The following are responses and summaries of various readings related to Human Health, Disease, and the Environment.
Linkages Between Climate, Ecosystems, and Infectious Disease
Weather and climate are different ideas in similar fields of study. Weather is the measurement of temperature, humidity, precipitation, and wind daily whereas climate measures these factors over a long period of time. Climate is an average and varies with geography and time. The average temperature of an area decreases by 6.5 degrees C with every 1000 meter change vertically and decreases 5 degrees C with every 1000 kilometer change from the equator. The range with which temperature fluctuates due to the seasons is greater towards the poles, with much less change experienced near the equator. There are many climate cycles occurring from yearly to millennially and some occurring as little as every 100,000 years; these oscillations can cause temperature shifts as high as 10 degree C. Since the Industrial Revolution, and more notably in the last twenty years, the global average temperature has begun to increase yearly and is predicted to continue increasing several degrees in the next century. The basis for good predictive weather and climate models does not rest solely on the atmosphere but also in surface variations, especially the oceans. Currently weather prediction is only effective on a timescale of less than two weeks, while climate models are limited to seasonal or greater timescales. Including the effects of ocean, atmosphere, and land may make climate models sufficient for shorter timescales and weather prediction for greater timescales. With infectious disease, the number of cases that indicates and epidemic will vary with each particular disease, region, and time. Emerging disease can be due to climatic or ecological change, which causes a greater number of people to come into contact with a natural reservoir of infection. Diseases can be transmitted either directly, due to contact with an agent, or indirectly, through a natural reservoir or host. Many studies of infectious disease use the SEIR framework: S. The proportion of people who are able to become infected E. Within that same group, those who have had contact with the agent but who have not become infected I. The number of people within S group who have contracted the disease R. The number of people who have been removed from the original group S due to either death or immunity. SEIR attempts to account for the many different factors in disease studies such as population size and density, demographics, connectivity patterns, and immunity. Diseases and natural reservoirs have environmental conditions that are both favorable and not for the spread of particular diseases which include precipitation, temperature, humidity, and ultraviolet radiation. Most diseases are sensitive to changes in temperature with regards to their dissemination, replication, and movement. Climate change over the long-term may result in increased intensity and occurrence in extreme weather events, where the direct impact is obviously more deaths due to disasters, though potentially and indirectly an increase in infectious disease outbreaks. The diseases associated with flooding are well known while droughts are not nearly as studied, though a disease would not affect a crisis area should it not have been present in the system before the extreme event and had not be introduced. There are many other factors that influence disease dynamics including land use, migration of disease and hosts, the societal makeup of populations, and public health services.