The Spread Of Infectious Diseases Biology Essay

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Through the last 40 years, concern about the spread of infectious disease has progressed due to the public becoming more concerned about infectious diseases major public health threats. Despite the fact that everything these days is hygienic, hypoallergenic, sterilized, and individually wrapped for your protection, over 30 infectious diseases have cropped up over the last twenty-five years (Patz & Confalonieri, 2004). Even with all these precautions, Infectious diseases have become the leading cause of death in the world and the third in the United States.

Mainly as a result of advancements in medical technology, people are living for a longer time than they ever used to. Even in undeveloped countries the population density has become more intense. Third world countries do not have sufficient sewage systems, pure drinking water, ample housing, or proper medical facilities to handle the rising population. Because of the increasing population, people are packed into congested "megacities," many of which are in humid regions where the environment is ideal for infectious diseases to flourish in (Hay et al. 2005).

Today, in the 21st century, there are over 24 megacities in the world, the majority of them in under developed nations. It is predicted that before the year 2010, half of the world's inhabitants will be residing in congested urban locations (Hay et al. 2005).

The existing economic situation is surely causing numerous rural people to relocate to cities to attain work. Various contagious illnesses that were formerly localized in rural areas are now capable of reaching larger populations by way of rural urbanization. The number of people that dwell in poverty inside large metropolitan areas has grown at an alarming rate. Urban impoverished areas are breeding grounds for diseases comparable to tuberculosis (Hay et al. 2005).

Data compilations, completed in 1990, estimated that there were, "20 million refugees and 30 million displaced people in the world." (Patz & Confaloniere, 2004) Entire population movements were largely due to political, economic or catastrophic events such as flooding, earthquakes and drought are crucial elements in disease development. Such crises lead to temporary living arrangements, such as refugee camps and short-term shelters, which become the perfect environment for the spread of infections. Short-term living spaces frequently share similarities with impoverished city areas. Some of those similarities are; overcrowding, inadequate sanitation, restricted access to medical attention, lack of uncontaminated water and food, displacement, and ineffective barriers for disease-carrying agents. "An example is the movement of 500,000 - 800,000 Rwandan refugees into Zaire in 1994. Almost 50,000 refugees died during the first month from cholera." (Patz & Confaloniere, 2004)

Importing and Exporting of goods

We dine on foods from the world's gardens, except not all imported foods are healthy. Raspberries from Guatemala made a great many Americans sick on account of a parasite known as Cyclosporine, which was in the water that was used to spray and water the raspberries. Potential disease-ridden bugs and tainted foods, vegetation, and other goods cross U.S. borders on daily basis. Ever since the 1980's, the quantity of imported food to the U.S. has doubled. Increases in food imports have endangered the nation's food protection procedure. Despite the fact that we depend on the FDA, USDA and additional government organizations to safeguard our food supply, the number of inspections have reduced by 50% of what they had been a few years back (Garrett, 1996).

Due to the world's countries steadily become more entwined, inter-reliant, and extremely competitive, will the other nations of the world adjust their values to become more akin to those of the U.S. or will the U.S., regardless of elevated principles, turn out to be more susceptible to the rest of the world's germs? (Garrett, 1996)

Sexual Promiscuity and Drug Use

The most recent epidemic on a worldwide scale is HIV/Aids. HIV/Aids appeared in 1979 but it was until the mid 1980s that the disease was given a name. Thirty years later there is still no cure for this disease. HIV/Aids are spread through body fluids with the main ways of becoming effected are through sexual contact and intravenous drug use. In 1997 it was estimated by UNAIDS (United Nations' special program on the AIDS epidemic, that over 16,000 people worldwide were being infected with the HIV virus every day. This epidemic has shown the world that we are continually defending ourselves from an army of microscopic organisms that can emerge or mutate at any time (Eberstadt, 2002).

Intravenous drug use continues to spread the disease far beyond those who inject drugs. Anyone who has sex with an intravenous drug user is at great risk of contracting the disease. Then to make matters worse, children born to HIV infected mothers may also become infected. Since the beginning of the HIV/Aids, intravenous drug use has either directly or indirectly accounted for over 36% of all Aids cases in the U.S. Racial and ethnic minority people in the U.S. are at the greatest risk. It is not only intravenous drug users that are at risk because studies have shown that crack smokers are three times more likely to contract Aids than those who do not smoke crack. Sixty-one percent of all women infected with the HIV virus had contracted it through sexual contact (Eberstadt, 2002).

It is predicted that in the 21st century, the group with the highest risk will be children under the age of 15. In 1997, over half a million children, worldwide, under 15 years old had contracted HIV through birth by infected mothers, sexual contact, and drug use. HIV/Aids is the second leading cause of death for Americans between the ages of 25 and 44. HIV/Aids is the leading cause of death for African American men and women between 25 and 44 years of age. Over half of the reported Aids cases in 1997 were among young homosexual men and 49% of infected women were infected heterosexually (Eberstadt, 2002).

"The HIV/Aids epidemic has also been the cause of another epidemic; Millions of children are being orphaned by HIV/Aids infected parents," quoted by Eberstadt, (2002).

Changes in climate due to Global Warming

Numerous transmittable diseases are extremely receptive to climatic shifts, mainly in temperature, surface water, and moisture. It is evident that climatic shifts are taking place as a result of increased emissions of green house gases. The main causes of climatic shifts are caused by human influences. The typical global surface temperature since AD 1000 began to increase around 1975. From 1975 to 2001, the world's typical surface temperature has increased by .4 degrees Celsius. It is estimated that over the next century, the typical surface temperature will increase 2-3 degrees Celsius (IPCC 2001). According to Karl and Trenberth (2003), "This change in temperature will soon exceed the bounds of natural variability."

The frequency and geographical span of selected plant and animal infectious diseases has apparently altered, to some extent in reaction to climate shifts over recent years. Many infectious diseases are greatly influenced by the altering of local, regional, and global ecosystems that is being done by humans. In tropical regions, dams that were created by humans to store water for irrigation and hydroelectric power have made it possible for water borne diseases to expand in populated areas where they were previously nonexistent. (Harvell et al. 2002).

Human transferable diseases are attributed to an intricate range of conditions making it hard to know precisely what the effects are as a result of climate variation alone. Even so, some data exists regarding an influence of recent climate change on Cholera in Bangladesh, tick-borne Encephalitis in Sweden, and Malaria in regions of eastern Africa (Lindgren & Gustafson, 2001).

There has been extensive research done to establish how human diseases such as malaria

and dengue fever will react to the scope of worldwide climate shifts that are projected to take place over the next century. A great deal more research needs to be completed to conclude how climatic variations will effect microbial mutation and how the recent increase in severe weather events and natural disasters will affect the dispersion of communicable diseases (Kuno, 1995).

Dengue fever is affected by urbanization, travel, trade, and weather conditions. Dengue is by far the most notable vector-borne viral disease of humans. This disease is extremely likely to become affected by worldwide climate alteration. Approx. 80 million cases of Dengue fever are reported each year, of which 20,000 die. Dengue is primarily a tropical disease and has expanded in recent decades to nations with moderate climates. The increase in the number of cases is also attributed to an increase in human mobility via air travel (Monath, 1994).

The Dengue virus breeds in stagnate water locations that are commonly found in the urban environment. This virus strain has accomplished extraordinary evolutionary adjustment to coexist with humans, having originated in the tropical forests of Africa. It has been determined by scientific research, that Dengue is one of the main communicable diseases most expected to be affected by international climate shifts all the way through the 21st century and farther into the future (Monath, 1994).

Many infectious diseases are greatly influenced by the altering of local, regional, and global ecosystems that is being done by humans. In tropical regions, dams that were created by humans to store water for irrigation and hydroelectric power have made it possible for water borne diseases to expand in populated areas where they were previously nonexistent (Kuno, 1995).


The research for this article is qualitative in nature. Qualitative research is a method of used by many academic subjects, such as; social sciences and marketing research. Qualitative researchers have a goal of learning about human behavior (e.g. why and how people do what they do). This types of research focuses on researching specific items of a topic instead of the whole topic and all of its variables.

The research conducted for this paper was focused on six human influenced factors that may or may not be the cause of increased spreading of infectious diseases. A small sampling of specific infectious diseases is discussed in relation to the factors that were researched.

Data Collection Method

The grounded theory data collection method was used for this paper. Grounded theory is used to form a theory or to prove or disprove a current theory from the data retrieved during the process of conducting research.

Analysis of data: Interpretive techniques

The most common analysis of qualitative data is observer impression. That is, expert or bystander observers examine the existing documented data, interpret it via forming an impression and report their impression in a structured and sometimes quantitative form.


The research for this paper has determined that not all infectious diseases have been positively linked to modern day factors. Research in this field is in progress. In order for scientists to determine the factors causing the spread or mutation of a disease, they must first determine the cause of each factor. For example: it has been only recently, that the main cause of climate changes was human influence, had been discovered.


Research on all six factors was conducted by reading and compiling recorded data on factors and the diseases. It was determined that several very serious infectious diseases can be linked to one or more the researched factors. In the last 40 years over thirty new, renewed, or mutated diseases have plagued the world. It was also discovered that all of the factors were influenced by humans. It is my opinion that there is only one main factor that causes the spread of infectious disease, and that factor is humans.


Many of the past diseases that cause worldwide pandemics are still alive and mutating today. One of the biggest threats for the 21st century is the influenza virus. The flu virus constantly mutates and becomes immune to vaccines very quickly. The most recent deadly strain is H1N1 (Nipah virus) also known as the swine flu, and also recently the bird flu (Fong, 2008).

According the St. Johns Providence Health System, "In the first 10 years of this century, the Institute of Medicine (IOM) have noticed a disturbing trend. The number of people diagnosed with diseases such as West Nile, Monkey Pox, and Hantavirus has risen greatly. Diseases that had once been nearly wiped out, such as measles, mumps, pertussis, and malaria, have reappeared. And to top it all off, the spread of sexually transmitted diseases like tuberculosis and Aids appear to be accelerating again."

St. Johns Providence Health System feels that the reason for the escalation is the way humans live. A few of those reasons are: (2010)

Weakened immune systems caused by genetics, other diseases, and malnutrition.

Clearing forests and wetlands increases human's exposure to rats.

Giving antibiotics to farm animals.

The increase in worldwide natural disasters.

War and biological weapons.

Author's note: It will certainly take global efforts to control the spread of infectious disease. It seems that humans have been messing with Mother Nature and she is not very happy about it.