The distribution of water-borne infectious diseases is influenced mainly by the hygienic circumstance of water (Epstein, 1992; Echeverria et al., 1995; Colwell, 1996; Esrey, 1996). Water-borne diseasesincluding cholera and the suite of diarrheal diseases caused by organisms such as giardia, salmonella, and cryptosporidiumare common with contamination of drinking water quality in many countries of south Asia (Echeverria et al., 1995; Colwell, 1996; Esrey, 1996). Higher SSTs and rich nutrient load in major river deltas would support extended phytoplankton blooms in selected coastal areas of temperate and tropical Asia. These phytoplankton blooms are habitats for the survival and spread of infectious bacterial diseases. The cholera outbreak in Bangladesh during 1994 has been attributed to the presence of extended phytoplankton blooms (Colwell, 1996). The aforementioned water-borne diseases could become more common in many countries of south Asia in a warmer climate.
For preventive actions, impact assessments are necessary on various aspects such as the nutritional situation, drinking water supply, water salinity, and ecosystem damage (Kaye and Novell, 1994; Graczyk and Fried, 1998). Water-borne infectious diseases, natural disaster, environmental migration, nutritional deficiency, and environmental pollution should be major risk factors for human health (Thongkrajai et al., 1990; Pazzaglia et al., 1995, Colwell, 1996). The risk factor of diseases also will depend on infrastructure, economic conditions, the hygienic situation, and medical facilities. Risk could be reduced by awareness in the communities that are more vulnerable to instability in the future environment.
In Asia, economic and population growth will expand rapidly during the 21st century in many countries. The rapid increase in population will be accompanied by migration from rural communities to overcrowded large cities (Stephens, 1995). Disasters linked to climate extremes such as floods and droughts also would impact local and regional populations and enforce migration. The huge energy consumption by the expanding population in urban cities would result in degradation of air and water quality, whereas rapid expansion of the economy will bring about improvements in living standards, such as improved environmental sanitation, hygienic practice, and medical treatment facilities. Therefore, better understanding of the interaction among climate change and environmental and health status in communities at regional and local scales is crucial to forge physiological acclimatization and social adaptations in the future.
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