NARRATOR: In the lush mountains of western Uganda,
tourists come to these dense forests
in search of rare and exotic animals.
What they don't anticipate is to come in contact
with some of the world's rarest diseases.
That's what happened to an American tourist recently
who came down with a mysterious and deadly disease
after visiting this cave known for its bats.
- We're still not exactly sure how she acquired the infection.
So we know that she did enter into the mouth of the cave,
but didn't go very deep into the cave.
NARRATOR: A team from the Centers for Disease Control
found that she'd contracted Marburg virus,
a hemorrhagic fever that causes extensive internal bleeding.
Hers was the first case to reach the U.S.
- She would have had to put her hands down.
You can imagine, it's hot and sweaty.
You know, you brush your face
to, you know, push your hair back or something,
and there's ways that you could get the virus
onto your mucous membranes
and could get very efficient virus infection.
We've slowly pieced together that Marburg,
this nasty hemorrhagic disease,
they're getting it from the bat reservoir.
NARRATOR: During the same period,
another outbreak of hemorrhagic fever
was devastating a remote village in the same region.
It was discovered to be a new strain of the Ebola virus,
which scientists believe was transmitted to humans
who ate infected bush meat.
NARRATOR: For public health experts,
the Ebola and Marburg cases in Uganda were chilling examples
of just how dangerous animal diseases could be to humans.
- One of the common factors
that links these emerging and new infectious diseases
is that all of them actually started
with an animal somewhere.
So what we call these diseases is zoonotic diseases,
diseases that are transmitted from animals to humans.
NARRATOR: Uganda lies at the front lines
for diseases that cross the species barrier.
Plague, Ebola, anthrax, tuberculosis and HIV
are all endemic here.
The CDC has made Uganda a special focus for its work.
- Uganda is also a really good example
of a hotspot for where diseases arise.
Infections due to animals
represent 75% of all the emerging infectious diseases,
and so if you're really going to tackle these diseases,
you can't just focus on people.
You need to focus on the animals,
you need to focus on the environment
and that interface where those come together
to decrease infectious diseases worldwide.
NARRATOR: The Bwindi Impenetrable Forest
lies on Uganda's southern border.
It's home to half the world's remaining population
of mountain gorillas.
We're headed into the forest
to track a new gorilla family with Dr. Gladys Kalema-Zikusoka.
She's been studying diseases in the gorillas for 15 years
and is known as the Dian Fossey of Uganda.
- Is this where they nested?
- Yes. - Over here?
I think what's so special about the great apes
is that they're so similar to us.
We share over 98% genetic material,
both with gorillas and chimpanzees,
and it means that we can learn a lot about ourselves
by studying them.
When you go to visit them in the wild,
you actually feel like you're connecting.
They look at you, you look at them,
and there's some kind of connection.
It's actually very therapeutic watching them.
And the infant gorillas are very playful, just like humans.
Like, when I see them playing, I think of my two children.
(laughs)
NARRATOR: Gladys became Uganda's chief veterinarian
when she was 26.
- I've always loved animals, ever since I was little.
And then at the age of 12,
I really decided I wanted to be a vet.
NARRATOR: The BBC even made a documentary
about her first year on the job.
- This young woman's got a fight on her hands,
but she's determined to make her mark in a tough world.
- It's choking!
NARRATOR: Nine months into the job
as the country's chief vet,
Gladys was called to treat a family of gorillas
who were suffering from a troubling new disease.
- The gorillas are losing hair
and developing white, scaly skin.
The baby gorilla had lost almost all its hair
and was very thin.
The mother, where she was carrying the baby,
had also lost a lot of hair.
And the baby was making crying sounds,
which is extremely abnormal for gorillas.
And I visited a human doctor friend of mine,
because they could have picked it up from people,
and she said it's scabies.
NARRATOR: Scabies is a minor skin infection for humans,
but gorillas were naive to the disease.
For Gladys, it was the first time she saw a human disease
jump to mountain gorillas with fatal consequences.
- This is a really good area
to show that there's no buffer zone,
and the forest cuts directly onto the hill.
So that means gorillas come out often,
because they still think it's part of their normal range,
and that's when they get in touch
with contaminated items from people.
They could even...
Like there, there's a field.
They could even just find dirty clothing on a scarecrow
which is set out to scare wild animals,
and then they get sick.
NARRATOR: Recognizing this link
between wildlife health and human health
marked a turning point in Gladys' thinking.
- It made me realize that you can't protect the gorillas
if you don't think about the people living around the park
who have very little health care.
And because we're so closely genetically related,
we can easily get diseases from each other.
The only long-term and sustainable method
to improve the gorillas' health
is by improving the health of the people
living around the park.
And not just the people, but their livestock as well.
- When we say that there's human health
or there's livestock health or there's wildlife health,
and that... we just made that up.
That's not... there's only one health.
NARRATOR: Dr. William Karesh heads the Global Health program
at the Wildlife Conservation Society.
- There's just a tiny percentage of diseases
that only affect one group.
So when we eradicated smallpox around the world,
that was a simple one because that's one of the few diseases
that only affects humans.
NARRATOR: He says the most difficult diseases
are the ones we share.
- We want to work upstream.
If animals are the source of a disease,
we want to break the chain from people from getting it.
If people are the source of disease,
we need to break the chain going that direction.
And it really does play out at the local level.
Until you get it on the ground, like Gladys is doing,
it doesn't really mean anything.
NARRATOR: We've come to a small village
near the forest boundary,
where Gladys has gathered the community
to watch a drama play about tuberculosis,
a serious problem in Uganda.
(talking happily)
- This is showing a good family and a bad family,
so that the bad family, like, threw rubbish
next to the garden and defecated.
And the gorillas came and was exposed to this.
So then the good family, which is a man dressed as a woman,
came in and cleared everything up and told them off.
(reacting)
NARRATOR: High rates of HIV/AIDS and little available health care
leave people highly susceptible to infectious diseases like TB.
Simple hygiene education can help.
- So this is a family.
They're dirty, some of them don't have shoes.
NARRATOR: But Gladys also finds volunteers
to gather samples from villagers with chronic coughs...
(coughing)
- So he says he has been coughing for about five months.
NARRATOR: ...and make sure that those
that test positive for TB follow through
with the full course of treatment.
There's a problem with the local cattle, as well.
They carry a strain of bovine tuberculosis,
which can sicken humans who drink infected cow's milk.
- These cows could carry TB and pass it onto the humans,
which would be a big shame in this community
because we are improving the health of the community.
So we're going to carry out TB testing with the samples.
And if there is any cow that has TB,
unfortunately, it has to be euthanized.
NARRATOR: She's doing all this because she knows how easily
this disease could jump to gorillas.
- So we give 10 mil or 20?
If the gorillas got TB, it would be a disaster.
TB requires daily treatment every day for eight months,
and it's impossible to do that in the forest setting.
It's easier for people to get that.
I'm just trying to record all the gorillas I've seen
so that by the end of the visit,
I can tell whether I've seen all the gorillas in the group.
We're developing an early warning system
for disease outbreaks.
If we collect fecal samples regularly,
then when there's an outbreak,
we'll be able to tell what's different
and be more informed and give a proper treatment.
NARRATOR: What began a decade ago for Gladys
as an understanding
that animal and human health are tethered together
has become a new policy for organizations like the CDC.
- We think of "one health"
as not just about human public health;
"one health" is about human and animal public health.
And increasingly, what this strategy is telling us
is we need to be working more closely
in an integrated manner with the animal public health field.
- It's like a comforting sound...
(gorilla purring)
...trying to be reassured about everybody around him.
NARRATOR: In Bwindi, Gladys remains worried.
Diseases far worse than TB
have caused major die-offs in other primate populations.
In the Congo basin, wildlife experts estimate that
more than 5,000 lowland gorillas have died of Ebola
over the last decade.
- In Congo-Brazzaville, they've had people dying of Ebola
who ate gorillas that died of Ebola.
They were very encouraged by what we're doing in Uganda,
and so now they're trying to bring the wildlife authorities
together with the public health authorities
to address these issues.
NARRATOR: Health authorities are also concerned
about the further spread of these emerging diseases.
- Once upon a time, it would have taken days, weeks, months
to go from one continent to another continent.
Nowadays, within 24 to 48 hours,
you can travel from one place to the other place
and still be incubating the disease.
So it's very easy to transmit diseases worldwide.
- Sometimes, it gets frustrating
when you're trying to promote conservation.
There's so many other pressing issues.
But what gives me hope is that by promoting conservation,
we're improving community public health
around a very remote area of Uganda.
So I think we are done here.
We can head back.