>>Here is something you probably don't have to think about too much: diarrhea. For us
it's a nuisance that we experience after eating something that doesn't sit well with us, but
diarrhea is not really a disease but a symptom of a disease. The most common cause of this
symptom of diarrhea is a virus that infects the gut. The infection usually lasts for a
couple of days or so, and can be treated in this country with an over-the-counter medication.
But if you are a mother with a child in a developing country, you will look at diarrhea
quite differently. Not long ago, as we stated in the introductory video, a child died from
diarrhea about every 15 seconds. Because of progress that has been made towards the Millennium
Development Goals for clean water, that number is now up to about one child every 40 seconds.
But that still means that an estimated 800,000 children younger than five years of age perish
from diarrhea each year, or about 2200 children every day, mostly in developing countries
as a result of diarrheal diseases. The only bigger killer of children is pneumonia.
Well, the three things that we talked about in the last lecture: unsafe drinking water,
inadequate availability of water for hygiene, and lack of access to sanitation together
account for nearly 85 or 88% of these deaths from diarrheal diseases. Worldwide millions
of people are infected with diseases that are water or hygiene related, such as Guinea
worm disease, Buruli ulcer, trachoma, and schistosomiasis. These diseases are most often
found in places with unsafe drinking water, poor sanitation, and insufficient hygiene
practices. We call these diseases infectious diseases because it can be caused, they can
be caused by transmission from one infected person to another. The pathogenic organism
that passes from one person to another is one of the pathways we've already talked about.
In fact, a person may be infected with the disease and pass it on without ever suffering
or showing the symptoms of the disease. You may have heard of a woman named "Typhoid Mary."
Her real name was Mary Malone, an immigrant from Ireland back in the early 1900s, who
was a carrier of typhoid fever but showed no symptoms. She worked as a cook in New York
City for several years, but she was a carrier of typhoid bacteria to various family households
in which she lived. It has been estimated that three deaths for certain were pinpointed
to "Typhoid Mary," and some say as much as 50. As she got older, she changed jobs. She
even changed her name, and eventually she died of pneumonia at the age of 69, but she
herself never developed typhoid.
Let us look now more deeply into the four categories of diseases in which water can
play a critical role. I'd like to talk about each one of these categories by describing
them, giving a few examples, and then showing some preventative strategies that we can do
against them. So the first category is waterborne diseases. These are diseases that are transmitted
through drinking contaminated water. These are the ones you've probably heard about the
most: diseases such as cholera, typhoid, or infectious hepatitis. The way to prevent these
diseases, of course, is to improve the quality of drinking water so that people have clean
water without these bacteria in the water.
A second category is water-washed disease, a disease whose transmission can be reduced
with large quantities of clean water and that the emphasis here is in quantities. For example,
cholera also fits into this category because the way to treat it is to provide lots of
quantities of water for people to flush out their bodies and to replenish dirty water
with clean water. A nice movie called "The Painted Veil" featured a doctor who went to
China to treat people who were suffering from cholera, and it tells a lot about how this
disease can be prevented. Other diseases in this water-washed category are fungal skin
infection and lice infection. We just need lots of clean water with which to wash and
to treat.
A third category is water-based diseases. These are diseases in which the pathogen spends
all or part of its life in a water snail or another aquatic animal. Examples of these
are schistosomiasis or Guinea worm disease. The way to prevent these diseases from recurring
is to avoid contact with contaminated water and to reduce the water pollution that allows
these organisms to live and to thrive.
And then finally, a fourth category is water-related insect vectors. And you're also familiar with
these types of diseases. Malaria, dengue, yellow fever and tsetse fly disease are all
caused by either mosquitoes or other flying insects that either breed in water or bite
near water. So the way to strategize against this type of disease is to remove stagnant
water, to take away breeding places or, and/or to use mosquito netting to avoid being bit
by these insects.
Now some of these diseases are strange to our ears and we have no concept of them or
how serious they are. For example, the Guinea worm disease is one that we don't have to
deal with in this country, but it's an extremely painful parasitic infection that is spread
through contaminated drinking water. It is characterized by threadlike worms that slowly
emerge from inside the human body through blisters. The infection affects poor communities
in remote parts of Africa that do not have safe water to drink. In 2005, about 10,000
people were affected with this, but now about fewer than 5,000 cases were reported, and
most of these were from the country of Sudan.
Trachoma is the world's leading cause of preventable blindness and results from poor hygiene and
sanitation. Approximately 41 million people suffer from active trachoma, and nearly 10
million people are visually impaired or irreversibly blind as a result of this disease. Trachoma
can be prevented through increased facial cleanliness with soap and clean water and
improved sanitation.
So what's important to note about all these diseases is that they are easily preventable.
Again, we go back to clean drinking water, sanitation, and hygiene. Let's look once again
at that F diagram. Let's modify it slightly to show that the carrier of an infectious
disease is not always the same as the future victim. Remember "Typhoid Mary" is in that
case. The carriers of potential disease may not be showing symptoms, but still could infect
people living downstream or nearby, an important thing to remember with infectious diseases.
What is the global burden of disease? We don't think much in this country about diseases
associated with water. We generally enjoy plenty of clean water for drinking, for cooking,
for personal cleanliness. But in many countries of Africa and of Southeast Asia and of Pakistan
and Afghanistan, the percentage of deaths related to water sanitation and hygiene is
over 10%. That is an enormous burden to bear, especially since these kinds of diseases are
entirely preventable. And of that total burden, the top three are diarrheal diseases, which
account for about 39%: notably cholera, typhoid, dysentery; consequences of malnutrition about
21%; and malaria about 14%. Even in the cases that do not result in death, this often affects
nutrition and good health. And people's ability to work, to attend school, and to look after
themselves and their families becomes impaired.
I'd like to leave you today with an image from some of my travels in Cambodia. I was
walking through some of the poor villages in Cambodia, and every once in a while you
would see someone lying back in the hut by themselves. And I'd ask the children, "Well,
who is that lying in the hut?" And they would say, "Oh, that's that's our aunt or that's
our grandmother. And I would say, "What's wrong with her?" "Well, she's sick. She's
not feeling very good." On one occasion we just happened upon her and got a little bit
closer to her, and and we noticed that there was nobody around her. She was by herself.
She was isolated, and I think that's a good image of what these people have to go through
when they are sick from water-related diseases. There's nothing to do for them except let
the disease take its course, and so they're left alone. They're left isolated, kind of.
The world, life moves on around them, but they're left alone in misery. When we deal
with these diseases of water, sanitation, and hygiene, we're trying to alleviate people's
misery, and so it's important for us to learn so much more about these diseases as they
are associated with water.