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 southwestern 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. Perhaps 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 particular 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.

GOALS

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

existing knowledge on the subject that will lead to practical applications for preventing or mitigating the occurrence and spread of infectious diseases affecting health and the management of worldwide health-service resources. Deficiencies in existing knowledge will be identified; and the climate sensitive aspects of disease vectors and their hosts, including newly emerged or emerging diseases and other pathogens, will be studied further. Also included will be the identification of observing and monitoring requirements (both in situ and possibly space based) and proposals for the development of regional and global models.

The research strategy and other recommendations developed through the CIDH study will be made compatible with current and anticipated international research and service agendas and functioning infrastructures.

For example, it may be useful to conform with international
convention when considering time scales of environmental variability
and response strategies. Compatibility will most likely be reached if
the aforementioned three weather-related time scales, suggested by the
organization of the World Climate Research Programme and inter-
national weather services, are applied. Also, the research on and the
response to any particular infectious disease or pathogen and its
vector or host/carrier could be vastly different depending on the
duration of the weather or climate impulse involved. For instance, in
response to the "normal" variability of weather (e.g., over time scales
of a few days to a few weeks) certain diseases may be more likely to
occur in certain locations at certain times. Due to species competition
and differing rates of RNA and DNA adaptation (or mutation), the
response to a prolonged (e.g., three to five years or more) dry or wet
spell or to extreme events (e.g., climate variability associated with El
Niño) could be quite different. It is possible that certain disease
vectors and other pathogens suddenly flourish in locations where they
were previously suppressed. Similarly the response to climate change
(decadal to century time scale) could be different. Under altered
global climate conditions, second and third order effects must be
considered. In some cases, entire bio-ecological zones could be
displaced, eliminated, replaced, or otherwise altered. Associated with
these changes, microbial activity could be altered with some species
flourishing, others becoming dormant or dying, and new species
emerging on account of "external" environmental stress. Further
changes could be expected in the distribution of the vectors carrying
the pathogens and other hosts.

The understanding of climate-disease links as well as the preparation and disse:mination of products could be improved through the use of existing sophisticated

environmental modeling capabilities, global and regional monitoring networks, multidisciplinary data management and analysis systems, and information communication systems. The study would also explore potential roles of existing environmental impact assessment groups such as those within the International Institute for Applied Systems Analysis and the National Center for Atmospheric Research.

BACKGROUND AND ORIGIN

On May 9, 1995 the Climate Research Committee (CRC) of the Board on Atmospheric Sciences and Climate (BASC) invited experts from the Institute of Medicine (IOM), the Centers for Disease Control and Prevention, the World Health Organization (WHO), the National Institutes of Health, the Army Institute of Infectious Diseases, the Environmental Protection Agency, the National Weather Service, the National Aeronautics and Space Administration (NASA), the National Science Foundation, and universities representing epidemiology, public health, medicine, weather, and climate. The meeting overwhelmingly endorsed initiation of an NRC study to address the issue of climate, infectious diseases, and health. It was felt that a multi-disciplinary, integrated approach would lead to results of practical and immediate benefit to humanity. On the longer term, the study would lead to a global research program to provide guidance on tactical products to be used operationally and to strategic management options for future planning.

The NRC study would complement other programs dealing with climate and health such as the Second Assessment of the United Nations Intergovernmental Panel on Climate Change, the White House symposium on the health impacts of climate change, programs of the WHO, the United Nations Environment Program, and others. New research priorities will be identified for the consideration of both the climate and medical communities as well as new applications for projects such as NASA's Tropical Rainfall Measuring Mission, the Earth Observing System, NOAA's Dynamic Extended Range Forecasting Project, the agenda to modernize the U.S. National Weather Service, the international Global Climate Observing System, the Inter-American Institute, the International Research Institute for seasonal-to-interannual Climate Prediction, the UN's World Climate Programme, the Global Change Program, the International Council of Scientific Unions' START program, and the World Weather Watch, among others.

On June 15, 1995 the Governing Board Executive Committee of the National Academy of Sciences, the National Academy of Engineering, the Institute of Medicine and the National Research Council approved the NRC study and the establishment of a committee to carry out the study.

STUDY PLAN ACTIVITIES AND OUTPUT

The Board on Atmospheric Sciences and Climate (BASC) of the Commission on Geosciences, Environment, and Resources (CGER) and the Division of Health Sciences

Policy (DHSP) of the Institute of Medicine (IOM) will establish a Committee on Climate, Infectious Diseases and Health (CCIDH) to carry out a study on the subject as described under "objectives." The committee will include U.S. and international experts in weather and climate modeling, monitoring and analysis, epidemiology, medicine, public health, ecology, and social sciences. The committee will invite experts from industry, national and international organizations and agencies, and research institutions to review and share research results and other information, and develop program plans and recommendations for further study as necessary. Committee selection will follow NRC guidelines to ensure a proper balance of views, objective study, and appropriate reporting of committee conclusions and recommendations.

The study will be carried out over a period of three years. The committee will meet three times a year to facilitate its work. Two international workshops are envisaged in order for the committee to assemble information, discuss the results of research investigations, and establish international collaboration. Small workshop planning teams may meet additionally.

Output: The first workshop would cover objectives (1) and (2) of the study. The second workshop would cover objective (3). Three reports are envisaged as the output products of the committee's work. The first report is tentatively planned for spring 1996 in. the form of a brief consensus defining the scope of the problem and a preliminary assessment of climate-infectious diseases-health relationships, together with suggestions on the types of operational and research products that are desirable and envisaged as possible. This report will be widely distributed and also represent the basic working paper for the planning and organization of the first international workshop. The output of the first workshop (the second report) will be in the form of proceedings on a state-of-the-science review of links between weather, climate variability, climate change, and infectious diseases (and other pathogens) and health. It will also identify the types of operational service products that can be produced and delivered with currently available knowledge and technology. A consensus of recommended aims and priorities for education, information dissemination, and research will be included. This scientific review/report will cover objectives (1) and (2); late 1996 is the publication target date. The committee will provide a draft research strategy as input to the second international workshop. The draft strategy, specifically addressing objective (3), will be distributed widely for preliminary review by workshop participants. The output of the workshop (the third report) would represent an internationally reviewed global research strategy. The research strategy would outline actions to be taken by the climate and medical communities as well as contain suggestions for action for the consideration of governments, policy makers and managers. This third report is scheduled for late 1997.

REPORTS

Reports resulting from the activities described in this proposal shall be prepared in