WILL GLOBAL WARMING MAKE TROPICAL DISEASES TRAVEL NORTH? The mean global surface air temperature is expected to increase by 1.4°C to 5.8°C by 2100, with continental regions and higher latitudes to be the most subjected. Many pathogens are sensitive to temperature, rainfall and humidity changes, thus climate warming can increase the development of such pathogens, survival rates as well as host susceptibility. Pathogens that have been restricted by seasonal temperatures can invade new areas and find new victims as the climate becomes warmer also resulting in milder winters, as described in a study in the journal “Science”. Microbial pathogens are hence expanding their range of habitat into environments which were previously inhospitable. A consequence of this is that species living in these areas, including humans, are being exposed to pathogens against which defences have not yet been evolved. The absence of necessary protection will result in the need for medical treatment of new conditions. Due to the lack of previous experience regarding these conditions, healthcare professionals risk delaying diagnosis and treatment of patients. This being said, however, a subset of pathogens might also decline due to the same reasons releasing hosts from certain diseases. The El Niño-Southern Oscillation is a natural phenomenon involving fluctuating ocean temperatures in the equatorial Pacific. Waters with higher temperatures move back and forth across the Pacific. This phenomenon is a significant force in the variations of regional climate patterns, especially in North America. Recently, changes in these events have had a detectable influence on pathogens including coral diseases, Rift Valley fever and Human Cholera. Some examples of recently emerging pathogens and diseases are Ebola haemorrhagic fever, Yellow fever, Rift valley fever and Malaria. West Nile Virus was first recorded in Uganda in 1937 and rising temperatures in the United States have created a flood-drought cycle which is an optimal environment for the mosquitoes carrying this virus. By 2002, there were 4,161 cases with 284 deaths.
The main difficulty in predicting the effects of climate change is distinguishing directional climate change from short-termed variation. For most populations, there are no detailed historical records of disease impacts on fitness. However, for humans and some species of crops, long term data does exist and shows sensitivity of pathogens and vectors to climate. Thus, it is highly likely that pathogens affecting wild populations experience similar changes. References http://climate.ncsu.edu/climate/patterns/ENSO.html http://www.cbsnews.com/news/global-warming-may-spread-diseases/ http://onlinelibrary.wiley.com.ejournals.um.edu.mt/doi/10.1111/j.13652710.2012.01355.x/full http://web.b.ebscohost.com.ejournals.um.edu.mt/ehost/detail/detail? vid=0&sid=608319c9-c5f8-4fe2-b32e9d1066120981%40sessionmgr1&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d %3d#bib1