We’re exposed to new and more infectious diseases.


As climate change expands the zones for mosquito and tick borne illnesses, these carriers gain the capacity to infect us with new diseases.

How is the environment changing?

  • There is evidence that climate change is expanding the habitat and impact of the black-legged tick and the diseases it transmits in the Eastern and Central U.S and up into Canada.

Source:  Interview with Dr. Rick Ostfeld, Cary Institute of Ecosystem Studies, May 3, 2017.

  • Temperature increases and longer warmer seasons have increased the geographic range and the length of the active mosquito season for the Asian Tiger mosquito, which is a carrier of Zika and other diseases.  This mosquito also thrives in urban environments, increasing the chances of human encounters.  

Source: Manore et al, Defining the Risk of Zika and Chikungunya Virus Transmission in Human Population Centers of the Eastern United States, PLOS Neglected Tropical Diseases, January 17, 2017.

 How is our health affected?

  • The incidence of Lyme disease is increasing across the United States.  In 1995 the number of reported cases of Lyme disease was approximately 12,000.  By 2015 that number had risen to approximately 27,000, more than double.

Source: https://www.cdc.gov/lyme/stats/graphs.html.

  • Lyme is the fastest growing animal-borne disease in N America, increasing in numbers and spreading to new regions.

Source: Centers for Disease Control and Prevention. Lyme Disease: Data and Statistics: Maps- Reported Cases of Lyme Disease – United States, 2001-2014. Accessed 08/02/17. https://health2016.globalchange.gov/vectorborne-diseases

  • There is significant outbreak potential for Zika in temperate U.S. cities (NYC, Philadelphia, Washington DC and Atlanta). Up to 50% of infectious travelers returning to the U.S. could initiate local transmission in temperate cities.   

Source: Manore et al, Defining the Risk of Zika and Chikungunya Virus Transmission in Human Population Centers of the Eastern United States, PLOS Neglected Tropical Diseases, January 17, 2017.


Increased water temperature and pooling will lead to more waterborne illness.

 How is the environment changing?

  • With rising sea surface temperatures, there is an increase in the growth rates of some bacteria. For example, vibrio growth rates are highly responsive to rising sea surface temperatures, especially in coastal waters that have high levels of dissolved organic carbon.  

Source: Vezzulli, L. B., Ingrid; Pezzati, Elisabetta; Reid, Philip C.; Colwell, Rita R.; Höfle, Manfred G.; Pruzzo, Carla, 2012: Long-term effects of ocean warming on the prokaryotic community: Evidence from the vibrios. The ISME Journal, 6, 21–30.

  • Rising ocean temperatures have expanded the range of, and intensified, the harmful algal blooms in the North Atlantic and North Pacific oceans. Some of these cause the human health syndromes paralytic and diarrhetic shellfish poisoning.

Source: Gobler, C. J., Doherty, O. M., Hattenrath-Lehmann, T. K., Griffith, A. W., Kang, Y., & Litaker, R. W. (2017). Ocean warming since 1982 has expanded the niche of toxic algal blooms in the North Atlantic and North Pacific oceans. Proceedings of the National Academy of Sciences, 114(19), 4975-4980.

  • Extreme participation, which with climate change is predicted to happen with greater frequency, is a key factor for waterborne disease because it increases levels of pathogens in treated drinking water supplies and causes incidence of gastrointestinal illness in children.  

Source: Uejio, C. K., S. H. Yale, K. Malecki, M. A. Borchardt, H. A. Anderson, and J. A. Patz, 2014:  Drinking water systems, hydrology, and childhood gastrointestinal illness in central and northern Wisconsin. American Journal of Public Health, 104, 639-646. doi:10.2105/ajph.2013.301659

Source:  Drayna, P., S. L. McLellan, P. Simpson, S. -H. Li, and M. H. Gorelick, 2010:  Association between rainfall and pediatric emergency department visits for acute gastrointestinal illness. Environmental Health Perspectives, 118, 1439-1443. doi:10.1289/ehp.0901671

How is our health affected?

  • Reported rates of infections from Vibrio pathogens in ocean water have tripled since 1996. These pathogens cause illness ranging from gastroenteritis to septicemia or bloodstream infection.

Source: Newton, A. . K., M.; Vugia, D. J.; Henao, O. L.; Mahon, B. E., 2012: Increasing Rates of Vibriosis in the United States, 1996-2010: Review of Surveillance Data From 2 Systems. Clinical Infectious Diseases, 54, S391–S395. 

  • A toxic algae bloom in Lake Erie required shutting down the water supply in Toledo, Ohio, causing nearly 500,000 residents to lose access to drinking water.

Source: City of Toledo, 2014:  Microcystin Event Preliminary Summary. 73 pp., City of Toledo Department of Public Utilities

  • The Milwaukee Cyptosporidium outbreak in 1993, which was the largest documented waterborne disease outbreak in US history, causing 430,000 illnesses and more than 50 deaths, was preceded by the heaviest rainfall event in 50 years.

Source: Patz, J. A., S. J. Vavrus, C. K. Uejio, and S. L. McLellan, 2008:  Climate Change and Waterborne Disease Risk in the Great Lakes Region of the U.S. American Journal of Preventive Medicine, 35, 451-458. doi:10.1016/j.amepre.2008.08.026 

  • Other toxic algae species cause illness and death of fish, seabirds, mammals, and other marine life, often via toxin transfer through the food web. Human consumers of seafood contaminated by these toxins might also be poisoned, suffering acute toxic symptoms and even fatalities in extreme cases.

Source: Anderson, D. M., Cembella, A. D., & Hallegraeff, G. M. (2012). Progress in understanding harmful algal blooms: paradigm shifts and new technologies for research, monitoring, and management. Annual review of marine science, 4, 143-176.

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