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
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 UN 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.
Burden on healthcare
"What is going to be the burden on the healthcare infrastructure of
poor, developing countries?" asked Hannah Reid, of London's
International Institute for Environment and Development, opening a
panel session on the health impacts of climate
Forecasting those impacts can be controversial, both politically and
In Washington this October, for example, The Associated Press
reported that the Bush administration, which opposes mandatory
international action to rein in warming, expurgated pages discussing
such negative health effects from a US official's congressional
At the technical level, researchers in poorer nations like Papua New
Guinea often cannot find the reliable health statistics - or,
sometimes, historical temperature readings - they need to reach
"Not having quality health data that spans many decades makes the
long-term assessment of climate change impact on health rather
difficult," Dr Jonathan Patz, an international expert on health and
climate, said in a telephone interview from his office at the
University of Wisconsin.
Mueller's team, based in the highlands town of Goroka, faces that
Temperature has risen
"Whether this is already climate change - it's difficult to say
because we don't have time-series data," Mueller said. "There's no
reliable malaria data from the late 1970s to 2000. But we do know that
in the last 20 years temperatures have risen 0.6 to 0.7 degrees Celsius in the highlands."
And they know they're seeing more malaria at higher altitudes. One
statistical glimpse: In 2005 the World Health Organization said
reported malaria cases in Papua New Guinea's Western Highlands province
rose to 4,986 in 2003 from 638 in 2000 - considered minimum figures in
view of reporting deficiencies.
Two out of five Papua New Guineans live in the lush, densely
populated highlands of the equatorial country, most between the
altitudes of 1,500 meters and 2,000 meters (5,000 and 6,700 feet),
"where there's no malaria or low epidemic outbreaks," Mueller said.
"There's talk of a 2- or 3-degree temperature rise in the future," he said. If so, "perhaps 2 million
people would go from a low- or no-risk area to considerable risk."
International health authorities say more than 1 million people,
mostly African children, die each year of malaria, caused by a parasite
transmitted by the bite of the female anopheles mosquito. Tens of
millions more suffer chronically from the debilitating disease.
More heat, more mosquitoes
The parasite needs temperatures above 17 degrees Celsius to develop. As for the "vector," the mosquito, scientists
have found that even small temperature increases can produce
disproportionately large increases in mosquito populations.
The Intergovernmental Panel on Climate Change, a U.N. network of
climate scientists, has long projected that mosquito-borne tropical
diseases would spread to new areas that grew warmer. But in its latest
reports, issued this year, the IPCC panel was cautious about more
"Despite the known causal links between climate and malaria
transmission dynamics, there is still much uncertainty about the
potential impact of climate change on malaria at local and global
scales," it concluded. Malaria's range may even contract in such areas
as the Amazon, which is expected to grow drier as the world warms,
As Mueller noted, factors beyond temperature and humidity can
influence malaria's spread: population movements, deforestation,
preventive health measures and failing health systems, among other
But the malaria researcher said the bottom line is clear.
"There's no question," he said. "If you put climate change into the
equation and the climate becomes more favourable, the mosquitoes'
numbers go up and you're going to have more and more transmission."
The evidence lies not only in New Guinea. Similar highlands
epidemics have been reported in previously malaria-free areas of east
Africa, Madagascar and West Papua, on the western Indonesian half of
this island. – (Sapa)