The World Health Organization
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.
