No, nobody. Touched a duck? Yes, but so what, lots of people did that. Touched a sick chicken? Eaten a guava? Eaten a banana? Eaten an animal that was ill at the time of slaughter? Eaten a star fruit? Touched someone who was feverish, confused, and who later died?
The questions themselves are like pen strokes on a sketch of Bangladeshi village life. But none of those questions—not even the one about tree climbing, this time—yielded any statistically significant distinction between those who had gotten sick and those who hadn’t. Only one question asked by the Luby team did: Have you drunk any raw date-palm sap recently?
Gulp, um, yeah. Date-palm sap is a seasonal delicacy in the villages of western Bangladesh. It flows in the veins of a certain palm tree, the sugar date palm (Phoenix sylvestris), and if the tree is tapped, sap will drain into a carefully placed clay pot. Like the sap of a maple tree, it’s sugary—even more sugary than maple, evidently, because it needn’t be rendered down with hours of cooking. Some people are ready to pay good takas, scarce cash, for date-palm sap offered fresh and raw. Tappers sell it door-to-door in the nearby villages, or else on the roadside, like a neighbor kid with a lemonade stand. Customers usually bring a glass or a jar of their own. They drink it down on the spot or carry it home to share with the family. The best quality sap is red, sweet, and clear. Natural fermentation sets in quickly, and the price plummets after 10 a.m., when the sap is no longer so fresh. Impurities also lower the value. Impurities, as you’ll see, have another result too.
The investigation at Tangail found that single distinction between the sick and the well: Among those infected, most had drunk raw date-palm sap. Their healthy neighbors mostly hadn’t. It suggested a more intricate story.
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So I went to see Steve Luby, at the ICDDR,B. He’s a tall, gaunt man with short brown hair and glasses, serious but not pompous, a former philosophy major who turned to medicine and epidemiology, and then chose to focus on infectious diseases in low-income countries. He has been in Bangladesh since 2004. He knows the place pretty well. He hears a steady tolling of preventable deaths and tries hard to prevent as many as possible. Much of his work involves familiar and mundane diseases, such as pneumonia, tuberculosis, and diarrhea, which cause far greater mortality than Nipah. Bacterial pneumonia, for instance, accounts for about ninety thousand deaths annually just among Bangladeshi children under age five. Bacterial diarrhea kills about twenty thousand newborn infants every year. Given those numbers, I asked Luby, why divert any attention at all to Nipah?
To be prudent, he said. Classic case of the devils you know versus the devil you don’t know, none of which can you afford to ignore. Nipah is important because of what might happen and because we understand little about how it might happen. “This is a horrible pathogen,” he said, reminding me that the lethality among Nipah cases in Bangladesh is more than 70 percent. “Of those who survive, a third of them have marked neurological deficits. This is a bad disease.” And about half of all known cases in Bangladesh, he added, have acquired it by person-to-person transmission, a worrisome development that hadn’t appeared during the Malaysian outbreak of Nipah.
Why has person-to-person spread been a major factor in some of the outbreaks but not others? How stable is the virus? What’s the chance that it might evolve into a form that’s even more readily transmissible? Bangladesh, as I’ve mentioned, is very densely populous, with about a thousand humans per square kilometer, and still increasing. That population, dispersed rather evenly across a crowded but rural landscape, with low levels of income and medical care, pressing relentlessly against the last remnants of native landscape and wildlife, puts the country at special risk of epidemics, whether from old mundane pathogens or strange new ones. So of course Nipah is an important part of our work, Luby said, even though the numbers (so far) are small.
And there’s another reason, he added. No one in the world knows much about this virus. “If we do not study it in Bangladesh, it will not get studied.” Malaysia has seen only one outbreak. India, one in 2001, and another recently. Bangladesh, he pointed out, citing the count as of 2009, has had eight outbreaks in eight years (and more since my conversation