Infection Control - the Role of Epidemiology in the Modern World - Essay Example

? Question Nature of Mycobacterium tuberculosis There are many micro organisms which live in and out of human bodies. Whereas there would be those that are essential to health, there are some that cause diseases. Micro organisms refer to microscopic living things found in air, soil, water, rocks, plants and animals among many other places (Medzhitov 2007, p.2). While some of these inhabit hot temperature places, others would only survive in ice cold conditions; while others survive with oxygen, others do not need oxygen for survival. According to McKinley Health Centre (2008), the micro organism that causes tuberculosis is referred to as Mycobacterium tuberculosis. This discovery was made by Robert Koch, a renowned German scientist and physician in 1882 (Nobel Price 2012). It was referred to as white and consumption plague then because out of seven human beings dying, one had TB. More so, it carried away more than a third of the middle age group working force. The bacterium affects body organs such as kidneys, bones, brain and most commonly, the lungs resulting to pulmonary tuberculosis. Today, the International Union Against Tuberculosis and Lung Disease, IUATLD (2010) documents TB as a great problem, particularly in low income countries. It has been cited as the number one killer for people between the ages of 15 and 49 with Sridharan citing it as “the single leading cause of human mortality by an infectious disease claiming 3 million lives annually with an estimated 8 million cases arising every year” (2006, p.1). Tuberculosis would be caused when an individual inhales Mycobacterium tuberculosis which enters through the lungs, spreading to other body parts through the lymphatic system, airways, blood stream or through direct extension. IUATLD (2010, p.5) observed that 80% of tuberculosis forms would be the contagious pulmonary tuberculosis. On the other hand, extra-pulmonary tuberculosis affects organs other than lungs with lymph nodes, pleura, bones, joints, spine, nervous system, genitourinary tract and the abdomen being commonly infected. This would develop in two stages: initially as an infection and later as a disease, tuberculosis. Research studies by Edwards (2008) revealed that Mycobacterium tuberculosis exist as commensal flora in human body and would cause the development of diseases, especially rheumatoid arthritis. Similar studies by Kempsell et al. (2001) indicate that rheumatoid arthritis patients had commensal organisms such as Mycobacterium tuberculosis trafficked from other sites of the body. The surface of Mycobacterium tuberculosis is characterised by a waxy coating, particularly mycolic acid that makes the cell Gram staining impervious as it would neither be gram positive nor gram negative (Sridharan 2006). This is the reason for application of acid-fast techniques of detection and has been classified by Guiard et al. (2009) as acid-fast Gram positive form of bacteria because its cells do not have the outer cell membrane. The micro organism is highly aerobic thus requires high amounts of oxygen. The bacteria divides slowly compared to other bacteria. It is said to divide every 20 hours whereas other bacteria divide in minutes, such as Escherichia coli which divides every twenty minutes (Medzhitov 2007). This is a small bacillus and would resist weak disinfectants and survive under dry conditions for several weeks due to its lipid rich cell wall, a critical virulence factor. In the lungs, it would have alveolar microphages take it up but would not be digested. Again, its cell wall inhibits phagosome fusion with lysosome. According to Todar (2009), Mycobacterium tuberculosis would block early endosomal autoantigen 1, EEA1, a bridging molecule, which would however not prevent nutrient filled vesicles fusion. The bacteria would then multiply within the macrophage. Having carried UrecC gene, phagosome acidification would be inhibited. Similarly, it would evade the killing of macrophage by neutralising nitrogen intermediates that would be reactive. Method of transmission The probability of infecting other persons with tuberculosis would be determined by the bacterial load in lungs and the ability of the infected to spread the bacteria in the air. Pulmonary tuberculosis would be determined by use of a microscope in examination of sputum specimens. Those detected with infection, referred to as smear positive cases by Todar (2009), would be considered highly infectious. On the other hand, smear negative cases would be less severe and less infectious. Extra pulmonary cases would be almost never infectious. The infected patients would expel the tuberculosis micro organisms indirectly into the air while coughing, sneezing, laughing or talking. These would rapidly dry to “droplet nuclei” inhibiting the micro organisms that would be suspended in air for a long time (IUATLD 2010, p.6). When inhaled by any other persons, they get established in the lungs and multiply, hence a tuberculosis infection. Sunlight would rapidly destroy the microbes hence the importance of ensuring proper ventilation. Infection would be prevalent among those with long term contact with the infected. WHO (2012) also note that direct contact with infected bodies, even corpses would lead to tuberculosis infection. Centers for Disease Control and Prevention, CDCP (2005) noted that persons handling bodies are at risk of contacting TB through infectious aerosols. 90% of the infected never develop the disease unless their immunity is compromised. Prevention Health care institutions should initially and continuously conduct evaluations on transmission risk of Mycobacterium tuberculosis. This would guide on the kind of environmental, administrative and respiratory protection control to adopt (CDCP 2005). This would also be important in evaluating the quality of infection control and areas wanting in improvement. According to CDCP (2005, p.9), respiratory protection controls would be employed using respiratory protective equipment in cases of high risk of exposure. This further reduces the risk of infection in air contaminated by droplet nuclei expelled by infectious TB patients. This control goes hand in hand with training of health care workers and TB patients on cough etiquette and respiratory hygiene. Among these includes the importance of washing of hands before eating and after coughing so as to avoid transmitting the microbes or re-infecting oneself. Two types of isolation rooms have been used in controlling the spread of tuberculosis. Infectious isolation rooms would be maintained at negative pressure to inhibit exfiltration of infectious microbes from a patient in the room. Protective isolation rooms would be maintained at positive pressure to inhibit infiltration of infectious microbes hence protecting the patient in the room. Environmental controls could also be enforced to prevent and reduce the amount of infectious droplet nuclei in the air. Primary methods in this case include use of local exhaust ventilation such as tents and hoods and dilution and removal of contaminated air through general ventilation (CDCP 2005, p.8). Secondary controls would on the other hand call for controlling the airflow so as to inhibit contamination of areas near the source and cleaning the air through filtration, use of high efficiency particulate air, HEPA or Ultraviolet germicidal irradiation, UVGI. Question 2 A) Epidemiology and infectious disease The role of epidemiology in the modern world has increasingly become recognised. This study gives information on problems in public health and the causes of the same. Unlike a clinician who would focus on the health of an individual, epidemiology would encompass a whole community or population. Therefore, epidemiology refers to the study of determinants and distribution of health related events among human populations and the subsequent application of the study in prevention and control of problems in health (Brandt & Feuerstadt 2011). Kanchanaraksa defines it as a branch in medical science that concerns the incidence, distribution and subsequent control of diseases in human population (2008, p.1). This discipline relies more on quantitative studies to measure diseases from infection to resolution and analysing the occurrence pattern in an individual or groups of people which could alter health (Rothman, Greenland & Lash 2008). Distribution would be determined by place, time and person and by frequency of events of health giving rise to descriptive epidemiology. Analytic epidemiology on the other hand would involve searching for risk factors, response to hypothesis of a study and use of varied epidemiologic methods. Epidemiology has now been extended to cover not only human beings but also populations of any species. Scholars in epidemiology have quoted various conditions that propagate infection of diseases. Carneiro et al. (2005) argue that early weaning among mothers has been a risk factor with regard to infections such as rotavirus gastroenteritis. Climatic conditions have also been known to influence infections with winter being associated with rotavirus gastroenteritis infections. Industrialisation has led to increased pollution which has triggered varied infections among human beings. Environmental changes have caused increase in respiratory diseases and incidences of cancer in young people. Incidence would also increase with the host being more susceptible. An epidemic would result with increase in agent amount, recent agent introduction, emergent entry portals being introduced, increased host exposure and when the mode of transmission is enhanced (Rothman, Greenland & Lash 2008). Transmission could occur in three forms: contact, vehicle or vector transmission. Contact transmission involves direct person-to-person interaction, indirect or through droplet. Direct contact would be through touching, sexual intercourse or kissing. Indirect contact would be through inanimate objects which Brandt & Feuerstadt (2011, p.77) refer to as formites. Droplet transmission arises out of sneezing, coughing or spitting. This should be within one metre from exiting the mouth, otherwise this would be considered as air-borne. Air, food and liquids serve as vehicles through which transmission occurs into the body thus vehicle transmission. This could be airborne, water borne or food borne transmission. Micro organisms have adopted specialised features to enable them enter the nervous system. These could occur through the blood, lymphatic organs, peripheral nerve axons and parenteral and has been referred to as vector transmission (Carneiro et al. 2005). According to Rothman, Greenland and Lash (2008), transmission would depend on the number of susceptible contacts and infectiousness durations. For example, commercial sex workers would most likely contact STDs because of regular frequent contact with varied partners. Transmission could also occur vertically or horizontally from mother to child. Vertical transmission encompasses transmission of agents causing diseases just after or before birth through breast milk or placenta while horizontal transmission encompasses all other possible forms of transmission. To make epidemiological predictions, knowledge on the following would be required: risk of infection and risk of infection transmission for the infected. Rothman, Greenland and Lash (2008) note that susceptibility could be related to transmission, for example in cases of vector borne diseases, but quite distinct in cases such as infections transmitted orally and through faeces. John and Samuel (2000) also indicate that in herd immunity, as the infection causing agents spread in a population, the susceptible proportion would decline. If this trend continues, transmission could completely be halted. Kanchanaraksa (2008, p.8) outlines the steps involved in disease outbreak investigation. The first step involves preparation for field work. This would be followed by establishment of the existence of the outbreak including severity, frequency, spread potential, resource availability and public concern. The diagnosis would then be verified and the cases defined and identified. Data would then be described and oriented according to time, persons and place, referred to as descriptive epidemiology (Woolhouse 2011). A hypothesis be developed and evaluated. This calls for a control group against which the results would be based. Refinement of hypothesis would pave way for the implementation of control and prevention measures. Finally, the findings would be communicated. Whatever model would be used in epidemiology, the basic idea would be to use the past experience or expert opinion to accurately guide the future. Different levels of predictability exist: with no change, the input data, model and parameter values would be applicable even to the emergent epidemic; input data would have factors such as size and location change; value change would involve for instance the introduction of a different strain having different transmission traits; and model change where the original model assumptions would be incorrect when the new model would be considered. B) Immunisation programmes Principles of acquired immunity According to Grady (2004), resistance to disease in humans would ride on innate mechanisms and acquired immunity. Human beings would be protected through biochemical and physical factors. They acquire immunity through two possible mechanisms, namely; active immunity acquired through one’s own immune system after a vaccination or contamination and passive immunity produced by humans or animals and would be injected into humans. Acquired immunity work in a specific way and would supplement the natural or non-specific short or long term resistance mechanisms including macrophages, granulocytes and chemical barriers like lysozymes. Passively acquired immunity would result from acquiring immunity unintentionally from the environment while actively acquired immunity would be a product of intentional acquisition. Vaccines work through interaction of cells and factors that contribute towards immunity acquisition in humans. National Institute of Allergy and Infectious Diseases, NIAID (2012) argue that the immune system exists as a complex network of tissues, cells and molecules dispersed in the body. Each of these plays a distinct role and would interact in an orchestrated and coordinated manner generating specific and timely response to a vaccine or pathogen. Vaccination elicits specific immune response leading to protection of an individual when later exposed to pathogens. Inactivated agent forms would be used to stimulate protective response without the disease being triggered. This capability could be enhanced using adjuvant which attracts extra inflammatory cells, antibodies, T cells and B cells to sites of injury, causing them to release different cytokines. These chemical signals would cause a further stimulation and activation of lymphocytes and macrophages for enhanced protection. The mechanisms and processes involved would be similar for both actively and passively acquired immunity. The unique traits of intracellular pathogens dictate that vaccines elicit vigorous cell-antibody mediated responses. Effective vaccines should stimulate antibodies production before pathogens enter cells and elicit cyto-toxic T cells which destroy cells that harbour pathogens. Unlike other therapeutic procedures, vaccination protects against onset and progression of infectious diseases and would uniquely harness cells, molecules and tissues of human immune system to mediate protection through natural mechanisms which are fundamental to the biology of human beings. Vaccinating a large proportion of people in an area limits spread of infectious diseases. Indirectly, those who would not have been immunised or those whose vaccination becomes unsuccessful would also be protected. This is referred to as the principles of herd immunity (John & Samuel 2000). Diseases transmitted from a person to another would be difficult to maintain in chain where a considerable proportion of the population has been vaccinated. The more the population of those vaccinated, the higher the protective effect of the herd immunity (NIAID 2012). Some diseases have been contained with as little as 40% of the population vaccinated but depending on contagiousness, the herd immunity threshold has been capped at 80% to 90% according to John and Samuel (2000). For herd immunity to be effective the disease agent should be restricted to a particular host species and transmission should be direct from a member to another. Vaccinations have drawn a lot of controversy from development stage through its use. Ethical debates should be based on their good to the community at large as opposed to benefitting an individual according to Grady (2004). Among the major concerns includes the role of government and policy makers in the development, promotion and monitoring of vaccines; identifying and evaluating risks and benefits involved; and appropriate place of immunisation in programs of public health (Schwartz & Caplan 2011). These scholars found mandatory vaccination for select populations to be indispensable in building and maintaining high rates of vaccination in the US. Therefore, they should only be implemented in limited circumstances only. In herd immunity, the concern has been that an individual’s acceptance or declinature to be vaccinated affects the whole community. The contentious issue has been whether to observe the duty to respect individual rights against helping others. There are risks associated with immunisation that have caused the public to shun from vaccination programs. Live attenuated vaccines used to prevent respiratory syncytial virus have been cited to increase infant mortality and cause severe diseases. In 1976, swine influenza vaccination had to be stopped as it was linked to increased Guillain-Barre syndrome. There have been similar claims in African countries where it is argued that massive polio immunisation led to spread of HIV. These claims have resulted to negative perceptions on immunisation. Christians have argued that if God decreed one to die of a disease, preventing it through vaccination would be going against the will of God which is tantamount to sin (WHO 2012). Nonetheless, much success has been achieved in immunisation programs. This could however lead to complacency on the need for high level vaccination in the community. The principles of success should ensure that the gains achieved continue to be promoted and reinforced. 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