In one New Guinea hilltop village the message was rooted deep in lore: If you hunt in the valley below and sleep there overnight, evil spirits will possess you, you'll become sick, and you'll die.

It was a homespun kind of malaria control in the highlands of this western Pacific island, long free of the disease-bearing mosquitoes that plague the hot and humid nights of its lowlands, said Dr. Ivo Mueller, a lead scientist at the Papua New Guinea Institute of Medical Research.

As the Earth warms, however, "malaria epidemics in the highlands are now basically happening every year," Mueller said. The threat of collapsing ice sheets and super-hurricanes dominates many discussions at the annual U.N. climate conference now under way in Bali, Indonesia. On the litany of ills linked to climate change, the slow spread of warm-weather diseases is more a quiet scourge, one whose ultimate cost remains incalculable.

"What is going to be the burden on the health care infrastructure of poor, developing countries?" asked Hannah Reid, of London's International Institute for Environment and Development, opening a panel session Wednesday in Bali on the health impacts of climate change. Forecasting those impacts can be controversial, both politically and scientifically.


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