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Climate Change and the Ecology of Infectious Disease Craig Loehle NCASI.

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Presentation on theme: "Climate Change and the Ecology of Infectious Disease Craig Loehle NCASI."— Presentation transcript:

1 Climate Change and the Ecology of Infectious Disease Craig Loehle NCASI

2 Will Warming Increase Disease? IPCC AR5 says yes Focus on vector borne disease Malaria, dengue fever examples Water borne infections This talk provides perspective, covers biology of disease

3 Historic Killers How big were/are they? Were/are they restricted to tropics? Related to climate?

4 Black Death/Plague Originated central Asia Yersinia pestis bacterium Killed 30-60% of Europe in mid-1300s Globally reduced population 20% Rats/fleas implicated as carriers Vanished on its own, but some residual infections today

5 Smallpox Earliest records from Egypt, India Spread to China, Europe, then globally Devastated Indians in Americas 300-500 Million deaths globally during 20 th Century Eliminated by vaccine

6 Influenza Constantly changing global disease 250,000 to 500,000 deaths/yr globally More in pandemic years 1918 pandemic 10 to 100 Million deaths (poor records most of world)

7 Malaria Amoeba spread by mosquitos Endemic in Russia, Scandanavia late 1800s Declined even before DDT Why? – Mosquito depends on rain barrels – Modern water supply eliminated barrels & similar – Screens in windows – Reduce transmission rate below 1, dies out

8 Malaria Recent tropical resurgence blamed on climate change But coincides with reduction of DDT spraying and with chloroquine resistance DDT, screens, netting, clean water would mostly eliminate malaria Dengue fever same behavior as malaria

9 TB 19 th Century TB huge killer in Europe Declined with rising health in Europe, US Global extent, still a menace Reduced by vaccines, healthier population

10 STDs/AIDS Obvious transmission path Global 5.4% global disease deaths (WHO) NOT related to region/climate

11 Lyme Disease “vectors” theory: deer tick Rise linked to increasing deer populations

12 Water Borne Illness Bacteria, virus, other IPCC claim: – Warmer water will increase risk – Increased flooding will increase risk

13 Water Borne Examples Cholera – Bacterium—vaccine now available – Spread in dirty water – 100-130k deaths/yr Diarrhea (3.2% of disease deaths,mostly children) Other Almost entirely cured with sanitation

14 Tropical Parasites Gives impression that tropics are disease- ridden Big problem Africa – Ex: River Blindness, Rift Valley fever Due to living outdoors, poor sanitation Still only 0.2% global mortality due to disease according to WHO

15 Summary Causes of disease – High population: transmission – Poor sanitation – Standing water (rain barrels) – Poor health (susceptible)

16 Summary Major diseases devastated the world in past No major communicable disease shows any climate preference Today biggest killers have been tamed – Vaccines – Sanitation – Health Even with this reduction in total disease, tropical diseases are minor part of total disease mortality

17 Summary The few diseases that might spread represent a tiny percent of total global disease mortality Most burden of tropical disease/parasites due to sanitation Development would do 100x more to reduce disease than would preventing a 1 deg rise in temperature

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