J. Mac Crawford, Assistant Professor, Division of Environmental Health Sciences, School of Public Health
Karen Mancl, Professor and Water Quality Specialist, Food, Agricultural and Biological Engineering
Water is perhaps the most critical and precious resource that people rely upon. Often taken for granted, clean water just appears when the spigot is opened, the tap is turned on, or the bottle is opened. Well, water is not free. Citizens pay for clean water whether it comes from municipal supplies or bottles. Those who have wells need to be vigilant in making sure the groundwater remains clean—free of bacteria, viruses, and potentially harmful chemicals. According to the World Health Organization (WHO, 2004) about 1.8 million people around the world die from diarrheal diseases each year, and about 88 percent of those deaths are due to unsafe water, and poor sanitation and hygiene. Children account for the biggest share of that burden. Those are sobering figures, however, the numbers from the United States are much less alarming. During the years 2001 and 2002, the number of waterborne disease outbreaks in the United States decreased to 31 from the 39 reported in the previous two-year period. Those 31 outbreaks caused illness in 1,020 people and resulted in seven deaths (Blackburn et al., 2004).
Few of those alive today remember the conditions under which most people lived prior to modern water treatment methods. It was not uncommon for very severe gastrointestinal disorders (cholera, for example) to ravage large population centers. One famous cholera outbreak occurred in London, England, in the middle of the 19th century. Dr. John Snow had been researching cholera outbreaks for a number of years and he was able to solve this particular outbreak with a rather pragmatic approach. The map in this fact sheet shows central London and includes designations of deaths from cholera, locations of water pumps, and various important landmarks.
Notice the clustering of deaths around “Pump A” on the map. This was also referred to as the Broad Street pump and appeared to be the epicenter of a great many deaths. Look at the two city blocks directly east and then south from the Broad Street pump—there are no deaths in those (and a few other) blocks. There was a brewery operating on those blocks at which workers drank beer for their fluid intake (the brewing process destroys pathogens). This was exactly what Snow had predicted would be a protective benefit of beer drinking—he had observed brewery workers’ lower rates of cholera previously. (Beer drinking is not, however, the currently recommended action to avoid waterborne diseases!)
There were cases from sites near other pumps, but they were comparatively rare, numbering only 10 (out of over 600 total deaths), near one pump. It was later determined that five of those 10 victims regularly drank from Pump A. There were other cases that didn’t seem to fit the pattern, one of which was a woman who liked the taste of the water from Pump A so much that she sent a servant there to bring back a bottle of water every day. The ultimate source of the epidemic appears to be the diaper of a child, living at 40 Broad Street, who became ill with the symptoms of cholera. The diaper had been soaked in water that was then poured into an unsound, leaking cesspool only three feet from the Broad Street Pump (Summers, 1989).
Typically, people think of waterborne illnesses arising from exposure to microbiological agents. These agents do commonly cause disease, but it is important to keep in mind that chemicals can cause illness and that some intestinal maladies may not be traceable to any particular agent. In general, waterborne illness may be classified as Acute Gastrointestinal Illness of unknown etiology (AGI); chemical contamination; and viral, parasitic, and bacterial illness.
Gunther Craun and colleagues (2003) have written extensively about waterborne illness and have summarized information from 230 waterborne disease outbreaks reported between 1991 and 1998. The authors estimate that there were at least 443,000 cases of disease among the inhabitants of 41 states and three U.S. territories. These cases resulted in the hospitalization of 764 people and the deaths of 60 others. The reader should be aware that about 403,000 of the 443,000 cases and 50 out of the 60 deaths reported above were associated with the Milwaukee cryptosporidiosis outbreak in 1993. This outbreak was the largest since the advent of keeping statistics on these outbreaks in 1920. The Milwaukee outbreak, which affected only a part of the city, and was caused by a malfunction at a water treatment plant that was fixed within minutes, shows how these diseases can infect people rapidly and in many geographic regions. Travel, especially to major cities and internationally contributes to the spread. The following paragraphs provide some detail on the kinds of agents that can cause waterborne disease.
Many waterborne disease outbreaks are classified as “unknown.” This is not a very helpful classification because little can be done in the way of prevention or abatement. The fact remains that in many instances there is no clear evidence of what caused the illness. Samples of water taken from a suspected source may test negative because the sampling technique failed to capture an organism or chemical. This can occur because water systems are dynamic—always changing. Conditions, currents, and water quality may be markedly different after a very short time lapse. Modern techniques in molecular biology are making it more feasible to trace agents to their sources, but the techniques are new and constantly evolving.
Chemical agents account for a sizable proportion of outbreaks, approaching 30 percent in community water systems. Craun et al. (2003) indicate that most chemical outbreaks are due to contamination of the distribution system, citing copper (when water is corrosive); and nitrate, soap, and fluoride from backflows. The authors also cite improper addition of chemicals meant to improve health, such as fluoride, sodium hydroxide, and chlorine. Nitrates are sometimes found to be elevated in the spring when rain runoff from farm fields flushes nitrogen-based fertilizers into ground and surface water. Boiling the water is not a solution. Some community members, upon hearing of warnings not to use this water for infants and small children, will boil the water thinking this will “kill” whatever harmful agent is in the water. Unfortunately, this just concentrates the nitrate, making it potentially lethal. Distinguishing between biological and chemical agents is crucial.
Other chemical agents of potential concern include lead from home plumbing, chlorination byproducts like trihalomethanes that result when chlorine used for disinfection binds to carbon to form potentially carcinogenic compounds, pesticides like the herbicide Atrazine, bad-tasting and smelling compounds like hydrogen sulfide (rotten egg odor), and salts from roadway de-icing and home water softening.
Hepatitis A is a virus that has infected relatively few people in the United States in recent history. From the years 1999 through 2003, in Ohio there were 331 cases on average reported per year (Ohio Department of Health, 2005). The virus is transmitted by contaminated water and the fecal-oral route, often when food workers’ hygienic practices are less than optimal (i.e., when they don’t wash their hands thoroughly after using the rest room). A notable outbreak of Hepatitis A occurred in the Pittsburgh area in 2003, infecting at least 660 people from green onions imported from Mexico and served in a Mexican restaurant. Hepatitis A outbreaks from the same source also occurred in Georgia, North Carolina, and Tennessee, infecting over 300 people. While rarely fatal, four victims in Pennsylvania died from this outbreak. The virus can be imparted to food products through irrigation and watering with contaminated water supplies, and in this instance was probably a result of irrigating the onion crop with untreated sewage water.
Symptoms may include (CDC, 2005a):
Noroviruses are named for an outbreak that occurred in Norwalk, Ohio, in 1972. It has since been found to share some features with other viruses now referred to as Norwalk-like and are classified as members of the calicivirus family. Outbreaks in the United States are often associated with eating raw shellfish, especially oysters and clams. Shellfish become contaminated via stool from sick food handlers or from raw sewage dumped overboard by recreational and/or commercial boaters. Contaminated water, ice, eggs, salad ingredients, and ready-to-eat foods are other sources of infection. Shellfish may be an issue in coastal areas, but in the interior, it is mostly salads, baked goods, etc., due to dirty hands that can be a source of infection. Foods eaten raw or handled AFTER cooking get contaminated from food handlers who are working while ill or who were recently ill, and practice poor personal hygiene after using the rest room. Possibly, produce may arrive already contaminated. If it doesn’t get washed well or doesn’t get cooked, the virus may survive, and then is consumed. Waterborne Noroviruses are occasionally recognized. Food-borne and person-to-person are much more common sources.
Symptoms may include (CDC, 2005b):
Giardia lamblia is a one-celled agent that is commonly found in rivers and streams, but may also be found in conventional sources of drinking water. The agent enters the environment from the feces of infected animals or other people. The organism lives in the intestine, but because it has a protective shell, it can survive for long periods of time outside the body. Infections may occur through accidental ingestion of the agent when it is in food, soil, or water. Symptoms may take one to two weeks to appear after infection and may persist for two to six weeks.
Symptoms may include (CDC, 2004a):
Cryptopsoridium is a microscopic parasite that lives in the intestines of its hosts. It is protected by a hard outer shell that provides it some protection from chemical water treatment systems and allows it to live outside the body for extended periods. It may be found in recreational and drinking water almost anywhere in the United States. Cryptopsoridium may be found in soil, food, water, or any surface that has come into contact with either human or animal feces infected with it.
Most commonly, sufferers experience watery diarrhea (CDC, 2005c). Other symptoms include:
Cyclosporiasis has been observed only since 1979. It is a one-celled parasite that may be spread by ingesting contaminated food or water contaminated with feces. One possible way the infection is spread is through contaminated fresh fruit and vegetables that have been handled improperly or washed with contaminated water. Person-to-person transmission is unlikely. Recent outbreaks have included cases resulting from consumption of contaminated raspberries imported from Guatemala. While the precise mechanism of contamination is unknown, Nelson (2004) states, “… it is likely that rinsing of the implicated raspberries with contaminated water prior to their export had occurred.”
Symptoms, if they appear, may last a week or more to a month and may include (CDC, 2004b):
Escherichia coli is a very common bacterium that exists in many varieties. Harmless varieties live in human (and animal) large intestines and are essential to normal digestion. Some types are harmful (E. coli O157:H7), producing a potentially fatal toxin when ingested through contaminated food or water. One well-publicized outbreak in 1993 involved contaminated hamburgers sold through a popular western food chain. It was later determined that the hamburgers had not been cooked to 155 degrees Farenheit, the temperature which effectively kills E. coli that often are found in ground beef. Person-to-person transmission may occur and it may be spread through drinking raw milk or drinking or swimming in contaminated water.
Symptoms, if they appear, include (CDC, 2004c):
Salmonella is a bacterium that is most commonly associated with eating undercooked meat, poultry, and eggs, but can affect water supplies. It can be acquired directly from animals (not just reptiles). It can be spread by food workers who have not practiced good hygiene or through washing fruits and vegetables in contaminated water. Failure to properly wash plates and utensils used to prepare meats and poultry may also cause infection. Salmonella is also commonly associated with reptiles. The illness is usually uncomfortable but not dangerous, except for young children, the elderly, and the immuno-compromised, who may become dangerously dehydrated. Onset of symptoms begins within 12 to 72 hours of infection and illness may last five to seven days. Laboratory testing to establish correct antibiotic treatment may be necessary. Many cases of salmonellosis probably go undetected.
Symptoms include (CDC, 2004d):
Campylobacter is a spiral-shaped bacterium that is spread and causes illness in a manner very similar to salmonella—it is commonly associated with poultry and can be contracted by improper cooking and handling of food and improper washing of dishes, utensils, and cutting boards. It can also be acquired directly from animals. Contaminated water and raw milk are also potential culprits. It is one of the most common bacterial causes of diarrheal illness in the United States. Onset of symptoms begins within two to five days of exposure and typically last a week to 10 days. Treatment including antibiotics is usually unnecessary, but some victims suffer serious, long-term complications, including arthritis and Guillain-Barré syndrome. Guillain-Barré is a condition in which gradually progressive paralysis overtakes the subject, but the paralysis usually reverses. It is estimated that one in 1,000 cases of Campylobacter infection will result in Guillain-Barré and that 40 percent of Guillain-Barré cases are associated with Campylobacter.
Symptoms include (CDC, 2004e):
Shigella is a family of bacteria that causes illness very similar to salmonella and campylobacter, but is usually spreads differently—through the fecal-oral route, facilitated by improper hand washing. Most of the types of Shigella found in the United States cause an uncomfortable illness that is not dangerous, but in the developing world Shigella dysenteriae type 1 causes deadly epidemics. As with several other bacterial infections, Shigella may necessitate hospitalization of the very young or elderly because of profound diarrhea. Some infected individuals show no symptoms but easily pass the illness on to others. Onset of symptoms begins within one or two days after exposure and usually last five to seven days. Treatment with antibiotics is usually done, but antibiotic-resistant strains of Shigella have evolved. About 3 percent of victims of Shigella flexneri suffer a serious, long-term complication known as Reiter’s syndrome, which causes painful joints, irritation of the eyes, painful urination, and perhaps long-term arthritis. The syndrome may last months or years.
Symptoms include (CDC, 2005d):
Vibrio cholerae, causative agent of cholera (see discussion of John Snow above) has been almost completely eliminated from the United States for the past 100 years or so. The United States has been spared except for imported cases, or clusters of infections from imported food. During 1993 and 1994, 69 cholera cases were reported to CDC, and 65 were associated with foreign travel (Todar, 2002). There was a major outbreak in 1991 in South America that affected several countries, as well as an outbreak in Bangladesh in 1992. Despite the history of serious illness and death associated with cholera, illness may be mild or asymptomatic, but in severe cases dehydration and shock may lead to death within hours without treatment. The organism is usually spread by eating contaminated seafood (usually shellfish) and drinking contaminated water. Antibiotics may shorten the duration of illness but re-hydration is critical to reducing the chance of death.
Symptoms include (CDC, 2004f):
More disease-causing agents than these exist, mainly affecting people in developing nations. Many medical scientists have recently thought infectious diseases had been conquered by the advent of antibiotics. What they failed to recognize was that bacteria develop resistance to antibiotics, and viruses can mutate in such a way as to render vaccines ineffective. In addition to these forces, modern travel has enabled microbes that normally were confined to remote, isolated populations to spread beyond their normal habitats. It behooves us to exercise care in choosing drinking water sources, particularly when traveling, and to invest resources at home to assure safe municipal water supplies.
There are several ways to treat water that is of questionable microbial quality (CDC, 2005e): boiling, chemical treatment, and filtering. Water should be boiled vigorously for 1 minute and allowed to cool naturally (don’t add ice). At elevations above 6,500 feet, boil for 3 minutes (water boils at lower temperatures as atmospheric pressure drops with altitude). Chemical disinfection may be done with iodine-based products available in sporting goods stores, but certain parasites such as Cryptosporidium, Cyclospora, and Toxoplasma, may not be killed. Portable filters are available commercially and will effectively remove parasites; however, they are ineffective against viruses, which are orders of magnitude smaller than parasites and bacteria. Another alternative is to drink bottled water. At home, make sure the septic system is working properly without any surface discharge. And, finally, always wash your hands!
Blackburn, B.G., Craun, G.F., Yoder, J.S., Hill, V., Calderon, R.L., Chen, N., et al. Surveillance for Waterborne-Disease Outbreaks Associated with Drinking Water—United States, 2001–2002. Morbidity and Mortality Weekly Report, October 22, 2004/53(SS08); 23–45.
CDC. 2004a. www.cdc.gov/ncidod/dpd/parasites/giardiasis/2004_PDF _Giardiasis.pdf
CDC. 2004b.www.cdc.gov/ncidod/dpd/parasites/cyclospora/factsht_ cyclospora.htm
CDC. 2004c. www.cdc.gov/ncidod/dbmd/diseaseinfo/escherichiacoli_g.htm
CDC. 2004d. www.cdc.gov/ncidod/dbmd/diseaseinfo/salmonellosis_g.htm
CDC. 2004e. www.cdc.gov/ncidod/dbmd/diseaseinfo/campylobacter_g.htm
CDC. 2004f. www.cdc.gov/ncidod/dbmd/diseaseinfo/cholera_g.htm
CDC. 2005a. www.cdc.gov/ncidod/diseases/hepatitis/a/fact.htm
CDC. 2005b. www.cdc.gov/ncidod/dvrd/revb/gastro/noro-qa.pdf
CDC. 2005c. www.cdc.gov/ncidod/dpd/parasites/cryptosporidiosis/factsht_ cryptosporidiosis.htm
CDC. 2005d. www.cdc.gov/ncidod/dbmd/diseaseinfo/shigellosis_g.htm
CDC. 2005e. www.cdc.gov/travel/water_treatment.htm
Craun, G., Calderon, R.L., and Nwachuku, N. Causes of Waterborne Outbreaks Reported in the United States, 1991–1998. In: Drinking Water and Infectious Disease, Establishing the Links. 2003. CRC Press LLC, London.
Nelson, K.E. Emerging and New Infectious Diseases. 2004. In: Infectious Disease Epidemiology, Theory and Practice, Kenrad E. Nelson, Carolyn M. Williams, and Neil M.H. Graham, Eds. Jones and Bartlett Publishers.
Ohio Department of Health. 2005. www2.odh.ohio.gov/Data/ Inf_Dis/idann/Idsum03/03annsum.pdf
Summers, Judith. 1989. Soho—A History of London’s Most Colourful Neighborhood, Bloomsbury, London, pp. 113-117.
Todar, K. 2002. Todar’s Online Textbook of Bacteriology. textbookofbacteriology.net/cholera.html
WHO. 2004. www.who.int/water_sanitation_health/diseases/burden /en/index.html
Click here for PDF version of this Fact Sheet.
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