Thursday, July 24, 2014

Selected Readings on Human Health, Disease, and the Environment

The following are responses and summaries of various readings related to Human Health, Disease, and the Environment. 
Under the Weather: Executive Summary
Changes in climate can affect the movement pattern of infectious diseases due to the fact that the microorganisms and their carriers are equally prey to changes in temperature, moisture, and other environmental changes, though other diseases such as HIV or Hepatitis do not have the same causal relationship with the environment because they are transmitted through direct human interaction.  In 2001 the National Research Council was asked to study the issue of the environment, its change, and the possible effect on human health and disease.  Specifically they reviewed: 1. possible connections between the variations of time and space with respect to the climate and the transmission of disease 2. Studying the possibility of creating warning and surveillance systems for climate affected diseases 3. Investigating possible future studies on the relationship of disease, climate, and human health.  Multiple disciplines, whom usually do not work together or in similar fashion, were required for the project due to the multidisciplinary nature of the issue.  Temperature, precipitation, and humidity directly and indirectly change the life of many infectious diseases and their vectors, though they are also affected by the sanitation and health services provided within a region, the density of human or vector population, changes in ecology, and organism travel habits.  Many studies have been conducted on the effect of climate change on disease however they have not been able to account for the many variables that lie under the function of diseases and are not reliable for predicting future change.  The impact of climate change on disease has yet to be well sorted out, though many believe that global warming could have an adverse impact, however human adaptations and health services could potentially prevent or reduce such impacts.  New diseases may emerge or old diseases reemerge in newly evolved forms due to ecosystem changes.  Studies of the relationship are dependent on local, small scale which make it difficult to enlarge the results to a larger scale relationship.  Long term climate change could have a vastly different effect than short term climate change such as ENSO.  Advances in technology will allow for the analysis and more detailed studies.  Historically the strategy has been to survey and respond to disease threats, but in the future hope is for a predict and prevent strategy.  Climate forecasts and observations could be used in identifying high risk areas and preventing the or reducing their occurrence.  A general understanding of the relationship may allow for some form of early warning system at a low cost, but some may require a more costly prediction system, depending on the particular disease and region.  Systems will only be beneficial if the operating agency has the sufficient resources to act upon their results.  Climate forecasts must also be combined with meteorological, ecological, and epidemiological systems to work properly as an advanced warning system.  Public health officials and government agencies must work in conjunction with one another for the systems to have their desired effect.  The research into these relationships has only just begun and has a long road to traverse before it can become effective.  The data set involving disease, climate, and geography need be greatly increased for prediction models to even be a possibility.  The interdisciplinary collaboration in universities and private institutions need be greatly increased.  New disease will always have the upper hand in the battle, however the goal should be to reduce people vulnerability to disease.

Hippocrates was one of the first major scientists to link the change in weather and climate with the transmission of disease and human illness.  The term under the weather is taken from the idea of unidentifiable cause of sickness or a temporary illness.  The advent of microbiological study greatly aided the fight against infectious disease with many countries improving the health of their populace through using pesticides, improving sanitation and water services, and public health services since the 1960s.  Though recently infectious diseases have begun a comeback due to their fast evolution against pesticides and drugs, the emergence of new diseases, the fast travel of adaptations due to modern human behavior, and weakened resources for public health programs.  The relationships between climate and disease are difficult to establish due to the fact that the health services field has not historically used predictive models or forecasting tools, the transmission of disease can be related to non-climate factors such as ecology, biology, and societal change, and the data that has been collected is few and far between. Many studies have linked the change in climate, mostly global warming trends, with an increase in disease though at the moment there is little actual evidence for this conclusion and few of these studies consider human travel, reduced public health efforts, and the great increase in drug and pesticide resistant diseases. With an increase in the knowledge of the relationship between disease and climate it is hoped that a strategy of prediction and prevention can become a possibility in the future with a better understanding of the climate and ecology that is favorable to disease transmission.
The Past as Prologue
Hippocrates was one of the first to directly link disease to the weather rather than to the divine, though much lore had been passed down attributing illnesses to weather and seasonal changes before him.  Astrology was the science of choice for the explanation of epidemics throughout much of the first millennium.  Though with the appearance of the black death in the twelfth century this began to fall apart as a particularly effective methodology.  In the 1400s Italian officials began collecting data on the deaths of its citizens in order monitor the disease and potentially predict dangerous times and places of infection.  This time also saw an increase in the need of diagnostic medicine because people wished to not be marked as having the plague and therefore not be segregated from family, friends, and community.  Later in the 1600s an effort was made to combine the data of meteorology with medicine in relation to illness.  The 1700s saw the birth of great social reform in Europe with improved sanitation systems, water treatment services, and the attribution of particularly dangerous locations with disease and deaths.  Meteorology in the U.S. was developed around the mid 19th century in order to link disease and weather, though they would take use of the telegraph before the civil war in the belief that they could use it in the warning of future weather catastrophe and prevention of loss and death.  After World War I meteorologists began creating more weather stations, better instruments, better training methods, and the standardization of methods for internationalization of study.  With the advent of the first computers they were able to begin making predictive model systems, though it was obvious from the beginning that the slightest differences in accuracy would create great differences in the end result of the calculated predictions.  Edward Lorenz described the issue with the analogy of the butterfly flapping its wings in Brazil potentially creating a tornado all the way in Texas.  He implied that weather is a chaotic system, but its prediction, while difficult, is not impossible.  Epidemiology emerged in the mid 1800s: some studying the issue of creating safe airs, waters, and locations, while others tried to link social issues such as poverty, hunger, criminality, and occupation with disease and illness.  In the beginning the focus was either on the study of individual diseases in a lab setting or on associating disease with a particular region, time, season, or population.  1882 saw Robert Koch further define germ theory creating the first revolution in epidemiological study.  The second revolution was after World War II when the focus shifted to the environment, along with human behavior and habit.  Modern studies are more focused on the grand scheme, attempting to factor in all the potential variables.  More recently historians and meteorologists have begun collaborating in an attempt to collect data on past climate events while the epidemiology field has become somewhat more independent from medicine and public health fields and has built the tools in order to address complex health issues.

Global Climate Change – Federal Research
Over the past century the global average temperature has increased by about 0.9 degrees Celsius.  Prediction models estimate that throughout the next one hundred years the average temperature will increase anywhere from 2 to 7 degrees Celsius globally, which could result in more extreme weather more often, longer and more often hot seasons, changes in precipitation patterns, and longer harsher droughts.  Human health issues are not directly related to the change in climate, however they are made more intense by these fluctuations.  The effect that climate change could have on air and water supply and quality would be the greatest of all the potential pitfalls.  A warmer environment has many possible ill effects from past experience including, excess hospitalizations and deaths due to heat, increased allergens and asthmatic issues, increased occurrence and influence of disease from bacteria and viruses, more extreme weather, and additional indirect effects from these extreme weather events.  More people seem to die from extreme heat fluctuations than from extreme cold fluctuations.  Proper health services, sanitation, building code, and other societal factors can keep extreme weather events from being so very influential.  Agriculture can be greatly affected by climate change, though with proper technology and monitoring this can be limited.  The ever increasing average age will factor in to a greater possibility of more of the population being susceptible to the detrimental effects of climate change.  More people continue to move into urban settings and therefore will suffer more from any severe climate change as urban centers are generally hotter.  The sick, old, and poor will be most harshly affected by any possible change.  Disease could be come more prevalent and more dangerous with climate change, however more research is needed in the field to relate the two.

Black Death
The Black Death was also known in past times as the Great Pestilence or the Great Plague.  The name Black Death is derived from the color of its victims skins in the later stages and its causing of gangrene.  It is believed that the disease was spread by fleas, with the assistance of rats.  Poor sanitation conditions and high population density in cities were very influential in the great scale of its effect.  The particular disease which was at the bottom of the black plague has never been sufficiently determined but the common belief has been that of the Yersinia pestis (bubonic plague).  It is believed that the plague began in the far east and spread to Europe by the twelfth century.  The total number of casualties has been estimated at around 75 million people including 30% to 60% of the total population of Europe.  The plague ruled Europe from the 1300s through the 1800s.  The plague caused a great many social reforms to be instituted throughout Europe.  Many people attributed the Black Death to astronomical causes, while others attributed it to the actions of the Jewish community.  Thousands were killed in acts of vengeance.  The plague itself had very detrimental effects on the Catholic Church, as many of the people who cared for the plagues victims were monks or other church officials, and the church’s populace questioned why there was nothing the papacy could do to stop the spread.  The Black Death was a pandemic on a scale which has not yet been repeated, however many predict that it is only a matter of time before it happens again. 

 Readings above may have been drawn from the following sources:
Six Modern Plagues and How We are Causing Them, Mark Jerome Walters; Shearwater Books, 2003, ISBN 155963992X
Life Support, The Environment and Human Health, Michael McCally, editor, MIT Press, 2002, ISBN 0-262-63257-8
Rx for Survival,  Philip Hilts, Pengquin Books.  ISBN 0-7394-6974-6
Emerging Infectious Diseases,  Stuart A. Hill, Pearson Eductation Inc., publishing as Benjamin Cummings.  ISBN 0-8053-3955-8
Under the Weather:  Climate, Ecosystems and Infectious Disease, National Research Council, National Academy Press.  ISBN 0-309-07278-6

This article originally written November 4th, 2008 for OU IPE 3913 - Human Health, Disease, and the Environment.

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