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Overview


zebras


Infectious

diseases

kill more

than 17

million

people

annually.

Overview

Paul R. Epstein, M.D., M.P.H.
Harvard Medical School
Center for Health and the Global Environment

G lobal warming may have grave consequences for the future control of disease. In the coming decades, and in combination with other environmental and social pressures, the current world-wide warming trend is likely to increase the exposure of millions of pe ople to new diseases and health risks. All the indications are that this disturbing change has already begun.

Infectious diseases are currently emerging, resurging and undergoing redistribution on a global scale. In fact, according to a 1996 World Health Organization (WHO) report, at least 30 new infectious diseases have emerged in the past 20 years. Diseases tr ansmitted person-to-person, like diphtheria and whooping cough, have resurged in many countries where social structures have deteriorated. Dengue, or breakbone fever, which had essentially disappeared in the western hemisphere, has now resurged in the Ame ricas, infecting over 200,000 people in 1995. Also in 1995, the largest epidemic of yellow fever in the Americas since 1950 struck Peru, while other similar epidemics have occurred throughout West Africa.

While biological changes, underfunded public health systems, and social inequities are contributing to the emergence of infectious diseases, environmental changes, including global warming and greater weather volatility, are playing significant roles in t his global disease resurgence. Diseases involving pest species as vectors (carriers), respond most readily to environmental change, and for example, meningitis epidemics are associated with severe drought conditions. In fact, in Sub-Saharan Africa, the cu rrent outbreak is among the largest ever recorded. By mid-1996 over 100,000 people had contracted the disease, and 10,000 had died. Some new infectious diseases causing problems in the United States, such as hantavirus pulmonary syndrome and Lyme disease have not been imported, but rather emerged there.

The implications of the impacts to humans are enormous. As with most risks to human health, children and the elderly-particularly the poor-will be most vulnerable. From an international policy point of view, the resurgence and spread of diseases would str ain already fragile North/South relationships. There have been periods of uncontrollable waves of disease radically altering human civilization in the past, such as when Europe's population was devastated by bubonic plague in the Middle Ages. But even tha t problem was associated with environmental changes such as population growth and urbanization. Now, a rapidly warming climate may be the stimulus for widescale change in disease patterns.

WWF Climate Change
Campaign
Director Adam Markham
c/o World Wildlife Fund-US
1250 Twenty-fourth St., NW
Washington, DC 20037
Tel: (202) 861-8388
Fax: (202) 331-2391
E-mail: climate@wwf.org
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http://www.panda.org

Climate also plays a part in maintaining the balance between pests and the predators that prey on them and thereby act as natural biological controls of infectious diseases. For example, owls, coyotes and snakes help regulate populations of rodents involv ed in the transmission of Lyme disease, hantaviruses, arenaviruses (hemorrhagic fevers), leptospirosis and human plague. Likewise, freshwater fish, reptiles and bats limit the abundance of mosquitoes-some carrying malaria, yellow fever, dengue fever and e ncephalitis. In marine systems, fish, shellfish and sea mammals help regulate algae-some toxic, others anoxic, still others transporters of cholera bacteria. Destruction of habitat worldwide is reducing the predators, and global warming may be increasing the ability of many disease vectors to survive and reproduce.

CLIMATE CONNECTION


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