A Quick Reference Guide

Prepared by Tom Neltner on January 17, 2001

This quick reference guide was developed from documents published by the Centers for Disease Control and Prevention as well as the Environmental Protection Agency. For more information, see CDC’s website at http://www.cdc.gov/health/diseases.htm. It is for general information only and not intended to be an authoritative source or to be used as a substitute for consultation with a health care provider.

Key Term:

Pathogen: Organisms capable of eliciting disease symptoms. The identification of mircoorganisms (e.g., bacteria, viruses, or parasites) pathogenic to humans can be difficult. Therefore, the presence of coliforms in water is usually determined as an indicator of the possible presence of fecal-derived pathogens.

Key Parasites:

Giardia lamblia: A one-celled, microscopic parasite that lives in the intestines of people and animals. The parasite is passed in the bowel movement of an infected person or animal. During the past 15 years, Giardia lamblia has become recognized as one of the most common waterborne diseases in humans in the United States. The parasite is found in every region of the United States and throughout the world. Symptoms of Giardia lamblia are diarrhea, abdominal cramps, and nausea. These symptoms typically appear 1 to 2 weeks after infection and can last 4 to 6 weeks. The symptoms can lead to weight loss and dehydration. However, not everyone infected has these symptoms. The parasite is somewhat resistant to chlorine at levels typically found in swimming pools.

Cryptosporidium: Cryptosporidium is an important emerging pathogen in the United States and a cause of severe, life-threatening disease in patients with AIDS and others with damaged immune systems. It is manifested as an acute, self-limiting diarrheal illness lasting 7 to 14 days and it is often accompanied by nausea, abdominal cramps, and low-grade fever. No safe and effective form of specific treatment has been identified to date.

The parasite is transmitted by ingestion of occysts excreted in the feces of infected humans or animals. The infection can result from swallowing just 10 to 100 occysts - a mouthful of contaminated water. The parasite is resistant to chlorine at levels typically found in swimming pools. Sand filtration is not adequate to remove it because the parasite is too small. All waterborne outbreaks detected to date have occurred in communities where water utilities met state and federal standards for acceptable quality of drinking water.

The parasite was the cause of an outbreak in Milwaukee in 1993 that affected over 400,000 persons. There is considerable circumstantial evidence that low-level (non-epidemic) transmission of Cryptosporidium species through drinking water may be occurring throughout the United States. Recent studies indicate that its oocysts are present in 65% to 97% of surface waters tested.

Key Bacteria:

Coliforms: All aerobic and facultative anaerobic, gram-negative, non-sporeforming, rod-shaped bacteria that ferment lactose with gas formation within 48 hours at 95 F.

Total coliforms: Non-fecal and fecal coliforms that are detected with a standard test.

Fecal coliforms: Subgroup of coliform bacteria that has a high correlation with fecal contamination associated with warm-blooded animals. Fecal coliforms are those that grow and produce gas at 112.1 F in 24 hours.

Enteric bacteria: Bacterial species that normally inhabit the intestinal tract of humans and animals. Included in this group of organisms are some of the most important intestinal pathogens of humans. Most enteric bacteria do not cause disease when confined to the intestinal tract of a healthy host, but given a susceptible host or an opportunity to invade other body sites, many have the capability to produce disease in any tissue.

Escherichia coli. (E. coli.): A subset of the coliform group that is part of the normal intestinal flora in humans and animals and is, therefore, a direct indicator of fecal contamination of the water. Most strains are harmless and live in the intestines. However some strains produce a powerful toxin that can cause severe illness.

E. coli. O157:H7: An emerging form of E. coli. that produces a powerful toxin that can cause severe illness. The symptoms are bloody diarrhea and severe abdominal cramps that can last 5 to 10 days. Usually little or no fever is present. In children under 5 years of age and the elderly, the infection can cause a complication called hemolytic uremic syndrome, in which red blood cells are destroyed and the kidneys fail

Shigella: A group of bacteria that cause shigellosis. Most who are infected with Shigella develop diarrhea, fever, and stomach cramps starting a day or two after they are exposed to the bacterium. The diarrhea is often bloody. In some persons, especially young children and the elderly, the diarrhea can be so severe that the patient needs to be hospitalized. A severe infection with high fever may also be associated with seizures in children less than 2 years old. Some persons who are infected may have no symptoms at all, but may still pass the Shigella bacterium to others. Most Shigella bacteria pass from one infected person to the next. It may also be spread by eating contaminated food or by drinking or swimming in contaminated water. Water may be contaminated if sewage runs into it, or if someone with shigellosis swims in it. In 2000, Indianapolis had an outbreak of shigellosis that affected over 1000 people.

Leptospira: A bacteria that affects humans and animals that causes leptospirosis. It takes 2 days to 4 weeks to develop. Symptoms include high fever, severe headache, chills, muscle aches, and vomiting, and may include jaundice, red eyes, abdominal pain, diarrhea, or a rash. In some cases, there may be no symptoms. If the disease is not treated, it can cause kidney damage, meningitis, liver failure, and respiratory distress. Outbreaks of leptospirosis are usually caused by exposure to water contaminated with the urine of infected animals. The animals may be sick and have no symptoms.

Legionella pneumophila: A bacteria that causes Legionnaires’ disease or the milder form called Pontiac fever. Patients with Pontiac fever experience fever and muscle aches and do not have pneumonia. They generally recover in 2 to 5 days without treatment. Outbreaks of legionellosis have occurred after persons have breathed mists that come from a contaminated water source. It is not passed person-to-person. The bacteria reproduce in warm, stagnant water (90 F to 105 F).

Mycobacterium marinum: A bacteria that takes 7 to 14 days to incubate. Symptoms include a lesion most commonly over a bony prominence. The lesion enlarges over a 4 to 8 week period. It is more common in adults than children.

Clostridium perfringens: A species of anaerobic (oxygen intolerant), spore forming bacteria present in the intestinal tract of humans and animals. Since it does not flourish in the tropics, it may be an appropriate indicator to detect possible fecal contamination.

Pseudomonas aeruginosa: Bacterial species found as normal flora in the gut of humans.

Enterococci: Enteric streptococcal (round) bacteria used to indicate fecal contamination and the possible presence of pathogens.

Staphylococcus: Type of bacteria commonly found as normal flora in the gut and other areas.

Hepatitis A: A virus that causes jaundice, abdominal pain, loss of appetite, intermittent nausea and diarrhea. It is primarily transmitted by food or fecal contaminated water. 33% of Americans have evidence of past infection. A highly effective vaccine is available.

Hepatitus E: A virus that can result in abdominal pain, anorexia, dark urine, fever, hepatomegaly, jaundice, malaise, nausea, and vomiting. The symptoms appear after an incubation period that averages 40 days. No vaccine is available.

Adenoviruses: A virus that commonly causes respiratory illness that may also cause gastroenteritis, conjunctivitis, cystitus, and rash illness. Symptoms of respiratory illness range from the common cold syndrome to pneumonia, croup, and bronchitis. Patients with compromised immune systems are especially susceptible to severe complications.

Adenoviruses are unusually stable to chemical and physical agents and adverse pH conditions, allowing for prolonged survival outside the body. They are transmitted by direct contact, fecal-oral transmission, and occasionally waterborne transmission. Outbreaks of adenovirus-associated respiratory disease have been more common in the late winter, spring, and early summer. However, they can occur throughout the year.

Caliciviridae (Norwalk-like virus): An emerging virus first found in fecal specimens collected during an outbreak of gastroenteritis at an elementary school in Norwalk, Ohio. Some outbreaks have been traced back to fecally contaminated foods and water. The majority of calciviridae outbreaks go without a diagnosis because detection methods were not available until recently.

The amount required to cause disease is so small that a little contamination can go a long way, and the virus can pass through simple filters and remain infectious despite routine levels of chlorine.

Rotavirus: The most common cause of severe diarrhea among children, resulting in the hospitalization of approximately 55,000 children each year in the United States and the death of over 600,000 children annually worldwide. The symptoms of the disease are vomiting and watery diarrhea for 3 to 8 days. These symptoms develop after an incubation period of 2 days. Immunity after infections is incomplete, but repeat infections tend to be less severe than the original infection.

The primary mode of transmission is fecal-oral. Because the virus is stable in the environment, transmission can occur through ingestion of contaminated water or food or contact with contaminated surfaces. In the United States, the disease has a winter seasonal pattern, with annual epidemics occurring from November to April.