NARRATION
Life in northern Australia is full of spectacular surprises and natural hazards, some more obvious than others.

Mark Horstman
Fires, floods, venomous stingers. Animals with lots of teeth. But there's something that hardly anyone knows anything about. It's ancient, it's practically invisible, it can kill you within 48 hours and it's living right here beneath my feet.

NARRATION
Meet Burkholderia pseudomallei. It's a native bacterium that lives in water and soil. But it doesn't stop there.

Dr Mirjam Kaestli
This bacteria is highly versatile. It manages to colonise pretty much everything.

NARRATION
And when that includes us, it causes a disease called 'Melioidosis'.

Prof Tim Inglis
Think of us as accidental consequences and being caught in the crossfire.

NARRATION
People with chronic health problems, like diabetes, lung disease and heavy alcohol use, are most at risk.

Prof Bart Currie
They're definitely deadly for unfortunately still too many people.

NARRATION
Over the last two decades, Melioidosis has claimed 107 lives in the Northern Territory, nine in the last year alone.

Assoc Prof Dianne Stephens
If you're sensible, if you don't walk around in bare feet in muddy areas, you know, if you look after any cuts and scrapes and other things that you might get while you're in the Top End, then you're not going to get Melioidosis.

NARRATION
But recent wet seasons in the north have seen more infections than ever before.

Helen Bateman
If it happened to me, it could happen to you or... your friend, your wife, your husband, your neighbour.

NARRATION
To follow the Melioidosis trail, I've come to the wild north of tropical Australia.

Mark Horstman
From here, in the Kimberley, right across northern Australia, through Darwin, into Townsville, this is the front line for Melioidosis research in the world's tropics.

NARRATION
The first step in mapping the risk of Melioidosis - find out where the microbes live. As they drive across the Kimberley, microbiologists Tim Inglis and Adam Merritt sample soil at river crossings every 100 kilometres or so.

Prof Tim Inglis
You like to draw big conclusions over a big area. We're trying to do that with an even more challenging task, which is a very small beastie you can't even see with the naked eye.

NARRATION
I'm put to work at the cutting edge of this research.

Mark Horstman
A new one for science, eh?

Adam Merritt
A new one for science - the first sample from this spot.

Mark Horstman
What might you find?

Adam Merritt
Might find the original Burkholderia. You never know. That's it. Oh, perfect! Got... nice, greeny, fine, clay, mud sort of consistency.

Mark Horstman
Good habitat for bugs.

Adam Merritt
Yeah.

NARRATION
This is the natural habitat of Burkholderia pseudomallei. The bacteria aren't trying to invade us - we just end up colliding with them.

Prof Tim Inglis
These are the sharks of the soil. They're out there, they're minding their own business, they're in a habitat that they're comfortable with, and then we go and stumble into it.

NARRATION
Studying how they coexist with other life forms, like living inside amoebae, provides clues to how they infect humans.

Prof Tim Inglis
They can survive for a very long time in water, but we think they may be able to survive even longer in amoebae. There's a possibility that's where they may have learnt how to live inside cells, such as cells of the human body.

NARRATION
Tim and Adam have put a state-of-the-art genetics lab in the back of their car, to analyse the samples for microbial DNA while on the road.

Prof Tim Inglis
These environmental pathogens are quite difficult to find, especially during the dry season. And we believe that the further you transport the samples, the more likely you are to get a false negative result. By getting the equipment into the field, we're getting closer to where those organisms are and hopefully we'll get a higher positive rate.

NARRATION
We'll return to see whether they do. On the other side of the border, the Darwin hospital is dealing with a surge in the number of Melioidosis cases.

Prof Bart Currie
There's been this big change. So, in summary, over the last three years, we've had 252 cases, which is way bigger than we would have expected from our previous figures.

Assoc Prof Dianne Stephens
The last season we had 30 patients in intensive care, and at the beginning of the 2000s, we would probably have eight or ten. So it has significantly increased. It waxes and wanes, depending on, usually, how big the wet season is.

NARRATION
It's taken Paul Griggs months to recover from the last wet season, when he was struck down by the simple act of mowing the lawn.

Paul Griggs
As you can see, rural block, a lot of grass. So there's a fair bit of mowing. I jabbed myself in the leg, which opened a wound. No, not a major issue, but given the amount of muck that had been thrown out from the mower, that's how the infection entered the body.

NARRATION
But not just gardeners are at risk. Helen Bateman believes she caught Melioidosis at her city apartment.

Mark Horstman
It's a nice spot.

Helen Bateman
Beautiful, yes. We like it. Did this for the reason that we didn't have to garden on weekends. From the Melioidosis and being so sick, I've had other issues that have arisen - kidneys, liver, pancreas. So I'm now unfortunately on insulin on a daily basis. And, yeah, so it's a terrible disease.

Mark Horstman
So it's dramatically changed your life.

Helen Bateman
Absolutely.

NARRATION
Helen's life was saved by a lengthy stay in intensive care.

Assoc Prof Dianne Stephens
We've had terrific outcomes in the last ten years, compared to the previous ten years, when most of the patients who came to intensive care with Melioidosis would die.

NARRATION
The treatment aims to kill the bacteria with antibiotics, stop blood poisoning and boost the patient's immune system.

Assoc Prof Dianne Stephens
Now we have a 25% mortality rate, down from 95% previously.

Mark Horstman
That's a dramatic decrease.

Assoc Prof Dianne Stephens
It's a dramatic decrease. We mostly see it in the lungs in intensive care, causing very serious pneumonia. But we also have to go hunting for where it's hiding, and it can be in the liver, the spleen, the kidneys... You can see all the black areas are actually areas of infection - abscesses within the liver. If you can see this really big area here - it's 7 centimetres - this big one here is what we're looking at draining.

NARRATION
There are three ways the bacteria enter the body. Through open wounds in the skin, in drinking water, or into the lungs when inhaled.

Assoc Prof Dianne Stephens
It's a very resistant and resilient little organism.

NARRATION 
They also colonise plants, and Darwin is growing grassy highways that spread the bacteria directly into the city. Weeds like Mission and Tully grass spread quickly along drainage channels and into the bush, providing ideal habitat.

Dr Mirjam Kaestli
These roots all excrete nutrients, and these nutrients are just paradise for the bacteria - it's pretty much their food.

Mark Horstman
This is the dry season in Darwin, and it should be a tough time for soil bacteria to survive. But with the spread of introduced grasses like these, that keep the soil moister for longer, the Melioidosis bacteria can thrive in the parks and backyards all year round.

Dr Mirjam Kaestli
That means that the public is now potentially more exposed to this bacteria, even in the dry season. But so far, we haven't really seen this translated into cases. Luckily we haven't seen it happening yet.

NARRATION
For more than a decade, Mark Mayo has been keeping an eye out.

Mark Mayo
I'm part Indigenous, so half the cases of Melioidosis have been Indigenous people in the Northern Territory, so it sort of relates to me and I've had family members that've had it, as well.

NARRATION
His lab at the Menzies School for Health Research cultures bacteria from hundreds of soil, water and air samples. The aim is to pinpoint the Melioidosis hotspots and find explanations for the surge in infections. Unchlorinated bore water supplies are sampled on rural properties, to try and match bacteria with clinical cases.

Mark Mayo
What we found was that out of 55 of them, 18 were positive for the presence of the bacteria. Even though that's around 30% of the water we found positive, we don't see 30% of the people living in rural areas coming in.

Prof Bart Currie
We really don't understand the environmental aspects of this organism, we don't understand about its dispersal and we actually don't understand about its virulence.

NARRATION
Another key question is the extent to which the bacteria are carried by air and dispersed by high winds and heavy rain. One theory is that soil disturbed by construction activity whipped up in the cyclone season may partly explain Darwin's increase in Melioidosis cases. It rings true for Helen, who fell sick during a cyclone.

Helen Bateman
The rain was so heavy that it actually bubbled up through this downpipe.

Mark Horstman
Strange to think that something from a cyclone could just come and...

Helen Bateman
Lob on my little veranda up here and knock me for six. Yeah.

NARRATION
There's enough capacity for airborne infection that the US lists this microbe as a potential biological weapon, along with anthrax or Ebola. Over in the Kimberley, Tim Inglis has found links between cyclone tracks and outbreaks of Melioidosis.

Tim Inglis
If, as a result of climate change, we see more of those severe weather events bringing soil and dust storms, and especially moist soil, in from the Northern Territory across Western Australia, we are going to see more cases of disease.

NARRATION
That means development in the north could have major implications for public health, with the expansion of suburbs, mining, and agriculture, such as the Ord irrigation scheme.

Tim Inglis
That irrigation scheme needs to be monitored and monitored very closely. Because if it's not managed carefully, we could end up with a number of health threats.

NARRATION
There are two global epicentres for Melioidosis - north Australia and south-east Asia, where the death rates in agricultural areas are much higher. The Melioidosis bacteria still call Australia home.

Mark Horstman
Over hundreds of millions of years, they evolved here, and moved to south-east Asia around the time of the last ice age. That's important for research, because it means that the ancient Australian strains are the ancestors to the rest of the world.

NARRATION
What we learn from the ancestral strains here, could be the key to saving lives elsewhere, by developing a simple diagnostic test, and perhaps a vaccine. At the end of the road in the Kimberley, the genetics lab on wheels confirms the presence of Burkholderia DNA, only 24 hours after sampling the soil.

Tim Inglis
Well, this is good - we've got two positives out of the four that we tested. That's a higher high rate than we normally expect.

NARRATION
Not only are there more spots on the Melioidosis map, they may have found a new strain of bacteria.

Tim Inglis
That suggests that we've got greater load of these organisms present locally, and this is a place worth looking at in much greater detail.

NARRATION
Linking microbiology in a creek bed to clinical research at a hospital bed is crucial for learning to live with the Melioidosis bug.

Assoc Prof Dianne Stephens
In the end, when the patient gets better and they come back and they say, 'Thank you very much,' that's what our job's all about, that's what makes it worthwhile.

STORY CONTACTS

Professor Tim Inglis 
Medical microbiologist, 
University of Western Australia

Professor Bart Currie 
Head of Infectious Diseases
Royal Darwin Hospital

Associate Professor Dianne Stephens 
Director of Intensive Care Unit
Royal Darwin Hospital

Dr Mirjam Kaestli 
Molecular microbiologist
Menzies School of Health Research

Mark Mayo 
Melioidosis Project Manager