Contents - Akademi Sains Malaysia

C.P. Ramachandran: Climate Change — Environment and Infectious DiseasesRemember the SARS outbreak a while back? Remember the chaos it created for international travel? In Asia, at least,air travel almost came to a standstill. Then, came H1N1. Again, the tourism trade suffered.As of 2008, mankind is confronted by 346 generic infectious diseases, disributed in a seemingly haphazard fashionacross 220 about countries. An average of three new diseases are described every two years and a new infecting organismspublished every week. Over 1600 human pathogens have been reported, each with a specific set of phenotypic, genomicand susceptibility characteristics which must be confronted by diagnostic laboratories and clinicians.The present global emergence of infectious diseases is clearly associated with the social and demographic changes of thepast 50 years, particularly urbanization and globalization, with attendant spread of pathogens via infected human hosts andvectors. It is through human activities that the levels of greenhouse gases in the atmosphere have increased at the alarmingrates. Experts now agree that the consequent warming of the world by the uncontrolled release of such greenhouse gases isnow the most serious threat to the sustainability of the human race.The changes in the environment caused by human activities are also apparent in the transformation of much of ourlandscape and conversion of regional systems once dominated by natural ecosystems. Factors include expansion intourban or peri – urban habitat, deforesation and the spread of intensive farming. The environment’s role in the emergenceof diseases is apparent in the connections between the direct consequences of human changes to urban and rural irrigatedagriculture for example, can create breeding grounds for mosquitoes and snail vectors. Likewise, the inadequate stormdrainage and sewerage systems often associated with rapid urbanization not only increases the breeding habitat for diseasevectors but facilitate the spread of water borne pathogens causing diseases like cholera, leptospirosis and other protozoanand bacterial infections. Overwhelming evidence points to human demographic changes and environmental degradationas major direct and indirect factors contributing to the increase in infectious diseases along with temperature increase dueto climate change.The UN GEO year book report links the emergence of many of the diseases like malaria, Japanese encephalitis, dengueand others transmited by mosquitoes to sullage water stagnation. Increasing level of rubbish and solid wastes in developingcountries — as a result of increasing consumerism, poor collection and refuse handling services, fly tipping, lack ofrecycling schemes and inadequate disposal sites — all aggravate the problem. Discarded plastic bags, old tin cans andcar tyres offer, when filled with rain water, perfect breeding sites for disease carrying insects. Increased and unplannedurbanization, lack of proper waste-water management schemes in many developing countries and population growth arealso important factors in the spread of these diseases.Poverty, poor living conditions, including lack of proper sanitation along with lack of infrastructure for water and solidwaste management, increase the opportunities for vector-borne and water-borne diseases to be transmitted from humans tohumans and animals to humans. The geographic spread of Aedes aegypti and Aedes albopictus into peri - urban and urbanareas throughout the world spreading dengue, chikunguyaand other virus diseases is a good example of how a potentialvector of viral diseases has taken advantage of man made environmental changes.Climate change represents a potential environmental factor affecting disease emergence. Shifts in the geographic rangesof hosts and vectors, the effect of increasing temperature on reproductive development of vectors and pathogens along withclimate variability on flooding and droughts have all a positive or negative influence on the incidence of infectious diseases.Thus climate change may aggravate the treat of infectious diseases in many ways.A working group on land use and changes and infectious diseases ranked 12 environmental factors which influence thepublic health impact on the prevalence and transmission of diseases. They being:1. Agriculture development2. Urbanization3. Deforestation4. Population movement5. Introduced species or pathogens6. Biodiversity loss7. Habitat fragmentation8. Road building9. Climate change10. Impact of HIV/AIDS11. Water and air pollution12. Irrigation and dam building.75