New diseases arise as environments destroyed, says UNBy Michael McCarthy, Environment Editor
22 February 2005
Changes to the environment that are sweeping the planet are bringing about a rise in infectious diseases, the United Nations Environment Programme (Unep) has warned.
Loss of forests; the building of roads and dams; urban growth; the clearing of natural habitats for agriculture; mining; and pollution of coastal waters are promoting conditions under which new and old pathogens can thrive, according to research published today in Unep's Global Environment Outlook Year Book for 2004/2005.
Ailments previously unknown in human beings are appearing, such as the Nipah virus, which until recently was found normally in Asian fruit bats, according to the report.
Nipah's emergence in the late 1990s as an often fatal disease in humans has been linked to a combination of forest fires in Sumatra and the clearance of natural forests in Malaysia for palm plantations. In searching for fruit, bats were forced into closer contact with domestic pigs, giving the virus its chance to spread to humans.
Climate change in particular may aggravate the threats of infectious diseases in three ways, the report suggests. First, by increasing the temperatures under which many diseases and their carriers flourish.
Second, by further stressing and altering habitats. For example, the geographic range and seasonality of two of the world's most serious mosquito-borne infections, malaria and dengue fever, are very sensitive to changes in climate. Also, Neissseria meningitidis, a common cause of meningitis, can be spread many miles in the dusty conditions that occur following prolonged drought in the Sahel.
Third, climate change may increase the number of environmental refugees who are forced to migrate to other communities, or even countries. This in turn will also favour the spread of diseases from one location to another.Overall, it seems that intact habitats and landscapes tend to keep infectious agents in check.
The issue of environmental degradation and a rise of many new and old infectious diseases is a complex, sometimes subtle one that is causing increasing concern among scientists and disease specialists.
Many scientists are now convinced that ecological disruption, dramatic environmental change, and poor handling of human and animal wastes are playing an important part in the spread of diseases such as malaria, bilharzia, Japanese encephalitis, and dengue haemorrhagic fever.
The report is based on research by some of the leading specialists. They include Tony McMichael of the Australian National University, Bernard Goldstein of the University of Pittsburgh and Jonathan Patz of the University of Wisconsin.