Nightly News   |  December 10, 2009

As temperatures rise, mosquito-borne disease spreads

Dec. 10: Perfect Storm: A warmer, wetter climate is triggering a worldwide outbreak of mosquito-borne diseases like dengue fever; medical experts warn that more than 5 billion people could soon be at risk. NBC's Ian Williams reports from Malaysia.

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This content comes from Closed Captioning that was broadcast along with this program.

>> renewal is happening.

>>> we are back. we have a report on the intersection of the environment and health, specifically the spread of a disease that may soon include parts of the u.s. this story is also related to the climate change debate , and that global summit going on in.

>> caller: copenhagen. ian williams has tonight's report in this week's series we are calling "a perfect storm ."

>> reporter: on the front line the battle against mosquitos can be intense and personal. it feels like a war against mosquitos. but it's a war the world is losing. a warm and wetter climate is triggering more outbreaks of mosquito-born diseases. more than 5 million people could be at risk from denghi fever, as well. dengue used to be a disease of southeast asia , but now spread to more than 100 countries, including australia, africa and south america . last month it appeared in florida the first time in more than 50 years. the number of cases worldwide now tops 100 million per year with around 25,000 deaths. in malaysia, this doctor treats the most severe cases of what's sometimes called break bone disease because of the intense joint pains it can cause. there is no vaccine. the more often you have it, the more severe it can be. it's no longer a disease just of children.

>> certainly we are seeing more and more adults being admitted with dengue and with severe forms of dengue, as well.

>> reporter: never had anything like this?

>> never, ever, never in my life.

>> reporter: ground-breaking research in this laboratory confirms the potential impact of rising temperatures from climate change . it shows a rise of just 4 degrees fahrenheit can almost double the speed which the dengu virus develops in a mosquito.

>> they become very infected much faster.

>> reporter: mosquitos bite more frequently in hotter temperatures. because it breeds in stagnant water, a less predictable rainy season means it's now a year-round threat. health officials scour the city pouncing on everything from flower pots to abandoned building sites. their weapons ranging from guppies that feast on mosquito larvae to chemical fog. this has been the fight. mosquitos are becoming more resistant they have to find other ways to take them on.

>> mosquitos is adapting to the environment, but we are not adapting fast enough to these changes. this is what we have been storing over the last 30 years.

>> reporter: by examining the dna of past dengu viruses, he aims to predict how it will strike in the future. that may put a vaccine within reach.

>> there is no way we are going to use our bare arms.

>> reporter: he says we've got to get smart to defeat one of mankind's enduring enemies, whose global march is being aided and abetted by the