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A filter launched in Britain this week could prevent outbreaks of
life-threatening diarrhoea caused by Cryptosporidium, a protozoan
parasite. Developed by Genera Technologies of Cambridge, the filter lets water
companies screen supplies daily for the tiny spores鈥攃alled
oocysts鈥攚hich usually evade detection. British water companies are
required to fit the system before April next year. The filter traps spores in a
disc of polyester foam compressed from 60 to 3 centimetres thick. This creates
pores just the right size to capture oocysts
(Technology, 12 April 1997, p 23).
When the foam is depressurised, the cysts can be washed out, concentrated and
analysed in a custom-built detector.