Every year, dengue fever claims the lives of thousands of people across South East Asia. The spread of the mosquito borne virus is traditionally blamed on lack of hygiene and poor water storage.

But now, there are new factors aiding and abetting its spread: climate change and affordable air travel are taking the virus to places it's never been seen before.

Nidhi Dutt reports.

Nidhi Dutt, reporter: Dengue fever, the mosquito borne virus, causes a high fever and excruciating body aches. Its sometimes fatal symptoms - including internal bleeding - have earned it the alternative name of break bone fever. The dengue belt stretching from North Africa all the way to Australia, and uncontrolled urbanisation, opened borders, and affordable air travel are now taking the virus and mosquito to new places.

Dr Peter Ryan, Head, Mosquito Control Laboratory, Australian Centre for International and Tropical Health: The single greatest factor that's contributed to the worsening trend of dengue is the fact that someone can be infected with dengue in one country, in one city, in one day and then the next day, be at a completely different city and transfer the virus in their blood to a different city.

Nidhi Dutt: In recent years, governments and health officials across South East Asia have grappled with an alarming spike in dengue infection rates. Last year, the region experienced one of the worst outbreaks on record.

Cambodia reported some 38,500 cases of infection and nearly 400 deaths, but the hardest hit was Indonesia. Across the archipelago, more than 1,000 people were killed by the deadly strain of the virus.

But the reach of the dengue carrying mosquito didn't stop there. Vietnam, Thailand, Malaysia and Singapore were all affected. According to the World Health Organisation (WHO), 2007 was the fourth consecutive year of unusually high infection rates and the prediction for this year is just as grim.

"The control of dengue is everyone's responsibility." Dr Prasittisuk Chusak

Dr Prasittisuk Chusak, Coordinator, Communicable Diseases Control, WHO: We have to strengthen our capacity to early detection and to provide the effective case management, that is one of the strategies that we advocate to member countries. The control of dengue is everyone's responsibility from the individual, from families, and also from the community.

Nidhi Dutt: A lack of hygiene, rubbish and poor water storage systems are often blamed for harbouring the virus, but scientists now say there's another factor influencing the rapid spread of the disease.

Dr Peter Ryan: We think that changes in rainfall or weather as a result of global climate change will not only just increase temperatures, but affect the distribution of something like the dengue mosquito. So we may in fact find that areas that have dengue now may in fact have less dengue as a result of changing weather patterns, and areas that don't have dengue now may in fact see dengue occur in the future.

Nidhi Dutt: Climate change and a lack of sustainable prevention programs have had a catastrophic impact on dengue countries like Vietnam. During last year's outbreak, authorities there reported 80,000 cases of infection and nearly 70 deaths, but these figures were nothing new. For years, the country's poor have born the brunt of deadly outbreaks.

Dr Peter Ryan: There's a greater trend in places like Vietnam now as people move from the poor rural communities into the cities to find work. And so on the outside areas of those cities, sometimes the sanitation and the water supply might not be at a high enough level to prevent mosquito breeding, so people collect water in small containers or they don't have a trash collection system, and all those disused items can collect water and those containers can breed mosquitoes.

Nidhi Dutt: But lessons are also being learned. The human and economic toll of re-occurring outbreaks has prompted authorities in Vietnam to endorse community based prevention and awareness programs.

"Once you eliminate the particular type of mosquito that transmits dengue, you find dengue disappears also." Dr Peter Ryan

Dr Peter Ryan: Last year, we went back and revisited some of those early project sites that we worked in from 1998 onwards. We obviously were interested to know whether the program has been continued, because there hasn't been any funding that's gone directly into these programs since about year 2000. We were unable to find any Aedes aegypti mosquito - that's the dengue mosquitoes in those communities - and of course, once you eliminate the particular type of mosquito that transmits dengue, you find dengue disappears also.

Nidhi Dutt: But the battle against dengue is not just limited to South East Asia's poorest countries. Singapore, the region's wealthy island state, is also battling on the same front. Last year, it suffered its worst outbreak since 2005.

Professor Leo Yee Sin, Clinical Director, Communicable Disease Centre, Singapore: We had about 6,000 cases last year and we reported about 20 deaths of dengue infections. So if the trends continue in that pattern, it's very likely that we have to anticipate that the total dengue cases this year likely to supersede that of last year. There's still yet a lot of area that we need to learn from managing the disease, as well as how we can put in measures to control the spread of dengue infection.

Nidhi Dutt: In recent years, the city state has also become a regional hub for research into vaccines and treatments for virus.

"We hope that in the next decade we'll be able to see the availability of vaccine." Professor Leo Yee Sin

Professor Leo Yee Sin: Dengue has four different types and they are four relatively different viruses. It's the greatest challenge at this point in time. Certainly, we hope that in the next decade we'll be able to see the availability of vaccine, and vaccines in the current time possibly, is the only hope that we can have.

Nidhi Dutt: The World Health Organisation says urbanisation and the rising prosperity of Asia's huge cities are key reasons for dengue's growing prevalence across the region.

But others like Brian Montgomery from North Queensland's Tropical Population Health Network says open borders and affordable air travel have played a part in the spread of the virus.

Brian Montgomery, Tropical Population Health Network: The only way dengue gets into Australia is it comes in via infected overseas travellers. So that's either people from Australia that have visited overseas coming back, or indeed tourists. So the main reason why we have dengue outbreaks in Cairns and North Queensland in general is because we have those international links with countries that have dengue present all year round.

Nidhi Dutt: This year, authorities in North Queensland's Mossman and Port Douglas areas have confirmed 20 cases of dengue fever. But with water shortages prompting more and more households across the country to install water tanks, the perfect breeding ground, authorities are on high alert.

"If water tanks are not maintained to the legal requirements, they will become breeding site for mosquitoes." Brian Montgomery

Brian Montgomery: Certainly our experience up in the far north of Queensland and the Torres Strait indicates that if water tanks are not maintained to the legal requirements, they will become breeding site for mosquitoes.

So like I said, it's definitely on the political agenda. We have the legislation in place, there needs to be some discussions as to how that would actually be policed and enforced. So I think there's definitely a need for the public in general to be educated and to be made aware that mosquitoes can be more than a nuisance issue. They can actually carry disease.

Nidhi Dutt: Two and a half million people live in areas where dengue is endemic. The virus infects an estimated 50 million people across five continents, and the World Health Organisation expects millions more will be affected in coming years.

Countries around the world are battling outbreaks with impulsive search and destroy methods, but what they really need are affordable vaccines and treatments to be able to protect the poorest and most vulnerable, the people dengue hits hardest.

Jim Middleton, Presenter: That report from Nidhi Dutt.