Saturday, December 5, 2009


Small bands of males chased game through the savannahs. Females dug along the forest edges for roots, and searched the bushes for edible berries. Humans lived in isolated groups, which constantly moved in search of better subsistence. Then around ten thousand years ago, human settlements sprouted in the plains. Flocks grazed in pastures and humans tended their fields. This social transition "from hunting to agriculture brought permanent settlements, domestication of animals, and changes in diet. It also brought new infectious diseases, in what scientists call an 'epidemiologic transition'" (University).

"Another of these" epidemiologic "transitions came with the Industrial Revolution. Infectious diseases decreased in many places while cancer, allergies and birth defects shot up" (University). Changes to the environment, including shifts in the variety and type of species in a location, cause the emergence of new diseases or the resurgence of old diseases that were once rare.

"Now, it seems, another epidemiologic transition is upon us. A host of new infectious diseases -- like West Nile Virus -- have appeared. And infectious diseases thought to be in decline -- like malaria -- have reasserted themselves and spread" (University). Humans across the globe are falling victim to malaria, an ancient infectious disease, which was once considered to be limited to isolated tropical regions.

According to Pongsiri, a scientist conducting research on the resurgence of infectious disease, the studies "show that emergence or reemergence of many diseases is related to loss of biodiversity." She asserts that this disturbing trend is "not just case-study specific". "Something is happening at a global scale" (University). For example, it is now known that malaria rises and spreads from deforestation. The clearing of forests results in changes to the watershed, including the creation of reservoirs where malaria-carrying mosquitoes can breed. Elevation in regional temperature due to pollution or deforestation can increase the potential habitat of the mosquitoes, causing the disease to spread.

"It is new to think about biodiversity -- and therefore, species and land conservation -- as integral to public health. Until recently, almost no epidemiologists, nor medical schools, were framing questions of human infectious disease prevention in terms of, say, habitat structure, promoting genetic diversity in non-human species, or protecting animal predators as ecosystem regulators. Human diseases, goes the conventional thinking, are best understood and treated by looking at humans."

"Now there is the beginning of a movement to bring epidemiology and ecology together," says Pongsiri.

More info:

University of Vermont. "Biodiversity Loss Can Increase Infectious Diseases in Humans." ScienceDaily 3 December 2009. 5 December 2009 .

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