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Climate Change and the Ecology of Infectious Disease

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

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Climate Change and the Ecology of Infectious Disease

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  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 20th 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 • 19th 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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