Unseen danger

In the annals of efforts to assure that public drinking water is safe, the year 1993 stands out.

In the early spring of that year something got into the water system of Milwaukee, Wisconsin that sickened 400 people, killing more than 70 of them. It was the worst outbreak of water-borne disease in the United States since record-keeping began in 1920.

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The culprit was found to be a contagious intestinal infection called cryptosporidium, a robust pathogen that for most of the 20th century was known mainly to veterinarians for the watery stools that it produced in animals, but now clearly humans were at risk.

This new vulnerability was explained partly by who had died: mostly people with weak immune systems, including people with AIDs or HIV – a new health dilemma at the time. Indeed the population of victims with weak immune systems was wider still thanks in part to recent advances in medicine: the victims included organ transplant recipients and patients whose immune systems had been impaired by chemotherapy.

All these years later cryptosporidium remains a real concern, and not only in the United States; it’s one of the biggest sources of gastrointestinal illness anywhere.

It can’t be knocked out by chlorine, the universal disinfectant, but there have been successes with ozone technology in Milwaukee through the Colorado-based Water Research Foundation.

Still, the pathogen is a mystery and therefore the subject of intense study around the globe. For example, this June, the 7th International Giardia and Cryptosporidium Conference in France.

Part of the problem is that the parasite is hard to detect before it gets into a body and starts doing damage. So a lot of effort is going into spotting it in water systems before it gets to people.

Bottom line: cryptosporidium remains a worry, and detections can put authorities on high alert. A few months ago the parasite was found in the water system of Portland, Oregon, and the city has put a lot of energy into keeping the public up to date on its response.

I can’t close this posting without noting how the threat of crypto eventually found its way beyond the fields of public health and water management to the territory of popular culture. About a dozen years ago an imaginative American video-game maker came up with a damage-doing protagonist from outer space who set foot on our planet. The character’s name: Cryptosporidium-137. The name of the game: “Destroy All Humans.”