Sometimes the answer to a health mystery lies in a swig of booze.
In Bangladesh in recent years, there have been repeated mini-outbreaks of a disease called Nipah virus – three people here, four there.
Some people develop no symptoms. But in others, the virus can progress from a fever to fatal brain inflammation within a week.
A few years ago, epidemiologists figured out that people were likely getting Nipah from drinking raw date palm sap, a sweet drink popular in the winter, when the sap is easy to tap from trees pierced with a spigot.