Rita Colwell on folding saris and saving lives

Saris are meant to be worn. But did you know that the garment can also be used to radically reduce the spread of cholera?

In 2003, environment microbiologist, scientific educator, and distinguished professor at the University of Maryland Rita Colwell conducted a study in which 7,000 women in Bangladesh were trained to filter the water they gathered every day through a cotton sari folded four times, which reduced the spread of cholera by almost 48%.

In 2008, Colwell returned to Bangladesh to see if the practice was still in use. What she found was that with no further training, 31% of participants continued to filter their water and about 60% continued to use saris for that purpose. Moreover, a significant group of women who had not learned the filtration technique had started filtering as well, taught by the population who had first received the training. And households that didn’t filter their water but lived in the vicinity of those who did had lowered their incidence of cholera.

We spoke with Colwell to learn more about how the ubiquity of the garment, the simplicity of the filtering technique, and the ease of teaching this method enabled this approach to spread throughout networks in the region.

Matlab, Bangladesh
A woman washing a sari in Matlab
  1. Matlab, Bangladesh (Image: Google Maps)
  2. A woman washes a sari in Matlab (Image: jay photog/Flickr)
We think households can provide themselves with good water that significantly reduces many of the waterborne diseases in a way that's sustainable and doesn't cost anything. It's a matter of education and individual empowerment.

PopTech: How did the sari cloth filtration study come to fruition?

Rita Colwell: We hypothesized if we could remove the particulate matter, the plankton, in a very simple way we could reduce cholera in a country like Bangladesh where it's endemic. Due to the lack of safe drinking water, the villagers – women – will go great distances to collect water. The water is untreated. Laboratory experiments showed that with simple filtration, a sari cloth folded four or five times could remove 99% of the bacteria.

We did a three year study that was funded by the NIH where we were able to show a reduction of 50% of cholera in the village where we had laid out an experimental design: those who filtered, those who didn’t, and sufficient buffer between the two groups.

PopTech: Are the techniques that were conveyed to the women and girls during the initial 2003 study in Bangladesh continuing to be used?

Rita Colwell: Yes. The question was whether this was sustainable. What I mean by that is were they continuing to do this, did they understand and did they feel sufficiently intellectually stimulated to continue filtration? We were able to go back five years later with funding provided by the Thrasher Foundation and determine through interviews that between 60% and 70% were still filtering. Most were using the technique we had introduced but we also found that control villages where we hadn’t instructed them to filter had actually begun to do so.

By analyzing the data, we discovered there was herd immunity. If you were a family that did not filter but you were surrounded by families who did, you were protected. This was because the transmission, person-to-person, was significantly reduced in that situation. We could say with great confidence that filtration played a major role in the reduction of cholera. The paper showing the herd effect and the sustainability of this initiative was published in the online Journal of the American Academy of Microbiology.

PopTech: Could you speak to the sari as a low cost behavioral solution, i.e., getting women to shift their mindset and actions and using something they wear everyday to do so. How do you get people to change their behavior and how do you educate for behavior change?

Rita Colwell: A very important part of the filtration experiment was that over the three years we conducted it, we hired extension agents, which were modeled after the agriculture extension agents in the United States. We educated the women, we taught them why filtration was important and how it could be most effective, we explained that there were bacteria, parasites, and so forth in the water that made people sick and that by following this procedure, far fewer people would get sick.

They then became the teachers. Every week, they went out to the villages to reinforce filtration. We actually made charts for them to carry that showed pictures of the kinds of microscopic animals and plants in the water that could carry these bacteria and how they could make children sick. It didn’t take long for this to become imbued into their daily routine because it was simple and it was effective.

In fact the results were so good that we thought it was probably unethical not to inform the control villages but that was at the end of our study. And as it turned out, the control villages on their own learned about this and started filtering as well. So it was really engaging the women, who in fact were the ones collecting water for their families.

PopTech: The sari water filtration study follows a couple of trends we've been seeing in the field of social entrepreneurship around radical affordability and harnessing ambient infrastructure, literally the clothing on peoples' backs. I'm wondering how these trends inform your approach to your work and if there are other examples that you responded to.


Rita Colwell: We think households can provide themselves with good water that significantly reduces many of the waterborne diseases in a way that's sustainable and doesn't cost anything. It's a matter of education and individual empowerment.

Everybody can afford a sari. The women obviously wear them. And the old ones are used as dust rags. We tested Chinese Poplin, t-shirt material, brand new, elegant saris that were expensive, and rags.

Part of the idea is that it is so inexpensive and so available that you don't question doing it. You don't think, "Do I get food for tonight's dinner by going down to the village bazaar and selling it or do I continue to filter the water?" If what you use to filter you couldn't sell anyway, then it's going to be used.

This interview was edited and condensed.

Rita Colwell

Rita Colwell is Chairman of Canon US Life Sciences, Inc. and Distinguished University Professor both at the University of Maryland at College Park and at Johns Hopkins University Bloomberg School of Public Health. Her interests are focused on global infectious diseases, water, and health, and she is currently developing an international network to address emerging infectious diseases and water issues, including safe drinking water for both the developed and developing world.