What roles do climate and climate change play in the emergence and re-emergence of infectious diseases in humans and animals? What changes have already been observed? What changes could occur in the future?
INTRODUCTION: Mary Gant, Assistant to the Director for Legislation, National Institute for Environmental Health Science (NIEHS), Bethesda, MD
DATE & LOCATION: Mon., July 10, 1995, 3:15pm - 4:45pm, Rayburn House Office Bldg., Room B369 - RECEPTION FOLLOWING
Dr. Epstein will discuss the implications of climate change and the emergence of diseases and viruses such as the hantavirus, dengue fever, ebola, cholera, malaria, and eastern equine encephalitis. These ³signals² of global change can be costly to health, commerce, tourism, and transportation.
Perhaps the most well known example of an emerging virus outbreak in the US in recent time is the ³hantavirus², which is resident in rodent populations and can be transmitted from rodents to humans. Hantavirus broke out in the southwestern US in 1993, in the aftermath of heavy spring rains following six years of drought. Prolonged drought altered the ecological balance in the southwestern US by bringing about changes in the balance between the populations of rodent predators (coyotes, owls, snakes) and rodents, while the rains led to an abundance of rodent food (nuts and grasshoppers). Rodent populations increased ten-fold from May, 1992 to May, 1993. Hantavirus was amplified and transmitted to humans as a consequence of environmental changes driven by a change in climate and climate variability.
Interannual climate fluctuations thus alter the altitudinal and longitudinal presence of many disease vectors by allowing the establishment of new breeding sites and bursts of disease carriers. Examples of such events include the 1994 drought in Puerto Rico, which led to a dengue fever upsurge (due to local securing of water). A wet spring also preceded dengue fever in Costa Rica and Fortaleza, Brazil. Changes in the underlying climate are thus likely to contribute to the redistribution of disease vectors into new latitudes and new altitudes.
While proliferating megacities and non-biodegradable containers provide the setting, the influence of climate must be viewed against the backdrop of social vulnerability. Studies in Mexico demonstrate significant correlations of dengue fever with temperature and rain. Dengue fever has also appeared at higher altitudes in Costa Rica, Colombia, and India, than previously reported, as temperatures have warmed. The National Weather Service projects climate conditions conducive for a significant increase of dengue fever in the southeastern US this summer.
Ecological effects such as road building, clearing, and deforestation have played important roles in addition to climate. In deforested areas of northern Honduras, cases of malaria rose from 20,000 in 1987 to 90,000 in 1993. In Pakistan, annual incidence of malaria is highly correlated with temperature and rainfall variations, and the distribution of epidemics correlates well with the El Nino signal. Malaria transmission in the mountains of Rwanda in 1987, an anomalously hot, wet El Nino year, represented a geographic extension of malaria in altitude. Malaria cases in Houston, Texas indicate the occurrence of malaria at higher latitudes than in recent years. Models project that future climate change will extend these conditions much further into the Northern and Southern hemisphere.
El Nino warm events are associated with upsurges of cholera in Bangladesh, typhoid, shigellosis and hepatitis in South America (after flooding), viral encephalitides in Australia, and eastern equine encephalitis in Massachusetts.
Dr. Epstein is on the faculty of the Harvard Medical School. For the past five years he has also served as director of the Cambridge Hospital multidisciplinary AIDS program, and has been involved with HIV vaccine trials. Dr. Epstein has served in medical, teaching, and research capacities in Africa, Asia, and Latin America, and has also recently coordinated and co-edited an eight-part series on health and climate change for The Lancet. Dr. Epstein is a member of the Harvard School of Public Health Working Group on Emerging Diseases, a principal author of the chapter on health effects and climate change for the WHO/WMO/UNEP/IPCC intergovernmental assessment, and is a member of the federal governmentıs Working Group on Emerging and Re-Emerging Infectious Diseases. Dr. Epstein received his bachelorıs degree from Cornell University in 1965, his MD from Albert Einstein College of Medicine in 1969, and received a masterıs degree in tropical public health from the Harvard School of Public Health in 1983. In 1986 Dr. Epstein was awarded the Community Service Award for his outstanding contributions to community health.
Since 1987 Mary Gant has served as Assistant to the Director for Legislation at the National Institute for Environmental Health Sciences (NIEHS). From 1984 to 1987 she served as a senior policy analyst with the White House Science Office. Ms. Gant also served as a policy analyst in energy science and energy policy with the Department of Energy.