the drug (Brooks et al 2004). Conclusion The emergence of viral diseases is a subject of importance because it has been associated with the outbreak of many diseases throughout the world. This emergence is basically the identification of either a new viral pathogen which leads to disease or an existing virus which starts to increase its spread and affects a greater number of people. There are many processes involved in the emergence of viral diseases. These include the effect of human nutrition on the spread of viral diseases. Other factors include the changes in agricultural patterns which include the building of dams where the still water serves as a reservoir for this emergence. International travelling as well as means of transportation and the movement of animals from one region to another are other causes which lead to the emergence of viral diseases. The movement and migration of people from the rural areas to the cities is another process involved. The alterations in the genetic structure of the viruses lead to new virulent strains which can also lead to new viral disease outbreaks. Thus, there are many processes involved in the emergence of viral diseases and it is important to understand these in order to prevent pandemics and the morbidity and mortality associated with these. References Top of Form BECK, M. A. (1997). Increased Virulence of Coxsackievirus B3 in Mice Due to Vitamin E or Selenium Deficiency. The Journal of Nutrition. 127, 966S. Bottom of Form Top of Form BROOKS, G. F., BUTEL, J. S., MORSE, S. A., & JAWETZ, E. (2004). Jawetz, Melnick, & Books/McGraw-Hill, Medical Pub. Division. Top of Form DASZAK P, CUNNINGHAM AA, & HYATT AD. (2000). 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