Clear Solution

What If You Developed a Way to Save Thousands of Lives—and No One Was Interested?
by Chris Carroll | photo illustration by Kelsey Marotta ’14

In a small, impoverished village south of the Bangladeshi capital of Dhaka, a woman was lugging a heavy jug of water home from a nearby pond when two UMD researchers, Rita Colwell and Anwar Huq, stopped her for a quick demonstration.

First they poured a bit of the water into a clear glass beaker; then they filled a second beaker with water they filtered for her on the spot.

The filter they’d come to Bangladesh to test was no high-tech piece of gear from a science lab or an expensive outfitter. Instead they used a thin, folded scrap of cloth cut from an old sari, a colorful traditional garment women wear throughout South Asia. They showed her the two beakers of pond water—one clear, one green and murky.

“She immediately poured all that water out on the ground in front of us,” says Huq, a professor in the Maryland Pathogen Research Institute. “Then she went home, got some sari cloth and went to refill.”

The technique was an easy sell to the woman, who immediately grasped that cleaner water could improve her family’s health. Her intuition was borne out by research Colwell and Huq published in 2003 proving sari cloth doesn’t just make water look better—it saves lives by cutting the incidence of the infectious disease cholera in half.

And yet more than a decade later, the three-year field study they carried out remains the only time the technique was ever implemented.

Governments, foundations and global health agencies have lauded sari cloth filtering for its brilliant simplicity and effectiveness, but they’ve passed on actually using it.

No one is questioning the scientific basis of the technique. The wild card many authorities doubt is people—villagers like the woman carrying pond water. Would she continue filtering without researchers present? Would she follow the procedure incorrectly and endanger her family?

Such questions are reasonable, given limited resources and the need to focus only on the best interventions, says Dr. David Sack, one of the 2003 study’s co-authors.

“Can you teach it to people, and will they follow it?” says Sack, a cholera expert and professor at Johns Hopkins University’s Bloomberg School of Public Health. “Anytime you have an intervention based on changing people’s behavior, it’s not easy. With cholera, you have to teach 1 billion people” who lack access to safe water.


Vibrio cholerae is a singularly nasty breed of bacteria. The immune system copes with low doses, but if enough get into the body, typically via polluted water, they overwhelm cells lining the intestinal tract. The bacteria release a toxin with the sole, deadly effect of sucking water from the body and expelling it as a whitish fluid in a torrent of vomit and diarrhea that spreads the disease. Cholera infects untold millions, and through dehydration kills an estimated 120,000 yearly, according to the World Health Organization (WHO).

The two UMD researchers, specialists in environmental microbiology and molecular microbial ecology, have devoted much of their careers to tracking it. Colwell described the ecology of Vibrio bacteria in the Chesapeake Bay and elsewhere as early as the 1960s in her Ph.D. thesis. She later developed a widely hailed method to predict cholera outbreaks using satellite imagery. Huq ph.d. ’84, a former student of Colwell’s and a native of Bangladesh, discovered that Vibrio cholerae attaches in droves to plankton called copepods.

Since publication of the 2003 sari paper, other means of fighting cholera globally have predominated, including vaccines, chemical water purification, even better nutrition. All are crucial, say Huq and Colwell, who support a multipronged approach.

But one thing sets their sari cloth method apart: People without access to more sophisticated methods need little more than simple information to use it.

Colwell and Huq still have plans, if not funding, to apply the technique. New funding proposals are in the works to teach the technique in remote Bangladeshi villages, and Huq has tested cloth samples from Africa, hoping to introduce the method in areas of the continent that lack treated water.

Utter simplicity is the goal, so people enduring grinding poverty or the aftermath of earthquakes or floods have a fighting chance to protect themselves. Perhaps that works against it in our technophilic world, says Colwell, a distinguished university professor both at UMD and Johns Hopkins University.

“It doesn’t have complicated chemistry or sophisticated technology,” she says. “And maybe those who haven’t worked in remote villages suffering extreme poverty never understood what we were trying to address.”


In the 1990s, seeking a way to put decades of research to work in the real world, Colwell and Huq settled on the idea of an ad hoc filter from readily available material. Their lab tests, funded by the Thrasher Research Fund, showed that cotton sari cloth, fuzzy from repeated washings, worked as well as some commercial filter membranes, removing 99 percent of cholera bacteria from water.

A branch of the National Institutes of Health that deals with infectious diseases declined to fund a large-scale field trial—perhaps believing the method too elementary, Colwell says.

But it was anything but a spur-of-the-moment wild idea.

“This evolved from many years of research,” she says. “The larger context is 700 or 800 publications on vibrios and disease outbreaks.”

Finally in 1999, with funding from the National Institute of Nursing Research, they began a massive field study involving 45,000 people in 65 villages in southern Bangladesh. Researchers trained women as extension agents who fanned out to teach a relatively simple technique:

Sari cloth is folded into four layers, then placed over the mouth of a kalash, a water jug used in villages. Water is poured in, then the cloth is removed, rinsed with filtered water and hung to dry. Air and sunlight disinfect it for the next use.

The experiment yielded dramatic results, published in 2003 in Proceedings of the National Academy of Sciences. The researchers documented a 48 percent reduction in cholera in villages that practiced sari filtration, compared to villages that didn’t. Although the trial was carefully designed to focus on cholera and didn’t address other intestinal pathogens, experts say the technique likely prevented a range of illnesses.


The result—roughly on par with cholera vaccines, which have cost billions to develop and test—was widely reported in the media and scientific circles, and lauded by leading cholera experts.

And yet doubts were rising. Several epidemiologists questioned whether that rate of success was sustainable, or if villagers would disregard the method without constant reinforcement.

Some advocates of vaccines for cholera, meanwhile, seemed to think Colwell and Huq were pushing sari cloth as an alternative—which they weren’t. It’s a last-ditch option for millions without access to vaccines or advanced interventions, Colwell says.

“We never, never intended it as a substitute for vaccines,” she says. “Ideally, these approaches could be used together. But villagers who lack access to vaccination need something to protect themselves against this potentially deadly disease.”

Global applicability is another issue. Batsi Majuru of WHO says sari filtration clearly works well at stopping waterborne cholera in Bangladesh, but wasn’t tested elsewhere, including places where cholera isn’t associated with plankton or other tiny marine organisms.

Perhaps more importantly, says Majuru, a technical officer for WHO’s Water, Sanitation, Hygiene and Health unit, the agency backs interventions that are proven useful in tests against a range of disease agents.

“At a minimum, it needs to be effective against two pathogen classes—bacteria, viruses and protozoa,” she says.

To date, the sari filter’s only documented effect has been to eliminate cholera bacteria in water.


In 2010, a follow-up study showed that five years after researchers left them on their own, 31 percent of Bangladeshi villagers in the study group still filtered water and that the practice still prevented cholera. Interestingly, the practice had spread to some villages where sari filtering was never taught.

For Huq and Colwell, it was a promising result that showed a significant portion of study participants followed the routine without guidance.

A national media campaign utilizing radios and posters could quickly spread knowledge of the technique to remote areas without clean water, proving the technique’s sustainability, Huq insists.

To Andrew Camilli, a cholera expert and professor of micro- and molecular biology at Tufts University, the follow-up study had a “glass half-full, glass half-empty” result.

But even if the sari method is less than perfect, he says, it could have saved many lives over the past decade. It’s difficult to understand the collective yawn the method has met with.

“Any health care worker going into the villages doing physicals or vaccinations from who or wherever—they should be training people to do this,” he says. “We know it works.” TERP


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