Tuesday, January 17, 2012

Research Paper on Diseases

Research Paper on Diseases

1. Description of diseases
1.1. Malaria
Malaria is among the major causes of death in the world and kills over a million people annually. (Kujtan). Although this virus kills less than 1% of those who actually contract it, the high infection rates (over 300,000,000 people contract the disease every year) account for the impressive mortality figures. Malaria “kills more people than any other communicable disease except tuberculosis” ( The deaths primarily occur among young children in Africa, especially those who live in the countryside and have poor access to health care (


Malaria is spread mostly in tropical and sub-tropical areas including Africa, India, the Caribbean and South America, but affects people from other countries travelling to those areas as well. For example, in North America, over a thousand people are diagnosed with this disease annually after trips to the warmer regions (Kujtan). Over 90% of all malaria cases are reported in sub-Saharan Africa. Overall, this disease is found in 101 countries: “45 countries in Africa, 21 in the Americas, 4 in Europe, 14 in the Eastern Mediterranean Region, eight in South East Asia and nine in the Western Pacific Region” ( Currently, the infection has appeared in the regions where it was exterminated years ago, such as Tajikistan, Azerbaijan, and Korea. Although the area affected by the disease has become smaller than 50 years ago, it is still a huge part of the world. Malaria is a major health problem now in over 90 countries with a population of 2,400 million people that represent 40% of the global population ( Malaria risk is increasing as methods of land use are changing due to the development of road construction, mining, logging, and agricultural and irrigation projects. International travel, flows of refugees caused by armed conflicts and global climatic change are also exacerbating the malaria situation around the globe. The particular forms of malaria spreading have become “airport malaria” when the disease is imported by travellers, and "weekend malaria," that affects town residents in Africa getting back to their rural settlements. The United Kingdom recorded 2,364 cases of malaria in 1997 brought to the country by travellers (

The disease is caused by Plasmodia, one-cell creatures that get into human blood after bites of infected anopheline mosquitoes. The parasite inside the body of the human gets into the liver, incubating there. Malaria is more frequently transmitted during a rainy season ( Malaria can also be contracted through blood transfusions or dirty needle use (Kujtan).

Malaria symptoms include “fever, shivering, pain in the joints, headache, muscle aches, tiredness, repeated vomiting, generalised convulsions and coma”, possibly also nausea, vomiting, and diarrhoea (

If malaria is quickly diagnosed, it can be cured, which is why the majority of people who develop malaria survive. Malaria is diagnosed via a malaria smear that is a drop of blood that is examined under a microscope. Malaria has four different forms, three of which are “benign”, meaning that the patient has a fairly good chance of survival, while the fourth one is dangerous as it can lead to death within 48 hours. If the disease is not fully cured, the symptoms can return in a few months.

Malaria surfaces in the regions affected by hurricanes, for example, in the Caribbean. The disease was once common in the southern US but was eradicated later on (Kujtan). Currently the instances of malaria transmission in North America are limited to the cases when infected mosquitoes have come to the continent in travelers’ bags or have bitten local mosquitoes.

The studies of the economic impact of malaria in Africa, the region most affected by this deadly malaise, have been looking into the losses caused by the outlays for treatment, lost productivity due to missed working hours, households’ expenditures on medication and treatment, the days missed by schoolchildren at educational establishments, expenses at public health care offices, and the impact on people’s health. A study by Shepard et al. in 1991 revealed that the economic loss from malaria to the African continent in 1987 amounted to $791 million, constituting 0.6% of the Sub-Saharan Gross Domestic Product (Chapter 6:164). The study by Leighton and Foster in 1993 estimated the production loss inflicted by malaria on the economies of Kenya and Nigeria to be in the ranges of 2-6% of the GDP and 1-5% respectively (Chapter 6:165).

1.2. West Nile virus
West Nile Virus is contracted by people most commonly from mosquitoes or birds (CDC). Other creatures that spread the disease include insects such as sand flies, ceratopogonids, "no-see-ums", ticks, and vertebrates such as dogs, cats and horses. The contraction of the virus by humans is accidental, and the human being cannot be infected by the West Nile Virus as a result of communication with another human. In 80% of the cases the disease will be asymptomatic, but in 20% of the cases humans will develop a serious condition called West Nile fever or West Nile disease (CDC). The symptoms of the West Nile Fever are “fever, headache, tiredness, and body aches, occasionally with a skin rash (on the trunk of the body) and swollen lymph glands” (CDC: Symptoms of West Nile Virus). The contraction of the virus can lead to encephalitis affecting the brain itself, meningitis that affects the lining of the brain and spinal cord, West Nile meningoencephalitis (inflammation of the brain and the membrane surrounding it), and West Nile poliomyelitis (inflammation of the spinal cord) called then West Nile disease, or neuroinvasive disease ( the symptoms of the West Nile disease include “headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis” (CDC). The risk of developing a disease is especially common in people over 50 or those with damaged immunity, such as transplant patients. The incubation period usually lasts from 2 to 15 days, and the disease itself is usually over in a few days, although in some patients the symptoms may persist for weeks.

West Nile fever is typically of short duration and does not leave any lasting health effects. On the other hand, the West Nile disease can evoke “permanent neurological damage” and result in the death of the patient ( The death rate of those infected with West Nile virus is less than 1 person in 1000, as less than 1% of those who contract the virus develop encephalitis, and the rate of fatality among encephalitis patients varies from 3% to 15%.

This dangerous virus first entered the Western Hemisphere and was registered in New York in 1999 (Zohrabian). Since then, the virus spread all over the US and most of the states registered WNV-positive in 2004, except Washington. Some of the Mexican and Canadian provinces bordering on the US were affected as well (US Geological Survey). During the outbreak of the disease in 2002, 4,156 WNV cases were registered in the United States. 2,942 people developed a condition affecting the central nervous system. 284 disease cases led to lethal outcomes (Zohrabian).

A study was conducted aimed at assessing the economic impact of the disease in Louisiana where 329 cases were reported in 2002, including 24 lethal cases. The research took into account “medical costs (inpatient and outpatient); nonmedical costs, such as productivity losses caused by illness and premature death, costs of transportation for a patient to visit a healthcare provider, and childcare expenses; and costs incurred by public health and other government agencies for epidemic control” (Zohrabian). The costs associated with the short-term impact on the epidemic on the economy of the state including the factors mentioned above were found to equal $20.1 million, and the figure is likely to be understated as some of the costs such as expenses associated with outpatient medication and others were not available to the researchers. The scientists extrapolated their findings on the local impact to other regions. Assuming that Louisiana was a representative state, the cost to the nation of the epidemic in the time span between June 2002 and February 2003 was found to be $139.8 million, including $57.5 million in short-term costs of inpatient treatment, $5.6 million for outpatient treatment costs, and non-medical costs of $76.7 million (Zohrabian). The long-term impact can be expected to be even greater as some of the patients were not able to get back to their jobs immediately after the end of the given timeframe and expected to continue with treatment.

1.3. Dengue
Dengue is world’s most common arthropod-generated disease. There exist four serotypes of the dengue virus (DENV), all of which are transmitted by the mosquito Aedes aegypti. If a person has experienced infection with one dengue serotype, the person acquires lifelong immunity to that type, but can fall victim to other serotypes (WHO Fact Sheet).

Currently, over 50 million people around the globe contract dengue every year. On the American continent, the epidemic of the dengue occurred in the 1980s starting with the first outbreak of dengue haemorrhagic fever/ dengue shock syndrome in Cuba.  Now dengue is found in many countries in North and South America. In 2002, 75% of the cases found in the Americas were registered in Brazil (Cruz 2002: 1).

Dengue infection can result in a variety of conditions ranging from a mild ailment (undifferentiated febrile illness (viral syndrome)), to an illness whose symptoms resemble the grippe (dengue fever (DF)) to the most severe condition called dengue haemorrhagic fever (DHF) including dengue shock syndrome (DSS) that can lead to a lethal outcome within 24 hours. The fatality rate for dengue haemorrhagic fever can exceed 20% without proper treatment, but with intensive therapy this figure can be reduced to 1% (WHO).

Undifferentiated fever usually develops in children infected with DENV for the first time and has the same set of symptoms as other virus infections. Sometimes this disorder is accompanied by maculopapular rashes. Dengue fever is accompanied by “headache, myalgias, arthralgias, rashes and leucopenia” (WHO Fact Sheet). Sometimes the disease is accompanies by more severe symptoms such as muscle and joint pain and haemorrhage. Dengue fever usually does not affect the local population in the areas where this disease is endemic.

Dengue haemorrhagic fever occurs with a quick advent of high fever, often accompanied by the liver enlargement. In some cases this acute condition is accompanied by circulatory failure. The fever reaches 40-41 degrees Celsius, along with febrile convulsions and haemorrhagic phenomena. The fever subsides after 2-7 days, after which symptoms usually disappear. If the patient enters dengue shock syndrome, death can follow within 12-24 hours if he/she is not rescued by intensive therapy. DHF usually occurs in people who have already experienced the DENV infection, although sometimes it can be found in people who are contracting DENV for the first time (WHO Fact Sheet).

Dengue was found in only 9 countries before 1970, but since then the disease has been gaining spread and severity. The number of the countries reporting dengue has risen by four times and continues to increase. Every year viruses cause infections in almost 100 tropical countries, leading to 2,000-3,000 deaths, primarily of children. The pandemic of the 20-21st century was caused by the changes in lifestyles that came with “population explosion, urbanization and rapid transportation of large numbers of people” (Pan American Health Foundation). The new conditions in the developing countries where population growth has been especially quick precipitate the spread of the infection creating a more favorable environment for the main DENV transmitter, Aedes aegypti. Quick migration of the developing nations’ population to cities with poor urban infrastructure, inadequate water supply, and heaps of solid waste can lead to high proliferation of Aedes aegypti (WHO). Modern trends of international trade contribute to the transportation of the mosquito’s larvae in the used tires where rainwater accumulates (WHO).

Some estimates claim that de-facto infection rates are even higher as the number of deaths may in fact total 12,000 per year as not all the cases are reported to the WHO (WHO). The pandemic is on the rise on the American continent, in the Eastern Mediterranean, Southeast Asia, and Western Pacific (WHO). In the unprecedented pandemic of dengue fever and dengue haemorrhagic fever in 1998, 1.2 million cases were registered in 56 countries worldwide.

1.4. Plague
Plague can be of three different forms: bubonic plague, septicemic plague, and pneumonic plague differing in their clinical features. The symptoms of bubonic plague are enlarged, tender lymph nodes, fever, chills and prostration. A person develops a blister at the site that was bitten by the flea. Sometimes a patient develops ulcers in places of the lymph nodes, such as groin, armpit, and neck. The patient suffers from extreme exhaustion and delirium.

Septicemic plague is characterized by “fever, chills, prostration, abdominal pain, shock, and bleeding into skin and other organs” (Wrong Diagnosis). Pneumonic plague affecting the lungs causes “fever, chills, cough, difficulty breathing, and rapid shock and death if not treated early” (Wrong Diagnosis).

Bubonic plague offers better chances of survival, but if the disease is left untreated, the bacteria get into the blood and proliferate there. In this way they spread throughout the body leading to a severe condition that often leads to death.

Pneumonic plague occurs when the lungs are infected. This is a serious respiratory illness that may lead to quick death unless the patient is given quick antibiotic therapy.

Plague is caused by bacillus called Yersinia pestis transmitted by fleas. Humans most often get fleas from rats, which was why the disease was more common in the Middle Ages when towns and villages were teeming with rats. The bacillus is transmitted via “direct contact with infected tissues or fluids from handling sick or dead animals” or from “respiratory droplets from cats and humans with pneumonic plague” (Wrong Diagnosis). Fatality rate reaches 50-90% if the disease is not treated; 15% in case of proper diagnosis and treatment.  About 14% of all plague cases in the United States result in the death of the patient.

Throughout the history of mankind plague has taken almost 200 million human lives. Starting with the first outbreak of bubonic plague in Europe during the 6th Century, the disease became the scourge of the mediaeval world. Plague comes from the Gobi Desert and achieved a pandemic reach in the 14th century. In the Middle Ages plague killed nearly one-third of the population. The disease quickly spread through Asia along the trade routes. Although this terrible death is typically associated with Europe, it was as ruinous in other parts of the world. Even countries situated at a significant distance from Europe such as China were affected. The epidemic of plague in China in 1328 reduced the country’s population to 90 million from 125 million. With the advent of European shipping, the terrible disease spread to the areas such as the Crimea and Egypt. The size of the pandemic had a devastating effect on the size of the population of the mediaeval world, as whole areas became depopulated as people were fleeing from the areas where the disease was found. A special place in the history of mankind takes the Black Death of 1665 that almost halved the population of the British capital (Black Death).

The last outbreak of plague happened in the US in Los Angeles in 1924-25 (CDC).Now the WHO reports about 1,000- 3,000 cases per year (CDC).In North America plague occurs in animals and fleas in the areas located from the Pacific Coast to the Great Plains, and from south-western Canada to Mexico. The spread of the plague in the US is limited to two great areas. One is northern New Mexico, northern Arizona, and southern Colorado, and the other includes California, southern Oregon, and far western Nevada. Plague is found in a number of countries in Africa, Asia, and South America (CDC). The people who are in the risk group for contracting plague include those who often come in contact with rodents, for example, foresters, veterinarians, etc. Hikers or campers entering areas infected with plague can also catch the infection. In the United States plague is often transmitted by animals other than rats such as squirrels, prairie dogs, and other burrowing rodents.

2. Comparison
The four diseases described above all take a heavy toll on the human health, and when it comes to an individual illness, they all have an adverse impact on the human being. But if one thinks in global terms, the seriousness of the damage is not the same.

2.1. Economic perspective
From the global historical perspective, plague has been most detrimental to the progress and well-being of human society. We could claim that is affected the history of mankind reducing the size of population by a third in the Middle Age. Plague disrupted ties between different areas as authorities were seeking to protect the people by sealing off towns and villages affected by the plague.

However, now plague has fortunately lost the significance of a history-shaping factor. Although it is still found in Asia, Latin America and Africa, it can hardly be called the deadliest disease of the 21st century. 1,000 – 3,000 cases reported by the WHO annually with approximately 15% of mortality among those who receive proper treatment do not present a serious danger to the world’s population.

Among infectious diseases, plague has yielded its horrific first place as human killer to malaria that is responsible for 300, 000, 000 infections per year. Even with a mortality rate under 1%, with the number of infections, this disease posts a serious threat to the population of 90 countries where the disease is found.

Perhaps the most serious implication of malaria is the economic loss it inflicts on the Sub-Saharan region in Africa. The annual economic loss, as indicated in the section on malaria, amounted to $791 million, although the real numbers were estimated to be much higher. In comparison, the economic damage wrought by the West Nile virus in the US was assessed to amount to roughly $140 million. The comparison of the two numbers needs to provide for the striking difference in the size of the Gross Domestic Product in the US and Sub-Saharan Africa. The United States can ward off the impact of a similar economic loss with much greater resilience than the countries in the less affluent world.

2.2. Current situation
From the point of view of the dynamics of the disease spread, dengue is one infection that has been on the rise of late. Originally confined to only 9 nations, it has now expanded to over 100 countries worldwide, claiming at least 2,000 – 3,000 lives a year or 12,000 by broad estimates.

On the other hand, other infectious diseases have shrunk in the past few centuries. Plague that was a global factor in the Middle Age is now an important social phenomenon in a handful of developing nations and has been practically eradicated in developed countries. The area affected by malaria has also shrunk in the past 50 years, although a severe battle with this disease still lies ahead as it began to re-emerge in the Asian regions where is had been eradicated, such as Korea and Central Asian republics.

In the North America, only 1 to 40 cases of plague are found per year. This compares to about 4,000 cases of West Nile Virus registered in 2002 in the US. The virus that entered the American continent in 1999, quickly spread to the majority of the states, and is now found in some Mexican and Canadian provinces. This proves that this infection is probably the greatest challenge of the four for North America. Malaria and dengue fever are also found in only scattered cases, malaria mainly imported by travellers returning from tropical countries.

2.3. Clinical perspective
From the clinical perspective, all the four diseases can progress in a relatively mild form, while in a minority of cases a more serious form can develop that has significantly higher mortality rates. West Nile virus can lead to encephalitis, meningitis, meningoencephalitis, or poliomyelitis. Malaria has one form that may cause death within 48 hours as opposed to the other three benign forms. Plague mortality is higher if the patient develops a seroseptic or a pneumonic form, and dengue can lead to death if a patient develops dengue hemorrhagic fever leading to dengue shock syndrome. Thus, lighter forms of the disease caused by the same virus or bacillus have much lower mortality rates. For example, only less than 1% of those infected with West Nile Virus die, but for those who develop West Nile virus encephalitis, the rate is 3 to 15%.

Proper treatment is also important. Among those who contract plague and do not get quick therapy, the fatality rate is 50-90%, while among patients who have access to treatment the rate shrinks to 15%.
While dengue, West Nile Virus and plague are typically cured completely unless the infected person dies, malaria symptoms can recur in a few months, making this disease a more debilitating experience.

2.4. Epidemiology
West Nile Virus is transmitted by both birds and mosquitoes, while dengue and malaria infections are spread by mosquitoes. This means that the infection rates for these diseases can be reduced by trying to disrupt the environments favorable for the mosquito proliferation, such as damp areas.
The plague, in contrast, is transmitted by fleas that bite humans, and fleas reside in the rats’ fur. That is why the plague was conquered when the developed nations freed their towns and settlements from rodents and found ways to get rid of the parasites.

Taking into consideration all of the comparisons outlined above, we will conclude that the most serious disease from the global perspective is malaria. First, it affects the poorest regions of the world, eating at their already poor economic strength. Second, the overall size of the economic damage is significant. Third, malaria is a disease with recurring symptoms unless cured completely.

From the personal perspective, plague can be considered the deadliest disease. While any of the above-mentioned disorders leave a debilitating effect on the body, plague has the highest mortality rates that are above those for any other infection. Besides, it affects the immunity system, which is extremely harmful.

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