Drivers of the Emergence of Viral Diseases in Humans - Essay Example

? Drivers of emergence of viral diseases in humans Introduction The past few decades have witnessed anincreased interest in the upsurge in the number of viruses causing unanticipated sicknesses and spates among people, livestock and wildlife. In many instances, the outbreaks have severely strained both the local and national resources during periods when health care expenditure in the economically developed states has been restrained. Emerging illness is a phrase that has been utilized with augmenting occurrence to delineate the appearance of an unidentified contagion, or a beforehand identified contagion that expanded to a new ecological niche or a geographical area (Howard & Fletcher, 2012). The primary meaning is that these are representative of continually surfacing contagions reacting to speedy changes in the association between host and the pathogens. Current literature has identified that there are almost 1, 400 species of human pathogens. Almost 60 percent of these pathogens are zoonotic. This implies that almost 60 percent of the pathogens are infections that are transmitted between humans and vertebrates. In reference to Woolhouse et al (2012), emerging and re-emerging pathogens are most probable to be zoonotic. Viruses form a majority of this group. In addition, viruses with RNA sequences constitutes a third of all emerging and re-emerging contagions. Emergent pathogens are characteristically those with a wide host variety ranging across numerous mammalian animals. In the contemporary world, in spite of the exceptional progresses towards development of steps to counter the development of the infectious illnesses, the increased global mutuality, increased world travel and climate change have contributed deposits of complication to controlling and containing these contagious diseases that not only have an impact on an individual’s health but also a nation’s economy. Severe acute respiratory syndrome (SARS), HIV AIDS, and the H1N1 influenza are some of the examples of emergent contagious diseases in the contemporary world (Howard, 2012). Chronological data in addition to microbial ascertaining and phylogenetic structures indicate that contagious illnesses have been developing over the past 5 decades and this emergence has been contributed by numerous factors. Remarkably, most of the illnesses originate from animals such as rodents and bats, as shown by the presence of Nipah virus encephalitis, lassa fever and hantavirus pulmonary syndrome (Howard & Fletcher, 2012). Current interest in emerging contagions has centered on three primary fields. First, it has centered on how the interaction of the environment, human societal pressures and climate can cause unanticipated outbursts of emergent illnesses. Second, it has centered on the apprehension on how viruses can be transmitted from a reservoir to a host, and thirdly on recognizing the elements of the illness process that present opportunities for treatment and prevention. Drivers of Emerging Viral Diseases in Humans i. Animals that act as reservoirs of Human diseases Many emerging illnesses arise when transferable agents in animals are passed to people. The advent of agriculture 10, 000 years ago was one of the primary factors that contributed to the rise of majority of the infections in the present world. Agricultural activities drove people near wild animals and livestock. Notably, people put establishments in these regions (Lashley $ Durham, 2007). This offered a fertile ground for the transmission of infections from the animals to humans. Among the mammalian species, members that make up Muridae family have been the natural hosts of Hantaviruses and arenaviruses. The mamals reproduce faster and increase the population’s exposure and risk to the pathogens. Additionally, domestic livestock have also contributed to the spread and emergence of virus infections. For instance, pigs have been associated with numerous outbursts of emerging infections. A total number of 265 cases of viral infections associated with pigs were reported in Malaysian states. Additionally, 11 cases of infections were reported in 1999 among abattoir employees who handled pig carcasses. Regular interaction of people with animals such as cats, dogs and horses, offer an additional opportunity for the transfer of animal illnesses to humans. Though these animals have been kept in the households for long, there have been few cases of transmission of infections (Pasrish et al, 2008). Another example of a zoonotic infection is the Influenza. Its origin can be associated with the ancient pig-duck farming in China. Strains inducing the frequent biennial outbursts result from an assortment of the influenza strains to generate a new virus that infests people. Evidence obtained Webster et al (200o) shows that ducks and waterfowl are the primary reservoirs of influenza virus. Additionally, the virus is present in pigs, which act as a mixing vessel for the new mammalian influenza strains. According to Morse and Schluederberg (1990), the rearing of pigs and ducks puts the two classes of animals in contact and offer a natural laboratory for the generation of new influenza recombinants. ii. Molecular basis of cross-species transmission Viruses must attach themselves to other sensory receptors on the surface of the host cell in order to move in and contaminate the cells. New diseases can result from the viruses’ evolution of their aptitude to attach to either a different cell receptor in a new target host, or utilize the homologue of a subsisting receptor cells in new classes (Morse, 2005). In 2002, there was an outburst of SARS coronavirus that happened in China and extended to people in more than 35 other nations. The SARS-CoV infected people in southern China had obtained the virus from Himalayan Civets and rocoon dogs (Parrish et al, 2008). Evidence shows that some of these infections were cross-transmitted in the wet market of Guangzhou. In order to contaminate people, SARS-CoV attaches itself to the angiotensin-changing enzyme 2 receptor. Influenza can arise in new hosts through adjustment of the superficial haemaglutinin constructs to receptors on the novel host plasma membrane (Woodhouse $ Gowtage-Sequeria, 2005). Influenza A viruses are available among aquatic birds, which bind on the sialic acid deposits on the surface of human and avian cells. Nonetheless, avian influenza viruses have an immense attraction towards sialic acid associated to the galactose unit through ?2–3 link. On the other hand, the human influenza viruses have an immense attraction towards sialic acid associated through ?2–6 bond (Webster et al, 2000). This is a replication of the pathology of birds where the primary host organ is the gastrointestinal tract while in humans is the respiratory tract with sialic acid dominant with ?2–6 bonds. iii. Human Behavior and Ecological factors Interaction between the hosts and the transmitter is a prerequisite for virus transmission and is therefore influenced by the geographical and behavioral separation of the transmitter and the recipient hosts (Parrish et al, 2008). Aspects that influence geographical transmission of host species or that diminishes their interactive split-up are inclined to enhance viral emergence. Parrish et al (2008) denote that human-prompted alterations may encourage viral host switching from animal to humans, including alterations in demographic and social aspects such as travel, in human behavior such as sexual contacts and practices and farming practices and in the environment such as deforestation and agricultural growth. The density of the receiver host population is fundamental in the transfer and widespread likelihood of any transmitted virus (Morse, 2005). Human trade patterns and travel has been identified as one of the behaviors of people that contribute to the emergence of significant viruses. Air travel offers a primary danger to the health of people through the spread of new contagious agents. World Health Organization estimates that more than 90 million air travels are made annually. This makes it possible for an individual to visit numerous nations and continents in several hours (Hosseini et al, 2010). This is different from what happened in the past, people did not have access to many parts of the world within such a limited period. Reports now indicate that regular air travel is a primary contributing aspect of the emergence and reemergence of infections. This is clearly shown by an examination of the speedy spread of SARS virus in 2003, when the contagion originated from China to 18 other nations in just a week (Fidler, 2008). Road transport also presents another way of transmission of an infectious disease. There are high number of passengers that travel from one state to another in Europe and United states. These people may bring the virus to their destination and contribute to the spread and emergence of a contagious disease. Notably, it is not only people that travel but also other animals. It is estimated that almost 100 thousand wild-caught animals are carried through air annually, most of them being placed in holding accommodations near inhabited areas while on transit. This includes mosquitoes. According to Roehrig et al (2002), the West Nile Virus emerged in United States in 1999 when an infested mosquito survived the long air flight from Middle East to New York City. The spread of West Nile Virus in United States portrays the spread of a virus to a region with contagion-efficient transmitters. Ecological contacts can be multifaceted, with numerous factors working in collaboration or in a system. For instance, movement of population from rural areas to urban centers can spread a localized contagion (Askar et al, 2012). The pressure on infrastructure in the congested and fast growing urban centers may slow health procedures, and therefore, allowing the establishment of new infections. These cities also offer an ample ground for the spread of viruses such as HIV. HIV appears to have a zoonotic origin (Myers et al, 2004). The ecological aspects that would have allowed exposure of people to the natural host with the virus that was antecedent to HIV-1 were contributory in the spread of the virus among people (Wain et al, 2007). Patterns of host interaction and density seem to have a significant effect on disease emergence. For instance, Simian immunodeficiency viruses (SIV) are usual in the ancient world primates are probable to have triggered many dead-end zoonotic contagions in the past. However, the split-up of SIV-infested primates in the forests of Central Africa from people probably reduced and restricted the transmission of the virus. In order to develop, HIV probably needed not only genetic alterations to bestow human adjustment, which was partly finished in transitional hosts, but also enable alterations in human conduct. For HIV, Myers et al (2004) notes that the long period of contagion presented it with numerous opportunities to be transferred and to take advantage of numerous human behaviors such as sexual intercourse and drug use. Notably, human behavior has significant effects on the spread of virus causing agents. These behaviors have led to human to human infections. iv. Climate Change The environment is shifting on an extraordinary measure. The most prominent indicators of climate change have been the snowballing climatic conditions caused by changes in sea surface temperatures in the pacific referred as El Nino Southern Oscillation. An El Nino occurrence happened in numerous regions in America in 1990 and caused a protracted drought that caused the rise of Hantavirus pulmonary syndrome (Howard & Fletcher, 2012). On the contrary, an unexpected change in sea temperatures in 1995 caused heavy rainfall in Columbia and resulted to re-emergence of mosquito-borne illnesses such as equine encephalitis and dengue (Wearing & Rohani, 2006, Lambrechts et al, 2011). Vector-borne illnesses are deemed as extremely subtle to climatic conditions. Notably, a minor postponement of a transmission season may have adverse effects on the transmission rates. Climate change can result to transformed vector dispersals if appropriate regions for extension become freshly present. The impact may be uneven if the vector transfers illness to people or animals devoid of pre-existing levels of learned resistance with the outcome that the clinical cases are various and hypothetically adverse (Howard & Fletcher, 2012). Up surge in temperatures and seasonal variations in either rainfall or temperature favor the transmission of vector-borne illnesses to high altitudes and to temperate latitudes. The persistent change imposed by people on habitats under the pretext of progress has had an effect on the population of rodent habitats (Githeko et al, 2000). Epidemics of Hantavirus pulmonary syndrome in United States and Bolivian Hemorrhagic fever in Bolivia have been linked with irregular seasons of rainfall or drought that led to the irregular increase in the number of rodents. Minor climatic changes can result to a considerable change in the number of rodent populations in the different regions. An elongated drought season in the 1990’s in United States resulted to a decrease in the number of rodent eaters and in turn resulted to an increase in the number of rodents (Fidler, 2008). Because of human encroachment and development of rail and infrastructure, the population of forests has decreased significantly, especially in the Amazonian basin and regions of Southeast Asia. This has had considerable impact on the local ecosystems by straining the range of natural predators’ contributory in the controlling potential vectors such as insects and rodents (Lashley & Durham, 2007). v. Microbial Adaptation and change Acquired resistance of pathogens to antimicrobial medicines has contributed to the re-emergence of diseases. Microbes, similar to other living things, are continually evolving. The development of antibiotic-resistant microbes due to the omnipresence of antimicrobials in the surroundings is an evolutionary example on bacterial adjustment, in addition to an illustration of the power of natural selection (Howard & Fletcher, 2012). Assortment for antibiotic-resistant microbes and drug-resistant pathogens has become regular, being motivated by the broad and unsuitable usage of antimicrobial drugs in numerous applications. Numerous viruses portray a high transformation rate and can speedily change to result to new variants. An outstanding example is influenza (Morse & Schluederberg, 1990). Frequent yearly outbursts are triggered by “antigenic drift” in a preceding flowing influenza strain. An alteration in an antigenic position of a superficial protein, frequently the hemagglutinin protein, permits the novel variant to re-infect formerly infested people since the changed antigen is not instantly identified by the immune system. On infrequent instances, the evolution of a new variant may lead to a new manifestation of disease. An example of new manifestation of an illness is the widespread of Brazilian purpuric fever in 1990, linked to a newly developed clonal variant of Hemophilus influenzae (Morse & Schluederberg, 1990). Conclusion Emergence of new transmittable illnesses is not a novel spectacle. Almost 60 to 80 percent of all human pathogens are identified as zoonotic. Certainly, scientists have identified that viruses signify the highest percentage of biomass on earth. Viruses can transform and evolve rapidly than mammals. Therefore, the emergence of vector-borne illnesses denotes a primary threat in the short run. A primary apprehension, detection, characterization and reaction to the danger of emerging and re-emerging contagions are the interconnection of contacts between humans, animals and other infectious living things. The emergence and re-emergence of viral infections is caused by the movement of people, urbanization, microbial adaptation and alterations and climate change. It is imperative to consider these factors in order to devise mechanisms on prevention and control. References Askar, M.A, Mohr. O, Eckmanns T., Krause, G., Poggensee G. 2012. Quantitative assessment of passenger flows in Europe and its implications for tracing contacts of infectious passengers. Euro Surveill (17): 20195. Center for Disease Control 2008. Globalization, International Law, and Emerging Infectious Diseases. Emerging Infectious Diseases, 10(2), 1-20. 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