Medical+Geography+and+Epidemiology

__**1. What is Medical Geography?** __ __ **2. Why food matters: Food Insecurity, Hunger, & Malnutrition. ** __ __** 3. How are diseases differentiated? ** __ __** 4. What is the point of Epidemiologic Transition and how does it explain disease? ** __ __** 5. What are disease causing agents and what are their roles in disease diffusion? How do vectors and reservoirs play into this diffusion? ** __ __** 6. Why are death rates different between places? ** __ __** 7. What roles do physical and social environment, mobility and migration, and human behavior play in the diffusion of disease? ** __

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Medical geography is a new hybrid of research between geography and medicine involving the geographic aspects of medicine and healthcare. The goal of this research is to improve the understanding of factors which influence the health of populations. For emample, In the early 20th century a couple of dentists in Colorado noticed that children living in areas with high levels of naturally-occurring fluoride in groundwater had fewer [|dental caries]. Their discovery of the value of fluoride came from the application of medical geography (which, since this is dental geography, might be better called health geography). http://www.medterms.com/script/main/art.asp?articlekey=18879

This field of geography ** did not gain prominence until the mid-1800s though when cholera gripped London. As more and more people became ill, they believed they were becoming infected by vapors escaping the ground. [|John Snow], a doctor in London, believed that if he could isolate the source of the toxins infecting the population they and cholera could be contained. ** ** http://geography.about.com/od/culturalgeography/a/medicalgeograph.htm **


 * Although at the time doctors believed that the cause of the disease was bad air, “Snow held a radically different view. Snow, who was also well known as the founder of anesthesiology, suspected that the real culprit was drinking water contaminated by fecal waste.” (Founders of Modern Epidemologhy handout p. 6). **

What is Medical Geography?: Medical Geography consists of many different aspects, including:
 * Diffusion of disease (through bodily fluids, airborne and food borne illnesses, and migration)
 * Sanitation (the number one way to stop influenza is to wash your hands)
 * Distribution and diffusion of medical services (relating to insurance and access)
 * Epidemiology - The study of the causes, distribution, and control of disease in populations
 * If a disease is **endemic**, it is in its early stages and always there
 * If a disease is **epidemic**, there are a few outbreaks and the situation gets more serious
 * If a disease is **pandemic**, this is a serious situation and it means that there is a global outbreak

Why //**ACCESS**// to medical care is so critical... media type="custom" key="7681737" width="45" height="45" align="left"


 * FOR FOOD, CLARIFY EXACTLY WHY IT IS CRITICAL TO AN UNDERSTANDING OF MEDICAL GEOGRAPHY**


 * __Why food matters: Food Insecurity, Hunger, & Malnutrition__**

=
Food Security is that availability of food and the ability to obtain it. When you cannot obtain food or nutrients, Food Insecurity, Hunger and Malnutrition are usually the results. ======
 * 1) Food is important because it provides energy and nutrients needed for growth, activity, reproduction and body maintenance. Carbohydrates, fats, proteins, minerals, vitamins and water are all essential to lead a healthy, active life. If one of these things is compromised, it can lead to deficiencies or malnutrition.


 * Food Insecurity- A household has limited or uncertain access to safe, nutritious food for an active and healthy life. These households may have irregular food intake or poor quality meals. There is a possible need to resort to extreme methods in order to obtain basic food needs.
 * Hunger- A more severe level of food insecurity. Results from insufficient or irregular food intakes resulting in periods of hunger (uneasy or painful sensation caused by lack of food).
 * <span style="font-family: 'Arial','sans-serif';">Malnutrition- An imbalance between the body's needs and the intake of nutrients, which can lead to syndromes of deficiency, dependency, toxicity or obesity. Malnutrition includes under nutrition, in which nutrients are under supplied, and over nutrition, in which nutrients are oversupplied.
 * <span style="font-family: 'Arial','sans-serif';">Some examples of deficiency diseases include: Vitamin A deficiency (blindness), Vitamin C deficiency (scurvy), Vitamin D deficiency (rickets), and Iron deficiency (anemia)
 * <span style="font-family: 'Arial','sans-serif';">[|Food consumption per capita]
 * On Earth, the food supply differs depending on location. According to the map above, food consumption in North America and Europe is significantly higher than the rest of the world.
 * In areas with higher income, people tend to eat more meat and dairy product, while in countries with low income, the food supplies are mainly made up of cereals.
 * There are over 500,000 edible plants on earth but 15 make up 90% of those consumed.


 * There is a direct link between poverty and malnutrition. If a person is in a state of poverty, then their immune system may be compromised due to malnutrition. With less food, a person has lower energy levels and a decreased ability to work, which leads back to a state of poverty. Eventually, the cycle will lead to an increased death rate and a lower life expectancy.
 * This cycle is all too common throughout the world and the main question is how to break the cycle.
 * Some believe that by getting the people out of poverty, the cycle can be broken however others believe that by supplying the affected people with food, the chain can be broken.

__**How are diseases differentiated?**__

Diseases can be separated into four categories: infectious, chronic, genetic, and environmental.


 * Infectious (communicable) diseases**- Infectious diseases are caused when a virus, bacteria, fungi, prions, or protists (see below for description) enters the body. Once the germ is in the body it grows and multiplies. Infectious diseases can (but are not always) transferred be transferred from person to person through vectors. Examples of infectious diseases are chicken pox, malaria, and bird flu, other examples can be found at http://www.medicinenet.com/infectious_disease/focus.htm.


 * Chronic diseases- ** A chronic disease is defined as a disease that lasts more than three months. Chronic diseases cannot be by vaccines or cured by medicine. Behavior's such as use of tobacco, lack of physical activity, and bad eating habits lead to chronic diseases. Chronic diseases increase with age, 85% of people age 65 and older have a chronic disease. Chronic diseases are the leading cause of death and disability in the United States, accounting for 1.7 million (70%) of deaths per year. Some chronic diseases, such as arthritis, are not life threating, while others, such as cancer, can be fatal. (referenced from http://www.cdc.gov/nccdphp/ and http://www.medterms.com/script/main/art.asp?articlekey=33490)

For most genetic diseases the disease can be traced to cretin genes, but there are some diseases such as asthma, diabetes, and some cancers that cannot traced back to a gene that carries that disease. (referenced from http://www.medicinenet.com/genetic_disease/article.htm )
 * Genetic diseases- ** A genetic disease is caused by abnormalities in a person’s genome(set of genetic information). Most genetic diseases are caused by mutations in one’s genes: four types of mutations are Single gene inheritance, Multifactorial inheritance, Chromosome abnormalities, Mitochondrial inheritance.
 * __Single gene inheritance__- This is caused by a change or mutation in the DNA sequence of a single gene. This kind of mutation occurs in about 1 out of 200 births. There are over 6,000 kinds of single gene inheritance diseases, including cystic fibrosis, marfan syndrome, and huntington’s disease.
 * __Mutifactorial inheritance__- This is caused by caused by environmental factors and mutations in more than one gene. Examples of mutifactorial inheritance diseases are Alzheimer’s disease, arthritis, and cancer.
 * __Chromosome abnormalities__- Chromosomes are located in the nucleus of cells and carry genetic information through the body. Because Chromosomes carry information through the whole body, abnormalities sin them can lead to diseases. Examples of Chromosome abnormalities are down syndrome and cat cry syndrome. http://www.medicinenet.com/genetic_disease/article.htm
 * __Mitrochondrial inheritance__- This is a genetic disease caused by mutation in the nonchromosomal DNA of mitochondria. Examples of mitochondrial inheritance diseases are Leber's hereditary optic atrophy and cretin types of epilepsy.

**Environmental diseases (TOXISM)-** Diseases caused exposure to environmental toxins. Some diseases will occur with long term exposure (such as radon), others will come from just a little exposure to the toxin ( such as lead poisoning). Environmental toxins can be air born, in water, in food and other surfaces. (referenced from http://www.cdc.gov/nceh/ehs/Topics/default.htm )

__<span style="color: black; font-family: 'Arial','sans-serif';">**<span style="font-family: 'Arial','sans-serif';">What is the point of Epidemiological Transition and how does it explain disease? ** __

According to the Centers for Disease Control, epidemiology is a “branch of medical science that deals with the incident, distribution, and control of disease in a population.” Epidemiological Transition is the “secular, or long-term, change in disease and mortality patterns.” The theory of this population shift was adapted from the early terminology of the demographic transition. The transition is split up into four different periods, each one varying with the social and economic context of a given population. The four periods are as follows: (http://www.cdc.gov/malaria/distribution_epi/epidemiology.htm)
 * What Is Epidemiology?**

Four Stages of Epidemiological Transition

( http://www.dcp2.org/slides/310/preview )
 * 1st Stage: Pestilence and Famine**-
 * This stage prevailed throughout most of human history. It's characterized by extremely high death rates that vacillated between peaks and trouts in response to epidemics, famines, and war.
 * Birth rates were high and fairly stable
 * Death rates were equally high and kept population growth minimal.
 * 2nd Stage: Receding pandemics**-
 * This era (Late 19th century in Europe and America) was a combination of factors including better sanitation, nutrition, and vaccines and medical advances, allowing some human control over the previous incestious and parasitic disease.
 * This is when rapid population growth, a new phase of demigraphic history of humans, was introduced.
 * 3rd Stage: Degenerative and Human-created disease**-
 * This stage was driven by "socially determined" factors in developed nations like lifestyle changes and better public health as well as medical technology in the developing world.
 * Chronic disorders associated with aging (such as cancer and cardiovascular diseases) became the leading cause of death while infectious and parasitic diseases receded.
 * Death rates fell (10 deaths per 1,000 population) in developed areas
 * Birth age rose above 70 years because of declines in death rates among those surviving to middle and older ages
 * 4th Stage: Delayed Degenerative diseases-**
 * In the latter part of the 20th century, death rates from these chronic degenerative diseases began to decline rapidly.
 * For example, heart disease decline more than 30 percent between 1968 and 1982, concentrated among people at middle and older ages.
 * Presence of major degenerative causes of death but life expectancy is lengthened due to medical advances (and the continuation of standards of living) permitting individuals with diseases such as cancer and cardiovascular disease to survive to older age.

The theory never states explicitly that infectious and parasitic diseases would be eliminated. It suggested that the causes of death predominant throughout most of human history would be replaced by chronic degenerative disease associated with survival into older ages. Socioeconomic development, sanitation, public health and advances in clinical medicine affect the overall transition. Socioeconomic factors initiated the epidemiological transition in the United States and western European countries— where the transition first began. So-called “social pathologies” such as homicide, cirrhosis of the liver, suicide, and HIV/AIDS were among the leading killers of Americans in the 1980s and 1990s. Tuberculosis is undergoing a resurgence in the United States, as are several other communicable diseases associated with poverty and unhealthy lifestyles. More information can be found at http://www.who.int/topics/epidemiology/en/

Types of Epidemiological Transition:
 * 1. Epidemic**- The breakout of a disease of temporary high prevalence.
 * In the late 1840's, a cholera epidemic was prevalent in London. The disease, which affects victims with violent diarrhea and vomiting, can potentially be fatal. Outbreaks of the disease in London were common since the 1600's however, the epidemic of this disease was by far recorded in history. John Snow, well known as the founder of anesthesiology, suspected the outbreak was due to something else besides the suggested "bad air". He discovered the cholera epidemic was due to drinking water contaminated by fecal waste and had the source shut down to ultimately stop the outbreak. Due to the lack of intelligence on the subject as well as medical advancements and clean living, the disease had been around for almost 300 years.
 * 2. Endemic**- When a disease is always present in a prone area and outbreaks occur numerously due to irritation and reintroduction.
 * In Africa, there are numerous countries where malaria is always present and infects people due to reintroduction of the disease. Each year, 350-500 million cases of malaria occur worldwide, and of those, over one million people die, most of them young children in undeveloped African countries. Things as simple as bednets, insecticides, and antimalarial drugs are effective in fighting and ultimately eradicating the disease. However, for these undeveloped countries, that is wishful thinking. The money and resources are not available to inform and prevent the continuation of the disease in Africa. [[image:Picture_3.png width="237" height="186"]]For more information on endemic malaria, visit http://www.cdc.gov/malaria/index.htm
 * 3. Pandemic**- The occurrence of a disease over a much wider geographic area, essentially globally spread.
 * Each year, there is the concern for pandemic occurrence of a new influenza virus. The virus (Avian, or bird flu) emerges for which people have little or no immunity, and for which there is no vaccine. The disease spreads easily person-to-person, causes serious illness, and can sweep across the country and around the world in very short time. Because the disease is so easily spread and continues to evolve into new forms, it is very easy for it so spread globally unless very strict measures are taken. [[image:Picture_4.png width="298" height="204"]] For more information on the flu pandemic, visit http://www.pandemicflu.gov

__**What are disease causing agents and what are their roles in disease diffusion? How do vectors and reservoirs play into this diffusion?**__ Disease causing agents are viruses, bacteria, fungi, prions, and protists
 * __Virus__- A virus can only live outside a body for a limited period of time, but once it enters the body it reproduces. A virus can be lethal to a single-celled organism. In humans viruses can be range from being inconsequential (warts) to deadly (HIV/AIDS, dengue fever, hepatitis B). 12-20% of types of cancers are from viruses (liver and cervical). When a body is infected with a virus, it produces antibodies to fight it. People can be given vaccinations to protect against viruses.
 * __Bacteria__- Bacteria are the most abundant living thing on earth. There are two kinds of bacteria: archaebacteria, found in extreme environments (hot sea floor vents, and eubacteria, found in soil, water, and bodies of animals. Bacteria are attracted to animals because of the moisture and food which are crucial to their survival. Millions of bacteria live in our body to help up fight against fungi and harmful bacteria. Bacteria that is helpful in one part of our body can be harmful to other parts of the body. Most bad bacteria are found outside the body. They can be transmitted through the air (tuberculosis), open wounds (clostridium tetani), or through food (pathogenic E. coli). Some deadly types of bacteria cause acute lower respiratory infections, tuberculosis, diarrheal diseases, whooping cough, and tetanus. Other types of bacteria can be treated with medicine.
 * __Fungi__- Fungi are yeasts, molds, smuts, mushrooms, and mildews. Some fungi live dead cells in our hair, nails and feet. Most fungi, however, lives in soil. Humans and animals protect themselves from fungi with naturally occurring substances in our skin, sweat, blood and saliva. Among the few bacteria's that we cannot fight off are yeast infections, athlete's foot and ringworm. Plants are much more susceptible to fungi than animals. Fungal infections can be treated with medicine.
 * __Prions__- Prions are abnormal proteins found in the brain of healthy birds and mammals. Once a prion appears it takes over nearby normal proteins. Over a period of time enough proteins get taken over and cause holes to form in the brain. All diseases caused by prions are fatal. Creutzfeldt-Jakob disease is a prion disease that is found in humans is thought to be transmitted through brain surgery or organ transplants. Kuru is a prion disease that was transmitted in New Guinean tribe through a ritual where people would eat the brain of the dead.
 * __Protists (protozoa)__- Protists are single celled organisms that are on average a thousand times larger than bacteria. They are found in soil, oceans and freshwater. They prey on smaller microbes. Naegleria fowleria is a protists that lives in lakes and streams in North America that causes a life threatening brain infection if it enters the nose of a human. Most infections caused by protists are not serious; many people in the United States have been infected with the protists infection toxoplasma without even knowing. Other types of protists are very serious, damaging the blood, respiratory and gastrointestinal systems of their hosts. (referenced from [|http://findarticles.com/p/articles/mi_m1134/is_/ai_53682807)//]

//A vector is something does not cause a disease itself but carries disease-causing agents from one host to another host. The disease carrying agent usually does not stay on the vector for a long time. Vectors can be put into one of two categories: live vectors and mechanical vectors.//
 * //A live vector is something that is living that carries disease-causing agents to another host. Live vectors include humans, animals, and bugs. Examples of diseases carried by live vectors are dogs carrying rabies or misquotes carrying malaria. http://www.enotes.com/public-health-encyclopedia/vector-borne-diseases//
 * //A mechanical vector is a nonliving vector. Mechanical vectors include water, air, food, and surfaces. Examples of diseases carried by mechanical vectors are food carrying salmonella and a surface of a door passing on the cold after an infected person touches it.//

//A reservoir is a long term host for a disease causing agent. Humans, animals, and nonliving things (such as soil) can all be reservoirs. Examples of reservoirs are rodents carrying the plague and soil carrying fungal and bacterial diseases such as Clostridium tetani (the bacteria that causes tetanus) http://science.education.nih.gov/supplements/nih1/diseases/guide/understanding1.htm//

//Some times the reservoir is the vector. For example humans are reservoirs for the HIV/AIDS disease. Humans serve as a place for the disease to live and develop and they also carry the disease to one another through direct contact with another person’s semen or blood.//

//The transfer of disease can be stopped if it is cutoff at ether the vector or reservoir. An example of this is Guinea-Worm disease. This may be the first parasitic disease to be eradicated. The vector of this disease is water that is contaminated with worm larvae. The reservoir of this disease is humans. To eradicate this disease all that needs to be done is stop the spread of the disease through water by making the water in infected areas clean. To do this water just needs to be cleaned with chemical treatment or filtered. This disease can be cut off at the reservoir by just stopping people who are infected with Guinea Worm from touching the water and contaminating it.//

//__**Why are death rates different between places?**__// //Where a person lives has a great influence on the death rates. In places that are more developed, the access to food or medical treatment can decide the death rates of an area.//
 * //In less developed ares of the world, there is less access to food (poverty issue, supply issue, seasonal issue). This lack of food can cause deficiencies and malnutrition, which, in turn can cause an inability to work and generate income. This cycle often leads to higher death rates for children and adults.//
 * //In more rural or less developed areas, it is much harder to locate and pay for medical help. Diseases that would easily be combated in places with good medical attention end up becoming fatal because of the lack of medical care.//
 * //In areas where medical attention is easier to obtain and pay for, the death rates are generally much higher.//


 * //The availability of birth control can also determine the death rates. If birth control is not available and no methods are practiced, then people are likely to have more children than they cannot take care of. If parents do not have the means to support many children, then the children may be abondoned, which may cause higher death rates.//


 * //Natural disasters can also affect the death rates. In places with a high susceptibility to natural disasters such as earthquake, tsunamis, hurricanes, etc, the death rates can rapidly increase do to a disaster.//
 * //In 2008 for example, China suffered the Sichuan earthquake which caused over 69,000 deaths. Such a disaster can rapidly increase the death rate in an area.//


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