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Climate Change and Infectious Disease

The earth's climate is changing causing the oceans and the climate to warm resulting in extreme weather patterns which have brought about an increase of infectious diseases--both new and re-emerging. These extreme weather patterns are creating extended rainy seasons in some areas, and extended periods of drought in others, as well and introducing new climates to different regions. These extended seasons are creating climates that are able to sustain vectors for longer periods of time, allowing them to multiply rapidly, and also creating climates that are allowing the introduction and survival of new vectors. .

Extreme Weather = New Diseases

“The rise of extreme weather is itself a symptom of an unstable climate. Moreover, the variance around the long-term warming trend has begun to influence biological systems, Indeed, two main effects of climate change—warming and greater weather variability-mean that millions of people worldwide face a higher risk of infectious disease”. El Nino is an extreme weather pattern that is often responsible for increased precipitation, resulting in increased flooding, creating a more promising breeding ground for a plethora of vectors that both carry and cause infectious diseases.

Another result of the warming oceans are stronger hurricanes, which will wreck more havoc on land, and in the oceans, and create more opportunities for vectors to breed and infectious diseases to flourish. Extreme weather also means stronger winds. These winds can carry vectors tens of thousands of kilometers, resulting in an introduction of new infectious disease to regions that have never seen them before, making the humans in these regions even more susceptible.

Warmer and Wetter Climates = More Diseases

Mosquito-borne diseases are probably the greatest threat to humans as they carry malaria, elephantiasis, Rift Valley Fever, Yellow Fever, and Dengue Fever. Studies are showing higher prevalence of these diseases in areas that have experienced extreme flooding and drought. Flooding creates more standing water for mosquitoes to breed; as well, shown that these vectors are able to feed more and grow faster in warmer climates. As the climate warms over the oceans and coastal regions, warmer temperatures are also creeping up to higher elevations allowing mosquitoes to survive in areas they had never been able to before. As the climate continues to warm there is a risk that malaria will make a return to the developed world.

Ticks are also thriving in the warmer temperatures allowing them to feed and grow at a faster rate. The black legged tick, a carrier of Lyme disease, when not feeding, spends its time burrowed in soil absorbing moisture. Ticks die when the climate either becomes too cold or when the climate becomes too dry, causing the ticks to dry out. The natural environmental controls that used to keep the tick populations in check are disappearing, and warmer and wetter climates are allowing the ticks to breed and grow at an alarming rate, resulting in an increase in Lyme disease, both in existing areas and in areas where it has not been seen before.

Other diseases on the rise due to extreme weather include: hantavirus,  schistosomiasis,  onchocerciasis (river blindness),  and tuberculosis.

Warmer Oceans = New Diseases

The warming oceans are becoming a breeding ground for toxic algae blooms (also known as red tides) and cholera. As the nitrogen and phosphorus levels in the oceans increase, the cholera bacteria that lives within zooplankton emerge from their dormant state. The changing winds and changing ocean currents push the zooplankton toward the coastline, carrying the cholera bacteria, which then contaminate drinking water, causing cholera outbreaks. As flooding increases there is also in increase in cholera epidemics as the flood waters that are carrying the bacteria are infiltrating the drinking water supply. El Nino has also been linked with cholera outbreaks because this weather patter warms the shoreline waters, causing the cholera bacteria to multiply rapidly.

Toxic algae blooms (red tides) are the result of a changing and warming climate. El Nino events precipitation resulting in flooding, which causes the coastal seawater to be infiltrated with runoff from the flooding land resulting in increased nitrogen and phosphorus which feed the algae and spur their growth. These toxic blooms in turn infect shellfish, which threatens the health of the millions of people who depend on shellfish for protein. Paralytic shellfish poisoning is the most common result of red tides, as was seen in the 1987 outbreak in Prince Edward Island. Ciguatera fish poisoning is also a result of red tides. Humans that ingest these infected reef dwelling fish become ill. Further, red tides are so powerful that they also cause respiratory illness simply by breathing the air near them.