[MUSIC] So it turns out that our species has spent a lot of time trying to keep their cacca out of their mouths. This picture on the left was taken by my colleague Gill Burnham and it actually is toilets made in the Roman empire by Romans, that have been sort of fixed up so that Syrian refugees today can be using them. I just love that that picture reminds us, for 2,000 freaking years we've been struggling with how to contain excreta and keep the world a sanitary place. But it wasn't until this guy on the right, Jon Snow came along that we knew for sure that ingesting feces was a really bad idea. But that's a conversation for another day. So it turns out that there are several things can induce diarrhea in the human body. Those of you who have ever had too much to drink on a Friday night, or ate way too much of some fruit might know that some times a certain toxin or chemical can induce diarrhea. There are quite a few diarrheas induced by parasites, like, cryptosporidium and giardia. Well, you all know about cholera and typhoid and many different bacteria that cause diarrhea, and then there's a host of viruses that do. And one's that I think not appreciated is, sure, toxins aren't very important, but actually most diarrheas are caused by viruses and most deaths are caused by viruses, followed by bacteria, followed by the parasitic diarrheal pathogens. And if we look at WHO's data for the major causes of death. And we look at 2015 on our left here, and look at 2000 on the right. HIV and diarrhea are the conditions that we have controlled the best and reduced death from the most among those over the past 15 years. We have made great headway on controlling diarrheal deaths. This is something those of you who are out there struggling in the public health world can be very, very proud of. And while we've made great headway, this slide is breaking the world into sort of categories by income. And you'll notice that on the left, in the poorest income countries, a respiratory infections and diarrhea are the top two killers. And on the right, in the wealthiest countries, like there's almost no infectious disease deaths, lower respiratory infections are causing some. But no diarrheal deaths virtually at all among these top ten killers. So the problem of diarrhea is very, very disproportionate in the poorest countries. We have some basic strategies for stopping the transmission of feces from one person to another. Sanitation is one, when I used the way phrase sanitation, I mean the process of containing hazardous materials. So in the West, that might mostly mean controlling hazardous chemicals. For our conversation today I'm going to focus on containing excrete, because that's the main toxic substance that is going to be in the environment when you're trying to protect the world's most vulnerable populations. Another option is giving people more water, once people get up over 5, 6, 7 liters per person per day. And they've got enough to drink, and they've got enough to cook with, the thing they do with more water is wash. And they wash their dishes, they wash where the flies land, they wash dirty hands, they wash their cloths more. And certainly more water means to prevent transmission by cleaning those various surfaces that might come in contact with our mouths, or with our food. Providing cleaner water can cut down a fecal-oral transmission when it's being transmitted through water. Personal hygiene which mostly means washing your hands at key times in particular after you defecate and before you prepare to touch food. Seems to be very protective. And there are lots of settings where food hygiene strategies prevent fecal-oral transmission. Mostly food hygiene means washing foods that might be dirty and cooking foods and getting them hot to inactivate or kill pathogens that might be inside them. So here is a review, it was the fourth in a series of reviews done during the water and sanitation decade. This was the last of them and this is looking at all the studies these folks could find in the English language that looked at one of these major kinds of interventions for interrupting fecal-oral transmission, and measured reductions in diarrhea. So the first column with numbers, starts with like number studies at the top, is how many of that kind of study they found. The next column is the median reduction in diarrhea found in those studies. Then they came up with some criteria of what studies were more epidimiologically rigorous. And so those are the number of the better studies they found. And finally the median reduction in those better studies. And you will notice down the left hand side there is the various categories of intervention. Improving water supplies, which mostly means there was hole in the ground, they covered it over and put a hand pump on it. So it probably is cleaner but maybe it's a little more efficient and getting water out as well, so maybe it's a little more water. Studies that looked at cleaner water and they actually measured the cleanliness of the water. Those are mostly chlorination studies, studies that compared groups of people who consumed more water than some other people. Studies that compare people who had a toilet or a latrine compared to those who didn't. Studies that looked at people who had water and latrines, compared to people who didn't have services for either. And finally, studies that looked at personal hygiene, primarily, washing hands. And interesting, you'll notice that sanitation has the most influence of those various interventions. And secondly, when we look back on this 1991 review, hand washing looks more important than anything having to do with water. And if we look at this picture here of Martha Washington and we think about how we might get her to ingest a little bit of feces. It's a funny thing people are really uptight about what they put in their mouths. It is hard to get some stuff into people's mouths. I supposed there could be a little bit of fecal material in a fluid when we hand Martha a glass of water or a bottle, and she could ingest it that way. We could hand her a food or she might take a food that has some feces on it. She might touch something dirty, touch her food, touch her face and get feces in that way in. Flies they sure do love feces and they love your face and they love your food. So if you believe in that whole germ theory idea I suppose those tiny little fly feet could move some feces to someone's food or mouth. And that's about it. That's maybe a duskbone born particles but otherwise it is really hard to get PCs into people mouth. If we were to let's say chlorinate water or somehow improve its quality, we would only be intervening on this bottom route of transmission. But if we give people more water, what they're going to do, they're going to wash their food. And they're going to wash their hands. They're going to wash where the flies land. They're going to intervene actually on probably those top three routes but if we get people to use latrines. If we get people to put their feces in some sort of contained area or vessel so that it's not free to move around in the environment. Well, then we're actually cutting down on the amount of feces that ends up in the water supply, and the amount of feces that is out there in the fields and ends up in food. We're cutting down on all of these routes of transmission. So from the fecal flow perspective it completely make sense that sanitation would have more effect than cleaner water or more water. There have been several recent reviews, various environmental interventions and their effect on diarrhea. The most recent and I think best of them was by Sandy CairnCross at the London School of Hygiene. And he looked at three things. He looked at the effects of hand washing with soap on diarrhea, water quality and excreta disposal, and he concluded that there was a 48%, 17%, and 36% reduction respectively. Again, suggesting clean water might be less important than hand washing or sanitation. Though it might look a little bit like there's an inconsistency between these two reviews but I actually don't think so. If we look at the amazing progress we've made in the world, an increase in the fraction of people have improved water source. You can see, if we look over the fourth to the right, the one that says least developed countries. We have made amazing progress and in the next one over the one that says developing countries. We have made amazing progress over the last twenty 25 years. Interestingly the developed countries 25 years ago most everyone had improved water and toilets and adequate sanitation services. So they haven't made much progress naturally. So wow, have we made progress on water. And if you look over to the left there are all the various regions of the world, and especially in sub Saharan-Africa most have left and in the middle in eastern Asia, wow. Has there been an enormous progress with regard to the fraction of people that have safe improved water as shown by these two bottom shaded areas on these graphs. But if we look at the progress on sanitation, let's start over there, the fourth column from the right. In the least developed countries, we have made some progress. And in the developing countries, we have made some progress but it hasn't been progress as steep and as great as was made with water. And if we look over in Africa, the column on the left, wow. We have not made much progress at all, or in Oceana. And if we look out there at the millions of people who do not have an improved water supply. First of all, most of them are in Asia and most of them are rural. That's true in Asia and Africa that rural numbers of people without improved water, out strip urban. But if we look at the number of people who do not have improved sanitation it's like twice as many. There are way more people who do not have a place to defecate as have a place to get safe water. And this is interesting, all of those reviews are telling us sanitation is more important for health than is water. And yet somehow far fewer people don't have Sanitation than have improved water. And I think there are several reasons for this. First of all in rural areas people can get by without sanitation but they can't get by without water. Secondly, in many peri-urban slums, here we're looking at the neighborhood of Kadutu in Congo, my gosh, is it crowded. Like these people have tiny little patches, four meters x four meters in which they live, and they can't Find space to make a toilet and if they do it smells really bad. So a lot of these people in this particular slump and across the world do something else. They usually trimmed down street. They poop into a bag and throw into a garbage can when they go to work. They do something else to live without a toilet. But those people can't live without water. Moreover, political authorities the world over will get a lot of popularity and thanks from a population for giving them water, and they don't get similar thanks for sanitation. It's politically expedient. It's something people are more motivated to address, getting water than getting sanitation. And moreover economically people are way more willing to pay for water than they are to pay for sanitation. So for a host reasons, we've got a problem. That problem is the movement of material from the anus of some people to the mouth of another. And whatever you want to call that material, I don't really care. But in this mass transfer process, sanitation is clearly like job number one. But somehow the political, the economic the cultural, the social forces, promoting, investing in sanitation, are not as great as they are for water. So to wrap up these first big thoughts, sanitation's probably more important than water, that's not always true, but as a default. And the more unsanitary and the extreme an area is the more one should lean towards favoring sanitation. And I think the reason why that CairnCross review review had hand washing is from more important is because she's looking at a world that's much more sanitary than the world in 1990, 30 years earlier. And therefore, since almost all the people of the world, or at least three quarters of them have toilets, or latrines, in 2010, when only half did in 1990. Many of those studies are looking at people in more sanitary environments, and therefore, hand washing becomes relatively more important. So the more developed things get, the more important hand washing and clean water become. And, finally, there's just a host of reasons why sanitation is lagging water in development globally.
