Why southern China is a hotbed for disease development

GWEN IFILL: Next: As we have seen with recent pandemics, emerging diseases like Zika and Ebola can cross continents and oceans with uncontrolled speed.

Scientists are identifying areas where new infectious diseases are most likely to emerge, where there are high risks of animal viruses passing to humans. One of those areas is Southern China.

Hari Sreenivasan brings us this report, which was produced in collaboration with Global Health Frontiers.

DR. PETER DASZAK, President, EcoHealth Alliance: We're in Guilin in Southern China, in one of the most beautiful parts of China with these amazing limestone hills and valleys and very scenic and picturesque.

HARI SREENIVASAN: Peter Daszak is the president of EcoHealth Alliance, a nonprofit organization based in New York dedicated to protecting wildlife and public health from the emergence of disease.

DR. PETER DASZAK: The reason we're here is, we're interested in the risk of new diseases emerging out of the wildlife trade in China, just like SARS did a few years ago and just like ultimately HIV did in Africa 40-odd years ago.

If we can get to the source of where they come from and reduce the risk, we could solve a huge problem and save millions of lives, rather than waiting for them to emerge and try to mop it up afterwards.

HARI SREENIVASAN: At markets across China, like this one, people come in daily to buy chickens and ducks.

DR. PETER DASZAK: It increases the risk of a pathogen like avian flu from spreading, because you have got live chickens. If one of them is infected, it brings the virus in, and it spreads to this flock over a few hours, and then those animals are taken to all distant parts of the region.

Now, you could see this activity anywhere in the world. This is just like what happens in rural America and rural parts of Europe. But the difference is, here, we're in a hot zone for emerging diseases. This is a place where we have repeatedly seen outbreaks from poultry moving into people and spreading globally.

HARI SREENIVASAN: Natural habitats can also contribute to the spread of viruses.

DR. PETER DASZAK: We have got people fishing in the river. We have got people washing in the river. We know there is sewage coming directly from the houses into the river. There is not much wildlife here, but wild ducks will come down to this river as well and mix in and migrate with the viruses and spread them backwards and forwards into this mix.

It's a big mixing vessel for pathogens.

HARI SREENIVASAN: At a goose farm, Daszak and his team are looking for signs of avian flu.

DR. PETER DASZAK: The idea is that, if we can catch the viruses they carry here, we can prevent them going to market and potentially spreading the disease.

OK, ready.

We take swabs from the mouth, and we take cloacal swabs. We put them in viral transport medium and then ship them in liquid nitrogen to the lab for testing. Avian flu is a virus that's common in many types of birds. But especially in poultry and waterfowl, it's a real killer.

And some of these strains can also jump directly into people. So that's the problem.

HARI SREENIVASAN: Viruses that can cross over and infect humans have led to previous pandemics, including the most devastating in recorded world history, the 1918 flu, which killed more people than the First World War, more than 500 million infected worldwide, and as many as 100 million deaths over a two-year period.

DR. PETER DASZAK: We're trying to say, where is the next avian flu going to come from? Can we see it before it becomes a pandemic problem and stop it?

There you go.

I look at this a little bit like earthquakes. We know earthquakes can be devastating. We know they're pretty rare, and we know where they happen.

So, this is the same for pandemics. We know that this is a hot spot for pandemics. We know why it happens, but what we're not doing with pandemics that we are doing with earthquakes is reducing the damage initially. This has been going on for 5,000 years.

HARI SREENIVASAN: Working with EcoHealth Alliance in this part of China is field operations manager Dr. Guangjian Zhu, a biologist trained in the ecology of bats, which are known to be the source of the SARS virus.

DR. GUANGJIAN ZHU, Field Operations Manager: It's really urgent to teach people how to deal with the virus and just change our normal behavior to decrease the risk of virus transfer.

DR. PETER DASZAK: This is a big tourist cave. Shall we go?

HARI SREENIVASAN: Daszak is concerned about a bat cave that is a popular tourist destination.

DR. PETER DASZAK: You have got the Rhinolophus horseshoe bats right here in this cave with all these tourists going through.



The bats here in this cave are the same bats that carry SARS virus. Bats live in the cave all day long, because they're nocturnal. And when they're up there, they urinate and defecate, right on top of the tourists that are walking through.

And all you have got to do is be that one person to breathe in at the wrong time, and suddenly you have been infected with a virus that is not only potentially lethal to people. It could cause a future pandemic.

We sent you the samples from these bats.

HARI SREENIVASAN: Daszak and his team have used mathematical models to try to understand what is driving these diseases.

DR. PETER DASZAK: We went back to every known example of emerging disease, HIV, Ebola, West Nile virus, SARS, plotted where it originated. And we said, what are the things that are going on in those places?

The two big drivers are growing human populations, land use change, and high wildlife diversity.

HARI SREENIVASAN: Rapid global response to disease outbreaks is essential to stopping transmission and saving lives. But Daszak and his team of virus hunters believe that forecasting where outbreaks are most likely to occur is a critical part of a defensive strategy needed to prevent outbreaks before they emerge.

For the "PBS NewsHour," I'm Hari Sreenivasan.

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