Climate change will emphasize the links between disease and poverty, with the potential of pushing developing countries back into brutal poverty.

PORTO VELHO, Brazil — One evening in Porto Velho, I joined four workers from the state’s malaria control program for an evening drive into the nearby countryside.

We left the asphalt just out of town, gunned up a steep dirt road and stopped at a sheep farm.

A small wooden shack was furnished with bales of hay and a small color television. Two sides of the porch had been turned into sheep pens. On the third, clothes hung from a line. Geese waddled in the mud.

The sun had begun to drop, and my companions fanned out and got to work. Each had a short stool, a flashlight, cups lidded with mosquito netting and a long rubber tube.

I followed their leader, a short, dark-haired man named Ernaldo Cunha Santos. He rolled up his pants, set his stool next to the shack, pulled his black cotton socks to his knees, and waited for the mosquitoes to bite.

Each time one landed he would spot it with his flashlight. With the rubber tube in his mouth, he would suck it up and blow it into a cup. Twenty minutes later, he showed me his catch.

The cup was swarming with mosquitoes. Lean and hungry, they zipped like darts from wall to wall. Santos’s tube swept across his leg, vacuuming up five at a time. He paused and gave me a look of mock forbearance. Then alerted by a sudden itching in his ankle, he turned his attention to his socks.

Even where I stood, mosquitoes were biting my wrists and knuckles. After about 45 minutes, I asked Santos how many he had caught. He gave me a thumbs-down. It had rained in the afternoon, and the mosquitoes weren’t biting as much as usual. He had caught only 120.

We piled back into the truck and drove back to Porto Velho. Together, the four men had been bitten by 390 potentially malarial mosquitoes in under an hour. The collection was a daily ritual.

The next morning Santos and his colleagues would test the insects with pesticides so the state could adapt to any signs of resistance.

The economic cost of malaria is high. The disease is both a cause and an effect of poverty.

In Africa, where it is most rampant, the World Bank estimates epidemics cost the continent $12 billion a year and slow economic growth by as much as 1.3 percent. In the countries that are hardest hit, even simple prevention measures like $5 bed nets — let alone anti-malarial drugs or robust mosquito control — are out of reach for the very poor.

“Where malaria prospers most, human societies have prospered least,” wrote Jeffrey Sachs, director of the Earth Institute at Columbia University, and Pia Malaney, an economist at Harvard, in Nature. “The extent of the correlation suggests that malaria and poverty are intimately related.”

The health care systems in richer countries are likely to be able to dampen the effects of climate change on the spread of disease, but countries in the third world will suffer the full consequences.

“Restrictions on the movement of goods could also be a source of economic and political turmoil,” wrote John Podesta and Peter Ogden of the Center for American Progress, a progressive think tank, in the Washington Quarterly.

“Pandemic-affected countries could lose significant revenue from a decline in exports due to limits or bans placed on products that originate or transit through them. The restrictions placed on India during a plague outbreak that lasted for seven weeks in 1994 cost it approximately $2 billion in trade revenue. Countries that depend on tourism could be economically devastated by even relatively small outbreaks.”

Vector-borne diseases will spread through the highlands of poor countries like Kenya, Uganda and Zimbabwe, and will chip at the progress made by emerging economies.

Subhrendu Pattanayak, an economist at RTI International, a nonprofit research corporation in North Carolina, argues that countries in the Amazon need to prevent deforestation if only to blunt the cost to the economy as malaria rises due to climate change.

“Sure we have an Africa story,” he said. “But there are countries like Brazil and India and Indonesia and Malaysia, which are not so poor, where the consequences could be pretty serious.”

In the battle against disease and climate change, Pattanayak said, it’s the middle-income countries that have the most to lose.

“Some of these are about to take off and become major global powers,” he said. “But they’re still susceptible to these outbreaks. That’s what I would worry about.”  

Forecast: The global consequences of climate change

Part 1: Why America Should Care
The Florida Keys are sinking
Can insurance cover the costs of climate change?
Who will be able to afford to live on the coast?

Part 2: The Spread of Disease
Pathogens find new habitats
Countries could backslide into poverty
How disease relates to carbon dioxide

Part 3: The Arctic Melt
Easier passage through the Arctic
A scramble for control of the Arctic
Opening the Arctic to damage

(Stephan Faris is the GlobalPost environment correspondent. His new book is "Forecast: The Consequences of Climate Change, from the Amazon to the Arctic, from Darfur to Napa Valley.")

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