Introduction

To understand emerging and reemerging diseases, you must understand the interconnectedness between human health and the environment and have a grasp on epidemiology.

Human Health

Epidemiology, the study of determinates and distribution of disease in populations, is essential in protecting public health and controlling health problems. Before moving into the specifics of epidemiology, you need to understand some of the basics of human anatomy and physiology; specifically, how the immune system protects us from disease.

Your body’s first line of defense against a foreign invader is keeping the invader out. The skin is part of that defense, as it creates a barrier over most of the body. This defense continues with the mucous membranes lining your nasal pathway, and the hairs help catch particles and keep them from entering your lungs. Tears and saliva both contain lysozymes, which can break down foreign invaders. Bleeding from an open wound helps to rinse away dirt and other particles, and clotting helps keep anything from entering the body through that wound. Your body contains many different types of white blood cells that can fight off a variety of pathogens.

If an invader gets past the first line of the defense, the body’s second line of defense is the immune system. We can acquire natural immunity in two different ways: naturally acquired active immunity occurs when we are exposed to a disease-causing agent (for example, getting chicken pox as a child), and naturally acquired passive immunity occurs when antibodies are received through the placenta or breast milk. We can also attain immunity through vaccinations; this is called artificially acquired active immunity. Persons with severe immunodeficiency may be given antibody-containing serums or immunoglobins from a person or animal.

Many cells and chemicals that are part of the immune system work to destroy foreign substances as they enter the body. Macrophages circulate throughout the body and digest any foreign substances they run into. Interferons are chemicals released when a cell is attacked by a virus. These and other chemicals signal surrounding cells to shut down and prevent the virus from spreading. Lymphocytes are a type of white blood cell that produces antigens that respond to specific viruses. So, if you had chicken pox as a child, then your body will produce antibodies to protect you if the chicken pox virus enters your body again.

The state of the environment also plays a role in disease transmission. For example, the changing weather patterns associated with global warming affect disease patterns. The increased rainfall and flooding in some areas has increased the populations of a major carrier of disease—mosquitoes. The warm winters and hot dry summers in many areas are also affecting the transmission of vector-borne diseases; for example, ticks spread Lyme disease and bacteria spread cholera. There is significant evidence that outbreaks of Ebola are related to unusual patterns in the wet or dry cycle. Increases in international travel have also increased the spread of diseases worldwide. In the United States, emerging diseases such as West Nile Virus cause severe illness and sometimes death (World Health Organization, 2011). As diseases spread, or new diseases are recognized, fear of a major epidemic has caused public health agencies to prepare plans for mass epidemics or bioterrorism events.

Disease Transmission Routes

• Airborne (coughing, sneezing).
• Fecal-oral transmission (improper hand washing contaminating food, untreated sewage contaminating water supply).
• Waterborne (drinking, swimming, eating, improper hand washing).
• Direct contact (athlete’s foot, warts, STDs).
• Zoonoses (animal bites, scratches, meat, hides, feces).
• Vector-transmitted (insects, rodents).
• Soil contamination (landfill leaching).
• Fomite (transferred from inanimate objects like handrails, doorknobs, grocery carts, clothing, toys).
• Nosocomial (transferred from health workers). (Hilgenkamp, 2006, p. 54).

Environmental Health

As the human population and technology have grown, our impact on the environment—and subsequently, on our own health—has also grown. The World Health Organization (2014) defines environmental health as “all the physical, chemical, and biological factors external to a person, and all the related factors impacting behaviors. It encompasses the assessment and control of those environmental factors that can potentially affect health. It is targeted towards preventing disease and creating health-supportive environments. This definition excludes behavior not related to environment, as well as behavior related to the social and cultural environment, and genetics.”

To understand environmental health, we must first understand the environment and its many interrelated systems. We do not often think about the Earth beyond what we see around us every day, but the environment spans from the core of the Earth to the outer reaches of the troposphere. The four main divisions of the Earth system are the lithosphere (crust and mantle), hydrosphere (water), atmosphere (gases surrounding earth), and biosphere (area supporting life). Life on Earth depends on the biogeochemical cycles that occur within each of these regions. Biogeochemical cycles recycle energy and chemicals through the lithosphere, hydrosphere, atmosphere, and biosphere. Within the biosphere there are specific divisions called biomes. Biomes are characterized by similar climate, soil, plants, and animals. Because humans dominate most ecosystems on Earth, we have a large impact on the environment. Overpopulation and demands on natural resources can degrade the environment. Since the environment provides us with so many resources such as clean air, clean water, and nutrients, environmental degradation directly influences human health.

Environmental scientists and government officials look for ways to preserve the environment and conserve environmental resources. By monitoring human demand on the environment, laws such as the Endangered Species Act, Clean Air Act, and Clean Water Act have worked to protect the environment for future generations. While technology has created many problems for the environment, it is also being used to benefit the environment and human health. New farming techniques, waste management methods, and pollution control devices all help to keep the environment healthy and protect human health. Environmental health is everyone’s responsibility. Public health officials and governmental leaders are on the front lines, but the decisions made daily by businesses and individuals directly affect our health and the health of the environment.

References

Hilgenkamp, K. (2006). Environmental health: Ecological perspectives. Sudbury, MA: Jones and Bartlett.

World Health Organization. (2011). West nile virus. Retrieved from http://www.who.int/mediacentre/ factsheets/fs354/en/

World Health Organization Regional Office for Europe. (2014). Environmental health. Retrieved from http://www.who.int/topics/environmental_health/en/

Demonstration of Proficiency

By successfully completing this assessment, you will demonstrate your proficiency in the following course competencies and assessment criteria:

• Competency 1: Assess basic environmental health principles, theories, and issues.
  • Analyze an emerging or reemerging disease.
  • Describe how an emerging disease is transmitted.
  • Describe the incubation period of an emerging disease.
  • Describe how an emerging disease is treated.
  • Predict prognosis of recovery and residual effects of an emerging disease.
  • Assess the role of vaccines in disease prevention.
• Competency 4: Communicate effectively in a variety of formats.
  • Write coherently to support a central idea in appropriate format with correct grammar, usage, and mechanics.

Preparation

Select one emerging or reemerging disease to research for this report. Note: You may use the WHO Infectious Diseases and CDC websites (both linked in Resources: Diseases and Pathogens), which list a variety of relevant diseases.

Instructions

To begin, select one emerging or reemerging disease to research for this report.

Then, craft a 3–4-page report that analyzes the disease and addresses the following points:

• Provide a brief historical account of the disease selected. Consider why this disease is emerging or reemerging.
• What areas of the globe are currently affected by this disease?
• How is it transmitted?
• What is the incubation period?
• What is the treatment for this disease?
• What is the role of vaccines in combatting this disease? If there is no vaccine, why not?
• What is the predicted prognosis of recovery and residual effect?

Your report should be logically organized around a point you would like to make regarding the emerging or reemerging disease you select. Consider the MEAL Plan to help organize your thoughts:

• Main Idea: What is the main point or idea that you want your reader to remember about this disease?
• Evidence: What does the research say? Support your point with evidence from the literature you have researched. (This is where you would include facts about the history, transmission, incubation, treatment, and prevention of the disease. Refer to your sources when you provide your evidence.)
• Assess: Summarize main ideas from articles related to the disease. Apply health principles and theories that relate directly or indirectly to your main point. Make explicit links between source articles and your current report.
• Link: Integrate and combine information from your source articles to your main point or idea.

Additional Requirements

Use the APA Paper Template (linked in Resources: Writing, Research, and APA) to format your report.

• Written Communication: Written communication should be free of errors that detract from the overall message.
• Length: This report should be 3–4 pages in content length. Include a separate title page and a separate references page.
• Font and Font Size: Times New Roman, 12-point, double-spaced. Use Microsoft Word.
• APA Formatting: Resources and in-text citations should be formatted according to the current APA style and formatting.
• Number of Resources: You are required to cite a minimum of 2 scholarly resources. You may conduct independent research for resources and references to support your report. Provide a reference list and in-text citations for all your resources, using APA format. You may cite texts and authors from the Resources.