The Role of Climate Change in Spreading Disease

1. The Role of Climate Change in Spreading Disease Marie Pizzorno Dept. of Biology Cell Biology/Biochemistry Program

2. Possible Effects of Climate Change • Altered/increased ranges of insects and animals that transmit diseases • Change of seasonal infections – like influenza – to year round infections • Increase in extreme weather events that exacerbate availability of clean water • Indirect effects of loss of agricultural land and rainforests due to drought or flooding.

3. Vector-Borne Infections • Any infectious agent that uses an insect or animal to be transmitted to its hosts. • Malaria (single-celled parasite, mosquito) • Viruses transmitted by insects • Viruses transmitted by rodents • Bacterial diseases transmitted by insects or animals

4. Climate Change and Mosquitoes • Warming of the environment – • Increases the viable range of mosquitoes into higher elevations and latitudes • Boosts their rates of reproduction and the number of blood meals they take • Prolongs their breeding season • Shortens the maturation period for the microbes their transmit

5. Migration of Mosquitoes • Increasing temperatures allow mosquitoes to survive at higher elevations • Evidence of that this is currently happening in some areas Epstein P.R., Scientific American, Aug. 2000, pp50-57.

6. Increased Range - Malaria

7. Predicted Increase in Malaria Transmission Epstein P.R., Scientific American, Aug. 2000, pp50-57.

8. Hantavirus • Emerged as a new disease in the southwest US in 1993 • Drought followed by heavy rains led to an increase in the deer mouse population (related to El Niño event) • Increased contact with mice transmitted the previously unrecognized virus to humans. • Caused outbreak of Hantavirus Pulmonary Syndrome (32 deaths, 53 total infections) • Total US cases = 465 (fatality 35%) Deer Mouse

9. Spread of HPS in US

10. West Nile Virus • Transmitted by infected mosquitoes to birds and humans • First appeared in NY state in 1999 • Infected healthy adults may show no symptoms or may have a moderately severe flu-like illness. • Can cause encephalitis/meningitis in older adults with neurological complications.

11. West Nile Virus • Mild winter 1998-1999 and an early spring enabled mosquitoes to survive. • Drought in spring/summer killed off mosquito predators. • Heat wave allowed virus to mature faster. • Increased infection of birds and mosquitoes  human infections. • Torrential rains in August increased pools of water for mosquito breeding.

12. West Nile Virus - Distribution 2007 1999

13. Dengue Fever Virus • Carried by the Aedes aegypti mosquito. • First infection with one of the four strains of DFV causes a debilitating flu-like illness that is usually not fatal. • Second infection with a different strain of the virus leads to a hemorrhagic fever with a mortality of 30%. • The Aedes aegypti is expanding its range and has moved into the southern US.

14. Dengue Virus

15. Other Health Concerns • Lyme Disease – caused by a bacterium that is transmitted by ticks. • Cholera – a water-borne bacterial disease that increases after severe flooding. • Animal and plant diseases – affecting agricultural productivity. • Non-infectious diseases – such as allergies and asthma - may also be connected to increasing CO2 levels and climate change

16. Conclusions • While it may be difficult to predict the actual effect that global warming will have on the incidence and location of disease, it is obvious that the ecological changes that will result from global climate change will affect the distribution and frequency of many disease causing agents and their vectors. • See work by Paul R. Epstein at the Harvard Center for Health and the Global Environment http://chge.med.harvard.edu/about/faculty/epstein.html