What is the most common cause of waterborne disease and Where does Cryptosporidium come from?

On September 3, 1999, 10 children in counties near Albany, New York, were hospitalized with bloody diarrhea, and everyone wanted to know why.

Health officials quickly discovered two facts: they were all infected with E. coli O157:H7, the most deadly form of the E. coli bacterium, and they had all attended the Washington County Fair, held two weeks earlier.

By September 15, more than 900 fair attendees had reported diarrhea, and examination of stool cultures revealed that 116 of them were infected with E. coli O157:H7. Sixty-five people were hospitalized and 11 children had developed hemolytic uremic syndrome (HUS), a disorder that damages blood cells by causing waste products to accumulate in the blood instead of being excreted in the urine.

Two people, a three-year-old girl and a 79-year-old man, both of whom had HUS, were dead. Finally, an environmental study of the fairgrounds uncovered the truth: most of the water at the fair was chlorinated and perfectly safe for drinking, but one area where several food vendors used water to make drinks and ice was supplied by a well. The well water was highly polluted with E. coli, and careful testing showed that the strain was O157:H7.

Stories like this may make you want to buy bottled water and a water filtration system, and in fact those are two growth industries in the United States. Americans spend nearly $6 billion a year on bottled water, and it’s no wonder, considering the way restaurants, convenience stores, and soda vending machines are pushing the stuff.

But carrying a little plastic bottle of water, preferably one with a foreign name written on it, is more a fashion statement than a physiological necessity. The fact is that most municipal water systems in this country, and most wells, are perfectly safe, just as safe as a bottle of Perrier. But every once in a while things seem to fall apart, as they did in Milwaukee in 1993, when the failure of the purification system there caused an outbreak of cryptosporidiosis that left 400,000 people sick and 100 dead, but more about cryptosporidiosis in a moment.

When you look at the list of pathogens that have turned up in water supplies over the past few years, giardia, salmonella, campylobacter, yersinia, Entamoeba histolytica, E. coli, shigella, cryptosporidium, it’s enough to make you reach for bottled water even if you just want to brush your teeth. And we haven’t even gotten around to the presence of lead, arsenic, chloroform, pesticides, and radioactive waste in your drinking water, things a little off our main subject here, but which, as you might imagine, come with their very own horror stories. But let’s not panic about pathogens just yet. The tale of the turbid water in Washington, D.C., is instructive.

On December 6, 1993, the District of Columbia began to have difficulties with their filtration system, and levels of turbidity (that is, suspended particles in the water) rose above levels allowed by Environmental Protection Agency standards. Turbidity can be caused by many different pollutants, including some things that are completely harmless. But it’s aesthetically undesirable, the solids may contain something harmful, and it can decrease the effectiveness of water treatment techniques by protecting pathogens from chemical or thermal damage. D.C. water is chlorinated, and throughout the period of the failing filtration, chlorination remained normal. Chlorine kills many different waterborne organisms, but there is at least one that it doesn’t kill: cryptosporidium, a common cause of intestinal disease.

Cryptosporidium is a protozoan parasite discovered in 1976, and it exists all over the world. Along with Giardia lamblia, another protozoan, it is the most common cause of waterborne disease in the United States. There are many different species that infect animals, but only one, called Cryptosporidium parvum, infects humans.

The organism has a complex life cycle, including sexual and asexual reproductive stages, and exists in large quantities in human stool. You get it by ingestion, that is, by getting stool into your mouth. Crypto, as it is called for short, can survive for several days in water, and if you swallow enough of that water, you get a stomachache, bad diarrhea, and sometimes a fever. The unpleasant symptoms can last for quite a while, up to two weeks, and they usually begin between 2 and 10 days after you’re exposed to the parasite. You can die from this infection, as some did in the Milwaukee case, but almost all deaths are among the very old, the very young, and the immunocompromised. In fact, many people may have cryptosporidium in their stool without experiencing any symptoms at all.

In any case, the authorities in Washington were concerned that crypto might be one of the things suspended in the water. The water was eight times more turbid than the water in Milwaukee that made 400,000 people ill, that is, eight times as many particles were suspended in it. But the tests to determine the actual presence of crypto in water are both expensive and highly inaccurate, so most water companies don’t use them. DC was luckier than Milwaukee.

Apparently, whatever was causing the turbidity in the water in Washington wasn’t causing cryptosporidiosis, because reports of diarrheal illness were no higher after the filtration problems started than they were before. The water didn’t look very good, and it certainly frightened lots of people, including those in charge of the water system, but in the end, unlike the Milwaukee case, it probably didn’t do much harm.

Cryptosporidium parasites are large enough that they can be filtered out of drinking water, and most municipal water systems, like those in Milwaukee and Washington, D.C., when they’re working right, do just that. But if you have reason not to trust the municipal system, you can buy your own filter and attach it to your tap or have it installed on the pipes leading to the tap.

There are lots of home water filters sold, but not all of them will work to catch cryptosporidium before it winds up in your drinking glass. To find out if a particular filter removes crypto, you can contact NSF International, a nonprofit organization that does voluntary testing of many products (3475 Plymouth Road, P.O. Box 130140, Ann Arbor, MI 48113-0140, 800-673-8010).

Any filter that NSF has tested and that works against crypto will have the words “Standard 53” and “cyst reduction” or “cyst removal” on the label. NSF testing is paid for by the product manufacturer, and since it is expensive, not all manufacturers want to acquire this seal of approval. This doesn’t in itself mean that the filter will not be effective against crypto, however. There are four phrases you can look for that are sure indications that the filter will work:

• Reverse osmosis (with or without NSF testing)
• Absolute pore size of 1 micron or smaller (with or without NSF testing)
• Tested and certified by NSF Standard 53 for cyst removal
• Tested and certified by NSF Standard 53 for cyst reduction

There are lots of other descriptions that can appear on water filter labels, but none except those above assures you that crypto will be filtered out. Filters that have wording like the following on them may or may not work:

• Nominal pore size of 1 micron or smaller
• One micron filter
• Effective against Giardia
• Effective against parasites
• Carbon filter or activated carbon
• Water purifier
• EPA approved or EPA registered (this is particularly deceptive, since the Environmental Protection Agency doesn’t test, approve, or register water filters)
• Removes chlorine
• Ultraviolet light
• Pentiodide resins
• Water softener

Changing filter cartridges at the recommended intervals is essential, and anyone who changes the cartridge should wear gloves and wash his hands thoroughly after handling the old filter.

What about other drinks? Can they contain crypto? Maybe. In general, canned or bottled soda, seltzer, and fruit drinks are free of cryptosporidium thanks to the manufacturing and canning process, but fountain drinks, iced tea and coffee, and concentrated juice that you mix with tap water may not be.

You may decide that bottled water is the way to go, but even here, you have to be careful. The water may be in a neat little bottle, but that doesn’t mean that it has been effectively treated to eliminate crypto. Again, there are a few phrases you can look for that will assure that an effective method has been used:

• Reverse osmosis treated
• Distilled
• Filtered through an absolute 1 micron or smaller filter
• One micron absolute

Other phrases don’t mean much when it comes to cryptosporidium. If you see any of the following on the label of a bottle of water, you can’t be sure that crypto has been eliminated:

• Filtered
• Carbon-filtered, particle-filtered, multimedia-filtered
• Ozonated or Ozone-treated
• Ultraviolet-light treated
• Activated carbon treated
• Carbon dioxide treated
• Ion exchange treated
• Deionized
• Purified
• Chlorinated