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NATIONAL ACADEMY OF SCIENCES-NATIONAL RESEARCH COUNCIL
COMMISSION ON GEOSCIENCES, ENVIRONMENT, AND RESOURCES
BOARD ON ATMOSPHERIC SCIENCES AND CLIMATE
Proposal No. 96-CGER-023-01
Proposal to the
Environmental Protection Agency
A Study of Climate, Infectious Diseases, and Health
This proposal is submitted by the National Academy of Sciences, which assumes full technical and financial responsibility under its Act of Incorporation for the work to be performed under any award resulting from this proposal.
David P. Westorook
William A. Sprigg, Director
NATIONAL ACADEMY OF SCIENCES-NATIONAL RESEARCH COUNCIL
BOARD ON ATMOSPHERIC SCIENCES AND CLIMATE
Proposal No. 96-CGER-023-01
CLIMATE, INFECTIOUS DISEASES, AND HEALTH
Relationships between climate, health and general well being have been recognized for hundreds and possibly thousands of years. Connections between infectious disease vectors (and other pathogens) and elements of the climate system have been investigated. Some of these relationships have been quantified and applied successfully toward preventing the occurrence or spread of a disease vector or mitigating its impact on the health of people, plants, and livestock. For example, temperature and rainfall control the emergence and distribution of mosquitoes—the vector for malaria, dengue, yellow fever, and equine encephalitis. Upsurges of water-borne diseases such as typhoid, hepatitis, bacillary dysentery, and cholera have been associated with flooding and possibly El Niño events affecting many parts of the world.' These associations refer to the modulation or control exercised through weather and climate system variability. Over the past five years increasing attention has also been focused on the impact of climate change on health, food, and water supply and quality.
Investigating and quantifying relationships between weather, climate variability (monthly, seasonal, and interannual time scales), and infectious diseases and health would provide information supporting tactical decision making and the management of social and economic resources. Studying the response of disease vectors and other pathogens to decadal and longer climate and global changes would feed into strategic planning and the development of management options. Further studies are urgently needed to examine these relationships more exhaustively.
The NRC study "Climate, Infectious Diseases and Health (CIDH)" will review the evidence behind suspected links between climate and health. It will identify useful weather and climate information products and tools, such as monitoring and surveillance systems, that can be applied today in disease prevention and mitigation efforts. It will recommend a global, international research strategy to further define weather and climate connections to human health and the emergence and spread of infectious diseases (and other pathogens)
'Aperiodic warming of equatorial Pacific Ocean water (the El Niño) is connected with global-scale atmospheric circulation paners and associated weather a continent and more distant
and to develop new tools and information products. Due consideration will be given to the hosts and carriers of either the pathogen or the vector such as food, air, and water. It is expected that the study proposed will draw upon and significantly complement other national and international activities involved in climate and health such as the assessment being conducted by the United Nations Intergovernmental Panel on Climate Change, and projects being proposed under the UN Framework Convention on Climate Change and the UN Commission on Sustainable Development.
Strong interest has already been expressed by national agencies and by the World Health Organization. Other agencies, international organizations and foundations will be approached for co-sponsorship. The NRC study was approved by the Executive Committee of the Governing Board of the National Academy of Sciences (NAS), the National Academy of Engineering (NAE), the Institute of Medicine (IOM), and the National Research Council (NRC) on June 15, 1995. It has been proposed that a Committee on Climate, Infectious Diseases and Health (CCIDH) be established to carry out the study under the Board on Atmospheric Sciences and Climate (BASC) in collaboration with the IOM. Three reports and two international workshops are planned over the three year duration of the project. Other cooperating NRC units include the Board on Natural Disasters, the Board on Sustainable Development and its Committee on Global Change, the Polar Research Board, the Office of International Affairs, the Commission on Life Sciences; and the Commission on Behavioral and Social Sciences and Education. SCIENTIFIC JUSTIFICATION
Infectious diseases are transmitted from one person to another by actual contact or contagion or by a vector. A person's body is colonized by parasites (e.g., viruses, bacteria, protozoa, fungi, and worms). Infectious diseases constitute the major cause of death worldwide. Human health is affected by climate because people are directly sensitive to climate and susceptible to diseases whose vectors are sensitive to climate. Climate affects the survival of viruses outside the host. For example, the influenza virus survives longer in low humidity, while higher relative humidity favors the poliomyelitis virus. Viral diseases with seasonal morbidity are common in both temperate and tropical zones. Influenza A, for example, occurs primarily in winter-its morbidity is aggravated by sudden cold spells. Several enteroviruses on the other hand are most prevalent in summer. It is not clear whether the seasonality of these viruses is due to the impact of climate on the virus, the host, or both. In the case of vector borne diseases, the pathogen is transmitted to a person by another agent called the vector, such as a tick, flea, or mosquito. Climate can affect these diseases in several ways. It can affect both the infectious agent and the vector directly, or it can affect the vector by influencing the types of vegetation or intermediary hosts of the vector.
National Institutes of Health (NIH), Centers for Disease Control and Prevention (CDC). Environmental Protection Agency (EPA), and National Science Foundation (NSF). ·
It is recognized that temperature, rain, sunshine (solar radiation), wind, humidity, and soil moisture affect the emergence and spread of infectious diseases. Climatic factors provide limiting conditions for the distribution of vector-borne diseases. Weather events embedded within existing climates or future climate projections can determine the timing. outbreak and spread of disease. For example, air temperature controls the latitude and altitude distribution of mosquitoes, which are vectors for dengue and yellow fever. In the tropics rainfall controls the emergence of the anopheles mosquito, the vector for malaria. The population levels and emergence of western equine encephalitis (also mosquito borne) are correlated with snow, run-off and irrigation practices.
Upsurges of water-borne diseases such as typhoid, hepatitis and bacillary dysentery are associated with flooding; in some countries such as Chile, Peru and Ecuador, floods are often associated with El Niño events that recur on a two to seven year time frame. The northernmost distribution of vampire bats and rabies are controlled by temperature and Rotovirus diarrhea is seasonally spread across North America. Large malaria outbreaks also appear to coincide with El Niño events as do toxic phytoplankton blooms in Asia and North America. Links have been hypothesized between El Niño events and the monsoons and cholera epidemics from the Black Sea to Sebastapol and Moscow. In the southwester United States, the 1993 emergence of Hantavirus (also associated with hemorrhagic fevers in Europe and Asia) may have been linked to a six-year drought followed by unusually heavy rains that led to an increased rodent population and abundant plant and shrub growth A correlation exists over the past five or more years between warming trends and the numbers of Ixodes Ricinus and Ixodes Persuicotos ticks (vectors for encephalitis) in Austria and Irkutsk, Siberia. There are many other examples in the scientific literature. Perbaps other examples will be found in a host of apparently "new" infectious diseases, such as the Lyme disease, and some common illnesses with mysterious etiology that may be partially the result of microbial infection.
Weather and climate may play a role in the potential for foods to be involved in the emergence or re-emergence of microbial threats to human health. For example, food safety can be compromised. The majority of diagnosed cases of food-borne disease of known etiology in the United States are bacterial in origin. Any change in the conditions or practices associated with the production, storage, and distribution of agricultural commodities can affect the safety of food supply. Drought can make grains more susceptible to mycotoxin-producing fungi, which can threaten the health of both humans and livestock. To survive, most microbial species, whether pathogenic or not, must be well adapted to a particulat ecological niche and must compete effectively with other microorganisms. Unusual weather and climate conditions (e.g., prolonged dry or wet spells and climate change) can alter these ecological niches, thus enabling a particular species to abruptly emerge in a region where it was not in abundance before. Because of the relatively small amount of DNA or RNA or both that they carry, and their rapid growth rate and large populations, microbial pathogens can evolve very quickly. It would be important to forecast or project potential outbreaks that are dependent on specific weather and climate precursor conditions. In many cases, the lead time this would provide may be sufficiently long to enable preventive action.
The relationship between weather, climate variability and climate change, and the outbreak of infectious diseases is reasonably well documented in some cases, and suspected in others. Many more may be discovered after a careful review of climate variability and change and the physiology and phenology of infectious diseases, the vectors that carry the diseases and other pathogens affecting health. It is important to know when, where, and to what extent such links occur.
The CIDH study will provide a global, interdisciplinary, international research strategy to identify and understand the links between weather, climate variability and climate change, and human health. It will focus most intently on aspects of infectious diseases. The study will also identify operational climate service products and tools that can be used to forewarn and forecast the outbreak or spread of infectious diseases and other stresses upon human health such as extremes of heat or cold; assist in public education and information dissemination; and recommend collaborative monitoring, surveillance, and data management systems. The study will promote research to identify presently unknown links between pathogens and climate and to quantify the climate sensitive aspects of emerging infectious diseases and other pathogens, including their carriers and hosts. SPECIFIC OBJECTIVES
The specific objectives of the NRC-CIDH study are to:
1. Investigate, survey, and further define the known and suspected relationships between weather, climate and environmental parameters, and infectious diseases. This would include a review of the physiology and phenology of diseases and their vectors and other pathogens in the context of their response to weather, climate variability and climate change. Emphasis would be placed on conditions affecting timing, occurrence/recurrence and emergence, geographic distribution, transport or spread, and potential rate of spread;
2. Define and identify a set of research and operational tools, products, and services that would facilitate the prevention and/or mitigation of infectious diseases and other pathogens that affect human health. This would include products for the management of natural ecosystems that are niches for the diseases or their vectors or other hosts as well as managed ecosystems (e.g., agriculture) and animals (e.g., livestock). Products for public education purposes will also be identified. The types of products possible, the observations and monitoring needed and the lead time available for a potential advance warning service or system may differ along time scales for weather, climate variability (monthly, seasonal and interannual), and climate change (decadal and longer);
3. Develop an inter- and multi-disciplinary, global research strategy to expand