Our indelicate yet timely subject this issue is Cryptosporidium parvum (C. parvum). "Crypto," as it is often called, is a microscopic parasite that often lives in the intestines of infected animals and humans and released in bowel movements. It is found in soil, food, water and surfaces contaminated with infected feces. Crypto is not spread by contact with blood.

According to the CDC, Crypto can be spread in the following ways:

• By putting something in your mouth or accidentally swallowing something that has come in contact with the stool of a person or animal infected with Crypto

• By swallowing recreational water (swimming pools, hot tubs, Jacuzzis, fountains, lakes, rivers, springs, ponds and streams) contaminated by sewage or feces from humans or animals infected with Crypto

• By eating uncooked food contaminated with Crypto

• By accidentally swallowing Crypto picked up from surfaces such as toys, bathroom fixtures, changing tables or diaper pails contaminated with stool from an infected person

What Are the Symptoms of Crypto?

The symptoms of Crypto include diarrhea, loose or watery stool, stomach cramps, nausea and a slight fever. Some people are asymptomatic. Symptoms generally manifest in two to ten days after infection. In healthy persons with average immune systems, symptoms usually last about two weeks and may go in cycles, during which time one may seem to improve for a few days, then feel worse before symptoms abate.

How Does Crypto Affect the Immunosuppressed?

According to the CDC, "In persons with AIDS and in those whose immune system is weakened, Crypto can be serious, long-lasting and sometimes fatal. If your CD4 cell count is below 200, Crypto is more likely to cause diarrhea and other symptoms for a long time. If your CD4 count is above 200, your illness may not last more than one to three weeks or slightly longer. However, you could still carry the infection, which means that the Crypto parasites are living in your intestine, but are not causing illness. As a carrier of Crypto, you could infect other people. If your CD4 count later drops below 200, your symptoms may reappear."

How Is Crypto Diagnosed and Treated?

Your health care provider will ask you to submit stool samples over several days. There is no effective treatment for Crypto at this time. If you have diarrhea, drink plenty of fluids to prevent dehydration, which can be life-threatening, especially in infants. Persons living with HIV are at a higher risk for more prolonged and severe symptoms. Those persons on antiretroviral therapy that improves immune function will also decrease or clear symptoms of Crypto. However, should the immune system decline, symptoms may return.

How to Avoid Becoming Infected (CDC Recommendations)

1. Wash your hands.
Washing your hands often with soap and water is probably the single most important step you can take to prevent Crypto and other illnesses. Always wash your hands before eating and preparing food. Wash your hands well after touching children in diapers; after touching clothing, bedding, toilets or bed pans soiled by someone who has diarrhea; after gardening; any time you touch pets or other animals; and after touching anything that might have had contact with even the smallest amounts of human or animal stool, including dirt in your garden and other places. Even if you wear gloves when you do these activities, you should still wash well when you finish. Children should be supervised by adults to make sure they wash their hands well.

2. Practice safer sex.
Infected people may have Crypto on their skin in the anal and genital areas, including the thighs and buttocks. However, since you cannot tell if someone has Crypto, you may want to take these precautions with any sex partner. "Rimming," "tossing salad" or "cleaning the kitchen" (slag terms for kissing or licking the anus) is so likely to spread infection that you should avoid it, even if you and your partner wash well beforehand. Always wash your hands well after touching your partner's anus or rectal area. Barrier protection is advised if coming in contact with the anus.

3. Avoid touching farm animals.
If you touch a farm animal, particularly a calf, lamb or other young animal, or visit a farm where animals are raised, wash your hands well with soap and water before preparing food or putting anything in your mouth. Do not touch the stool of any animal. After you visit a farm or other area with animals, have someone who is not immuno-compromised clean your shoes, or wear disposable gloves if you clean them yourself. Wash your hands after taking off the gloves.

4. Avoid touching the stool of pets.
Most pets are safe to own. However, someone who is not immuno-compromised should clean their litter boxes or cages and dispose of the stool. If you must clean up after a pet, use disposable gloves and wash your hands afterwards. The risk of getting Crypto is greatest from pets that are less than six months old, animals that have diarrhea and stray animals. Older animals can also have Crypto, but they are less likely to have it than younger animals. If you get a puppy or kitten that is less than six months old, have the animal tested for Crypto before bringing it home. If any pet gets diarrhea, have it tested for Crypto.

5. Avoid swallowing water when swimming in the ocean, lakes, rivers or pools, and when using hot tubs.
When swimming in lakes, rivers or pools, and when using hot tubs, avoid swallowing water. Several outbreaks of Crypto have been traced to swallowing contaminated water while swimming. Crypto can live in chlorinated swimming pools and water parks for days. Crypto also can remain alive in salt water for several days, so swimming in polluted ocean water may also be unsafe.

6. Wash and/or cook your food.
Fresh vegetables and fruits may be contaminated with Crypto. Therefore, wash well all vegetables or fruit you will eat uncooked. If you can, take extra steps to make your water safe and use this safe water to wash your fruits and vegetables. When you can, peel fruit that you will eat raw after washing it. Do not eat or drink unpasteurized milk or dairy products. Cooking kills Crypto. Therefore, cooked food and heat-processed foods are probably safe if, after cooking or processing, they are not handled by someone infected with Crypto or exposed to possibly contaminated water.

7. Drink safe water.
Do not drink water directly from lakes, rivers, streams or springs. Because you cannot be sure if your tap water contains Crypto, you may wish to avoid drinking tap water, including water or ice from a refrigerator, which is usually made with tap water. Because public water quality and treatment vary throughout the United States, always check with the local health department and water utility to see if they have issued any special notices about the use of tap water by immuno-compromised persons. You may also wish to take some additional measures: boiling your water, filtering your water with certain home filters or drinking certain types of bottled water. Processed carbonated (bubbly) drinks in cans or bottles are probably safe, but drinks made at a fountain might not be because they are made with tap water. If you choose to take these extra measures, use them all the time, not just at home. If the public health department advises boiling the water, do not drink tap water unless you boil it. You could also use one of the bottled waters described below:

• Boiling water: Boiling is the best extra measure to ensure that your water is free of Crypto and other germs. Heating water at a rolling boil for one minute kills Crypto, according to CDC and EPA scientists. After the boiled water cools, put it in a clean bottle or pitcher with a lid and store it in the refrigerator. Use the water for drinking, cooking or making ice. Water bottles and ice trays should be cleaned with soap and water before use. Do not touch the inside of them after cleaning. If you can, clean water bottles and ice trays yourself.

• Filtering tap water: Not all available home water filters remove Crypto. All filters that have the words "reverse osmosis" on the label protect against Crypto. Some other types also work, but not all filters that are supposed to remove objects one micron or larger from water are the same. Look for the words "absolute one micron." Some "one micron" and most "nominal one micron" filters will not work against Crypto. Also look for the words "Standard 53" and the words "cyst reduction" or "cyst removal" for an NSF-tested filter that works against Crypto.

To find out if a particular filter removes Crypto, contact NSF International [3475 Plymouth Road, PO Box 130140, Ann Arbor MI 48113-0140; phone (800) 673-8010], an independent testing group. Ask NSF for a list of "Standard 53 Cyst Filters." Check the model number on the filter you intend to buy to make sure it is exactly the same as the number on the NSF list. Look for the NSF trademark on filters, but be aware that NSF tests filters for many different things. Because NSF testing is expensive, many filters that may work against Crypto have not been tested. Reverse-osmosis filters work against Crypto whether they have been tested by NSF or not. Many other filters not tested by NSF also work if they have an absolute pore size of one micron or smaller.

With all that said, let's be realistic. Yes, if you have $1,200, go buy the newest refrigerator with a water filter for the ice and water dispenser. If not, spend about $50 on a faucet-mounted water filter that purifies about 100 gallons. After the initial investment, the filters cost about $17 each and this comes to about 17¢ per gallon -- a lot cheaper than bottled water.

Also, be careful when cleaning up after your pet, which does not mean you have to get rid of your favorite four-legged friend. When swimming this summer, avoid polluted lakes and rivers (stay in the boat), swim in clean swimming pools and soak in clean spas.

Quality of life issues come in to play here as well, and the key is moderation and common sense. Have a fun and safe summer and don't forget the sunscreen, a fun hat and the filtered water!