Changing Ecosystems and Infectious Diseases
Because climate change is an important environmental influence on ecosystems in the United States, different regions of the country will likely experience different infectious disease impacts from climate change.1,2 Variations in air and water temperature, precipitation patterns, extreme rainfall events, and seasonality can create conditions that are more or less favorable for the spread of vector-borne diseases (diseases carried by vectors, such as ticks and mosquitoes).3,2 As the climate changes, vector populations may increase, survive over longer periods during the year, and/or expand into new areas when ambient temperatures rise.4,2 Vector-borne infectious diseases include Lyme disease, dengue fever, West Nile virus infection, chikungunya, Rocky Mountain spotted fever, plague, and tularemia. These diseases are major public health concerns.
The most common vector-borne illness in the United States is Lyme disease. Carried by ticks, the disease causes more than 300,000 human illnesses a year.5 The frequency and distribution of reported cases of Lyme disease have increased over time. In 2013, locally acquired Lyme disease cases were reported in at least 16 states.4 A complex set of interactions are involved in these increases, and studies suggest that climate change is one factor.6 Rocky Mountain spotted fever, also tick-borne, causes more than 3,000 cases of illness a year, with some resulting in death.5 Other tick-borne diseases are emerging, including ehrlichiosis, anaplasmosis, babesiosis, Powassan virus disease, and Heartland virus disease, a novel infection that can cause severe illness or death.7 Ticks capable of carrying the bacteria that cause Lyme disease are expected to show earlier seasonal activity and a generally northward expansion with increasing temperatures.2
Vermont Tick Tracker: This interactive tool encourages residents and visitors to report sightings of potentially disease-carrying ticks throughout the state. Sightings are mapped and distinguished by tick type, date, location, count, and situation (on clothing, pet, etc.). This tool enables citizens to collect data that can assist scientists in determining trends in tick seasonality.
Lyme Disease Communications Toolkit: This toolkit from the Centers for Disease Control and Prevention contains a wealth of fact sheets, public service announcements, web widgets, trail signs, and other materials to help state and local health departments prevent Lyme Disease. Materials are targeted to various vulnerable audiences. Some documents are available in multiple languages.
Mosquito-borne infectious diseases, including dengue, West Nile virus infection, and chikungunya, among others, are of increasing concern. Dengue is rare in the continental U.S. but endemic in Puerto Rico; infection results in a painful illness with fever and in rare cases can result in bleeding and death.8 West Nile virus, while causing no symptoms in 70-80 percent of those who contract it, causes febrile illness in one in five cases, and in less than one percent of cases can cause life-threatening neurologic illness.9 The first locally acquired U.S. cases of chikungunya, which rarely causes death but can cause severe disabling illness, were reported in July 2014.10
Vector-borne diseases not currently found in the U.S., such as Rift Valley fever, are also threats, especially with increasing trade and travel to tropical and sub-tropical areas.5 If, as projected, vectors expand their habitats to areas not previously associated with the diseases they transmit, people may face a higher risk of missed diagnoses. Early diagnosis can prevent the more serious long-term effects of infectious diseases such as Lyme disease, so shifts in vector habitat related to climate change may pose unexpected challenges to health systems in affected areas. Strengthening monitoring and surveillance for vector-borne and other infectious diseases is a key strategy for reducing their impact on human health.
Disease Maps: This page provides seasonal tracking of seven different vector-borne diseases: West Nile Virus, St. Louis Encephalitis, Eastern Equine Encephalitis, Western Equine Encephalitis, La Crosse Encephalitis, Powassan Virus, Dengue Fever (locally acquired), and Dengue Fever (imported). From the landing page, users can navigate to maps of current activity of each disease within the United States.
- 1. U.S. Environmental Protection Agency, cited 2014: Climate Impacts on Ecosystems.
- 2. a. b. c. d. USGCRP, 2016: The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment. A. Crimmins, J. Balbus, J. L. Gamble, C. B. Beard, J. E. Bell, D. Dodgen, R. J. Eisen, N. Fann, M. D. Hawkins, S. C. Herring, L. Jantarasami, D. M. Mills, S. Saha, M. C. Sarofim, J. Trtanj, and L. Ziska, Eds., U.S. Global Change Research Program, 312 pp.
- 3. Walsh, J., D. Wuebbles, K. Hayhoe, J. Kossin, K. Kunkel, G. Stephens, P. Thorne, R. Vose, M. Wehner, J. Willis, D. Anderson, S. Doney, R. Feely, P. Hennon, V. Kharin, T. Knutson, F. Landerer, T. Lenton, J. Kennedy, and R. Somerville, 2014: Ch. 2: Our Changing Climate. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 19–67. doi:10.7930/J0KW5CXT.
- 4. a. b. Luber, G., K. Knowlton, J. Balbus, H. Frumkin, M. Hayden, J. Hess, M. McGeehin, N. Sheats, L. Backer, C. B. Beard, K. L. Ebi, E. Maibach, R. S. Ostfeld, C. Wiedinmyer, E. Zielinski-Gutiérrez, and L. Ziska, 2014: Ch. 9: Human Health. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 220–256. doi:10.7930/J0PN93H5.
- 5. a. b. c. U.S. Centers for Disease Control and Prevention, Division of Vector-Borne Diseases, cited 2014: About the Division of Vector-Borne Diseases: Vector-Borne Threats and What We Do About Them.
- 6. U.S. Centers for Disease Control and Prevention, cited 2015: Lyme Disease Data.
- 7. U.S. Centers for Disease Control and Prevention, Division of Vector-Borne Diseases, cited 2014: Heartland Virus: What Do I Need To Know?
- 8. U.S. Centers for Disease Control and Prevention, cited 2015: Dengue.
- 9. U.S. Centers for Disease Control and Prevention, cited 2015: West Nile Virus.
- 10. U.S. Centers for Disease Control and Prevention, Division of Vector-Borne Diseases, cited 2015: Division of Vector-Borne Diseases: Chikungunya Hits U.S. Mainland.
Deer tick, by Scott Bauer, U.S. Department of Agriculture, via Wikimedia Commons