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A Norwalk-like virus outbreak on the Appalachian Trail. (Features).


Each year, more than 2,500 men and women attempt to backpack the 2,160 miles of the Appalachian Trail Appalachian Trail, officially Appalachian National Scenic Trail, hiking path, 2,144 mi (3,450 km) long, passing through 14 states, E United States.  from Springer Mountain Springer Mountain, 3,820 ft (1,164 m) high, N Ga. It is the southernmost peak of the Blue Ridge Mts. and the southern terminus of the Appalachian Trail.  in northern Georgia to Mount Katahdin Mount Katahdin (USGS name) is the highest mountain in Maine. Called Katahdin by people local to the peak and by the Penobscot Indians: the term means "The Greatest Mountain".  in central Maine. Only one in 10 of these "through-hikers" complete the trip, which can take, on average, almost six months (Appalachian Trail Conference, 1994; Center for Appalachian Trail Studies, 1999; Crouse & Josephs, 1993). Long-distance hikers face a number of challenges posed by weather, terrain, and insect or animal vectors, Hikers must also contend with the metabolic demands of daily hiking as well as the demand for potable potable /pot·a·ble/ (po´tah-b'l) fit to drink.

Fit to drink; drinkable.


fit to drink.
 water. Over 80 percent of Appalachian Trail hikers experience injury or illness, with an average of 1.8 health problems per hiker (Crouse & Josephs, 1993). Furthermore, injuries or illnesses occur in locations remote from sources of medical care.

Among the most common health effects reported by serious hikers and other wilderness recreationists are musculoskeletal musculoskeletal /mus·cu·lo·skel·e·tal/ (-skel´e-t'l) pertaining to or comprising the skeleton and muscles.

Relating to or involving the muscles and the skeleton.
 or soft-tissue injuries (which represent 50 to 70 percent of health effects) and illnesses and gastrointestinal problems (which represent 20 to 30 percent of health effects) (Montalvo, Wingard, Bracker, & Davidson, 1998; Crouse & Josephs, 1993; Gentile, Morris, Schimelpfenig, Bass, & Auerbach, 1992). Long-distance trails usually have limited sanitation facilities and limited or contaminated contaminated,
v 1. made radioactive by the addition of small quantities of radioactive material.
2. made contaminated by adding infective or radiographic materials.
3. an infective surface or object.
 water supplies that increase the risk of gastroenteritis gastroenteritis: see enteritis.

Acute infectious syndrome of the stomach lining and intestines. Symptoms include diarrhea, vomiting, and abdominal cramps.
 from viral, parasitic, or bacterial pathogens. Pathogens such as Norwalk-like viruses, Campylobacter jejuni Campylobacter jejuni Vibrio jejuni, Campylobacter fetus ssp jejuni A curved or spiral gram-negative bacillus with a single polar flagellum Epidemiology Linked to contact with domestic and farm animals, unpasteurized milk, primates, day care , and Ciardia lamblia have been documented as causes of gastroenteritis among campers and hikers (Jenkins, Herman, Israel, Cukor, & Blacklow, 1985; Taylor, McDermott, Little, Wells, & Blaser, 1983; Crouse & Josephs, 1993; Wilson, Anderson, Holman, Gary, & Greenberg, 1982).

Norwalk-like viruses, also known as human caliciviruses, are an important cause of acute gastroenteritis, especially in settings like schools, child care centers, nursing homes, hospitals, restaurants, cruise ships This is a list of cruise ships, both those in service and those that have since ceased to operate. Both cruise ships and cruiseferries are included in this list. (Ocean liners are not included on this list, see List of ocean liners. , military settings and summer camps. The incubation period incubation period
1. See latent period.

2. See incubative stage.

Incubation period 
 of this virus can be from several hours to several days, followed by an abrupt onset of nausea, vomiting, or diarrhea. Illness can last up to 48 hours with sequelae-free recovery (Hunter, 1997). Norwalk-like virus can be spread rapidly from person to person (Sharp et al., 1995; Stevenson, McCann, Duthie, Glew, & Ganguli, 1994); through food that has been handled by an infected person (Griffin et al., 1982; Nelson et al., 1992; Patterson, Hutchings, & Palmer, 1993); through exposure to recreational water (Baron et al., 1982); or from a contaminated water supply (Beller et al., 1997; Kaplan, Goodman, Schonberger, Lippy, & Gary, 1982; Lawson et al., 1991; Wilson et al., 1982). Because of the highly infectious nature of this agent, it is often difficult to determine the source of transmission, be it person to person or a single point such as a water supply or a food item.

An outbreak of gastrointestinal illness occurred among hikers on the Appalachian Trail in Virginia during May and June 1999. The purpose of the investigation reported here was to determine the extent of the outbreak, its source, and the infectious agent infectious agent Pathogen, see there  responsible for illness among the hikers.


On Thursday, June 10, 1999, the Alleghany/Roanoke City Health Department received calls from two Appalachian Trail hikers who had become sick with nausea, diarrhea, and vomiting on the trail between Catawba and Troutville, Virginia Troutville is a town in Botetourt County, Virginia, United States. The population was 432 at the 2000 census. History
The Town of Troutville was established in 1956 and is located in Botetourt County, Virginia. In 1881, this area had no name.
. These hikers reported others being sick on the trail and their suspicion that the source of this illness was a general store frequented by the hikers in Catawba. On the next day, two additional hikers in the same section of the trail reported similar illness.

Health department staff immediately interviewed nine sick hikers in Troutville and found that these hikers had begun to feel ill one to two days after leaving Catawba to resume their hike. Many were convalescing in one of several motels found in Troutville. During the next two days, Health Department staff identified 36 additional hikers ill with similar symptoms.

The preliminary investigation suggested that the illness might have started in Catawba, a small town with an all-you-can-eat restaurant and two general stores (stores A and B). Hikers went to Store A for water, prepared sandwiches, and pizza or packaged food. The proprietors offered an area adjacent to the store for overnight camping and two water hydrants for bathing and drinking. A bathroom was available for the hikers. Most hikers also went to the all-you-can-eat restaurant in town during their stay.


Environmental Investigation

The local health department informed the proprietor of Store A of the possible outbreak and requested that the store post a notice of possible contamination of water supply until samples could be collected and analyzed. On the following day, water samples were collected from taps inside the store, from the backyard hydrant (Hydrant A), and from the nearby feedlot feedlot

a management system in which naturally grazing animals are confined to a small area which produces no feed and are fed on stored feeds. See also dry lot.

backgrounding feedlot
 hydrant (Hydrant B) to be tested for total and fecal coliforms Fecal coliforms (sometimes faecal coliforms) are facultatively-anaerobic, rod-shaped, gram-negative, non-sporulating bacteria. They are capable of growth in the presence of bile salts or similar surface agents, oxidase negative, and produce acid and gas from lactose within  according to according to
1. As stated or indicated by; on the authority of: according to historians.

2. In keeping with: according to instructions.

 standard methods (American Public Health Association The American Public Health Association (APHA) is Washington, D.C.-based professional organization for public health professionals in the United States. Founded in 1872 by Dr. Stephen Smith, APHA has more than 30,000 members worldwide.  [APHA], 1998). Both backyard hydrants are in the camping area behind the store. In addition, inspectors were called in to observe food-handling practices and to monitor food temperatures during storage. Food handlers were interviewed to elicit any history of recent illness, to assess procedures used for food preparation, and to identify food sources. No food items from previous meals remained for laboratory analysis. During this visit, the owner of Store A was asked to voluntarily stop supplying water to the public.

In addition to samples collected from Store A, water was sampled from a nearby restaurant, the local post office, and four homes located near the store to determine if there was more extensive contamination of the water table in the immediate area. Concurrently, the local health department contacted the Roanoke Appalachian Trail Club to request assistance in posting advisories on the trail for hikers to filter and treat all water supplies, including well water.

On a third inspection of the store, a fluorescein dye Fluorescein dye
An orange dye used to illuminate the blood vessels of the retina in fluorescein angiography.

Mentioned in: Angiography
 was flushed down the toilet iii the store to see if the dye would later appear in the potable water system and thus indicate a hydrologic connection between the septic system and the well. A 10-gallon water sample was collected from the sink in store A and sent to the Center for Pediatric Research Pediatric Research is one of the most respected peer-reviewed medical journals within the field of pediatrics in the world.

It is the official publication of the American Pediatric Society, the European Society for Paediatric Research, and the Society for Pediatric
 at Eastern Virginia Medical School Coordinates:  Eastern Virginia Medical School, in Norfolk, Virginia is a public medical school.  in Norfolk, Virginia Norfolk is an independent city in the Commonwealth of Virginia, in the United States of America. With a population of 234,403 as of the 2000 census, Norfolk is Virginia's second-largest incorporated city. , to test for Norwalk-like viruses.

Epidemiologic Investigation

Because most hikers had become ill on the trail between Catawba and Troutville, the investigation focused on potential exposures occurring two days before and two days after hikers entered the town of Catawba. Using information from the Appalachian Trail Conference on average rates of travel over portions of the trail, the authors estimated that hikers could be intercepted in Waynesboro, Virginia Waynesboro, deriving its name from General Anthony Wayne or possibly Wayne's family home, is an independent city located within the confines of Augusta County in the U.S. state of Virginia. The population was 19,520 at the 2000 census, and estimated at 21,454 for 2006. , where the Appalachian Trail crosses the Blue Ridge Parkway The Blue Ridge Parkway is a National Parkway and All-American Road in the United States, noted for its scenic beauty. It runs for 469 miles (755 km) through the famous Blue Ridge, a major mountain chain that is part of the Appalachian Mountains. . A team from the health department set up a station at the crossing and conducted interviews from June 16 through June 20. In order to find hikers who might have arrived in the area a day or two earlier, hotels, motels, and campgrounds in the Waynesboro area were visited. Information on hikers who were further behind on the trail, as well as on those already heading out of Waynesboro, was obtained during the interviews.

A questionnaire solicited information on date of symptom onset, duration and characteristics of symptoms, foods consumed at Store A and at the restaurant, location of campsite two days before entering Catawba and two days after, and sources and amount of water consumed during the time period of interest. Additional information was sought on whether the hikers were traveling alone or in groups and whether they had shared food and water with other hikers. Six hikers who had been ill submitted stool specimens to be tested for enteric enteric /en·ter·ic/ (en-ter´ik) within or pertaining to the small intestine.

1. Of, relating to, or within the intestine.

 pathogens. Acute and convalescent serum convalescent serum Serum from a person who has recuperated from a particular infection–eg, scarlet fever, which may be of use in treating a person with the same infection; while acute-phase serum has ↑ IgM antibodies, CS has ↓ IgM, and  specimens were collected from eight hikers.

A person with a case was defined as any long-distance hiker in the state of Virginia reporting symptoms of diarrhea or vomiting with onset of symptoms on or after May 1. Relative risks (RR) and corresponding 95 percent confidence intervals [CIs] were calculated for consumption of specific food items from the general store or the restaurant, consumption of prepared items from the general store, consumption of other food along the trail, amount and source of water consumed, use of water filter, and travel pattern (alone or in a group). Data were analyzed with Epi Info Epi Info is a public domain statistical software for epidemiology developed by Centers for Disease Control and Prevention.

Developed by the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia (USA), Epi Info has been in existence for over 20 years and is
, Version 6 (Dean et al., 1996).

Laboratory Investigation

Six stool specimens were tested for common enteric bacterial, parasitic, and viral pathogens, including Salmonella, Shigella shigella

Any of the rod-shaped bacteria that make up the genus Shigella, which are normal inhabitants of the human intestinal tract and can cause dysentery, or shigellosis. Shigellae are gram-negative (see gram stain), non-spore-forming, stationary bacteria. S.
, Campylohacter, E. coli E. coli: see Escherichia coli.
E. coli
 in full Escherichia coli

Species of bacterium that inhabits the stomach and intestines. E. coli can be transmitted by water, milk, food, or flies and other insects.
 0157:H7, Crypto-sporidium parvum, Giardia lamblia Giardia lamblia
 or G. intestinalis

Single-celled protozoan parasite. Pear- or beet-shaped, the cells have two nuclei and eight flagella and attach with a sucking organ to human intestinal mucous membranes. They cause the disease giardiasis.
, and Norwalk-like virus, by the Epidemiologic Support Group in the Virginia State Laboratory Division of Consolidated Laboratory Services (DCLS DCLS Data Collection and Location System
DCLS Direct Current Level Shift
) in Richmond, Virginia Richmond IPA: [ɹɯʒmɐnɖ] is the capital of the Commonwealth of Virginia, in the United States. . Standard microbiological procedures were used for the laboratory analyses (APHA, 1998). Serum specimens were tested for antibodies against Norwalk-like viruses at the Center for Pediatric Research (CPR Cardiopulmonary Resuscitation (CPR) Definition

Cardiopulmonary resuscitation (CPR) is a procedure to support and maintain breathing and circulation for a person who has stopped breathing (respiratory arrest) and/or whose heart has stopped (cardiac
) in Norfolk, Virginia. The test for Norwalk-like virus in stool specimens was repeated at CPR. All water samples were tested for fecal coliform bacteria coliform bacteria

Rod-shaped bacteria usually found in the intestinal tracts of animals, including humans. Coliform bacteria do not require but can use oxygen, and they do not form spores. They produce acid and gas from the fermentation of lactose sugar.
 at DCLS. The 10-gallon water sample collected from inside Store A also was tested for Norwalk-like viruses in the CPR.

Reverse transcription-polymerase chain reaction (RT-PCR RT-PCR

reverse transcriptase-polymerase chain reaction. See PCR1.
) was used to detect Norwalk-like viruses in stool and water samples. A primer pair designed in the RNA polymerase RNA polymerase
A polymerase that catalyzes the synthesis of RNA from a DNA or RNA template.
 region highly conserved among Norwalk-like viruses was used in RT-PCR (Jiang et al, 1999; Jiang et al., 2000). Viral RNA RNA: see nucleic acid.
 in full ribonucleic acid

One of the two main types of nucleic acid (the other being DNA), which functions in cellular protein synthesis in all living cells and replaces DNA as the carrier of genetic
 was extracted from the stool specimens by the Trizol method before RT-PCR was performed (Farkas et al., 2000), while viruses in the water samples were concentrated by filtering of the samples through a positively charged filter before extraction of viral RNA (Huang et al., 2000). RT-PCR products were analyzed by gel electrophoresis, and DNA DNA: see nucleic acid.
 or deoxyribonucleic acid

One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes.
 bands in the gel were visualized under UV light. RTPCR RTPCR Reverse Transcriptase Polymerase Chain Reaction  products from positive specimens were then cloned and sequenced.

Serum specimens were tested for antibodies to Norwalk-like viruses with recombinant enzyme immunoassays (EIAs) specific for four strains of Norwalk-like viruses (Norwalk virus Nor·walk virus
A norovirus.

Norwalk virus (nôr´wôlk),
 [NV]; Hawaii virus [HV]; Mexico virus [MxV]; and Grimsby virus [GrV]). A seroresponse was defined as a fourfold or greater increase of the antibody titer antibody titer The amount of a specific antibody present in the serum, usually as a result of an acquired infection; titers for IgM usually rise abruptly at the time of infection–acute phase and fall slowly; during the 'convalescent' phase, IgG ↑ and is  in a convalescent con·va·les·cent
Relating to convalescence.

A person who is recovering from an illness, an injury, or a surgical operation.


1. pertaining to or characterized by convalescence.

 patient over the antibody titer of serum specimens taken from the same patient during acute illness.


Environmental Sampling

The water supply for the taps inside Store A and for hydrants A and B, outside Store A, was a hand-dug, shallow well. An ultraviolet light Ultraviolet light
A portion of the light spectrum not visible to the eye. Two bands of the UV spectrum, UVA and UVB, are used to treat psoriasis and other skin diseases.
 had been installed to purify the store's drinking water drinking water

supply of water available to animals for drinking supplied via nipples, in troughs, dams, ponds and larger natural water sources; an insufficient supply leads to dehydration; it can be the source of infection, e.g. leptospirosis, salmonellosis, or of poisoning, e.g.
 and had been in operation for three years without replacement. Store A is a convenience store with no indoor seating, so the Virginia Department of Agriculture and Consumer Services is responsible for inspection of the water supply. Water samples from the two outside hydrants (hydrants A and B) were positive for total and fecal coliform bacteria (Table 1). These samples were taken when the ultraviolet light system was in working order. The samples taken from the sink in the food preparation area inside Store A tested positive for total coliform bacteria. Water samples from a nearby post office and four nearby homes also were positive for total coliform bacteria. Water samples from the nearby restaurant tested negative for total coliform bacteria (Table 1). In addition, the environmental inspection of Store A identifie d no major deficiencies in food-handling practices or food temperatures during storage or preparation.

The distance from the septic system to the well was estimated to meet the standard of 100 feet, and no fluorescent dye was detected in the water supply, suggesting no connection with the septic system. The area is heavily agricultural, so it is likely that for the five contaminated wells and Store A, the sources of groundwater contamination were primarily agricultural. It is also possible that a leaking or failing neighboring septic system contributed to the problem. In addition to changing the ultraviolet light in the purification system of Store A, a chlorine treatment was applied, and water samples subsequently taken from the store demonstrated no contamination. The proprietor was advised to add a chlorinator to the system, and further sampling was recommended. Although the epidemiologic investigation was conducted to determine the source of the outbreak, no further investigations were conducted to determine the source of well contamination.

Epidemiologic Investigation

The authors interviewed 70 long-distance hikers from June 16 through June 20. Their ages ranged from 19 to 66 years, with a median age of 26 years, and 46 (65.7 percent) were male. Among the hikers interviewed, 45 (64.3 percent) met the case definition for illness. The earliest onset of illness reported was May 1, with two cases reported in the latter part of May. A cluster of 29 cases occurred between May 31 and June 10, and a second peak occurred between June 14 and June 16, the date of the last reported case (Figure 1). The predominant symptoms were diarrhea (in 88.9 percent of cases), nausea (in 84.4 percent of cases), and vomiting (in 60.0 percent of cases). Almost half of the ill persons reported fever, although no temperatures were measured (Table 2). Symptoms lasted for two to 72 hours, with a median duration of 24 hours.

Of the 45 ill hikers interviewed, seven had become ill before arriving in Catawba and 38 after. Among the 38 who became ill after reaching Catawba, one became ill before leaving Catawba, 35 became ill within two days of arriving in Catawba, one became ill within six days, and one became ill within 12 days.

People who had consumed food items like pizza or sandwiches that were prepared at General Store A were almost twice as likely to become ill as people who did not consume those foods (RR = 1.8; 95 percent CI: 1.0-3.2) (Table 3). No specific food item was, however, associated with illness. Consumption of water from the store was also associated with illness (RR = 1.7; 95 percent CI: 1.0-2.7). Thirty-five out of 51 people (68.6 percent) who consumed food prepared at the store or drank the water became ill, compared with none out of nine who either completely bypassed the store or consumed only prepackaged pre·pack·age  
tr.v. pre·pack·aged, pre·pack·ag·ing, pre·pack·ag·es
To wrap or package (a product) before marketing.

Adj. 1.
 drinks and food.

Eating at the all-you-can-eat restaurant in Catawba was not associated with illness. Approximately 50 percent of respondents who ate there became ill, compared with 62 percent of respondents who did not eat there (RR = 0.8; 95 percent CI: 0.6-1.2). Consuming food left by "trail angels" or sympathetic local residents (canned sodas, homemade brownies, homemade peanut-butter-and-jelly sandwiches) at a location about a half-day hike from Catawba was not associated with illness (RR = 1.0; 95 percent CI: 0.6-1.6).

The majority of hikers filtered or purified their drinking water (73 percent), some used iodine or chlorine to treat water (15 percent), several used a combination of methods (three percent), and a small minority did not filter their water at all (nine percent). Only one person filtered the drinking water at the store; most assumed that this source provided potable water. Hikers who filtered their water were slightly more likely to become ill than those who drank "raw" water. Traveling alone conveyed a small protective effect over traveling in groups of two or more, although the effect was not statistically significant (RR = 0.7; 95 percent CI: 0.4-1.3). Finally, camping overnight at Store A was associated with a 50 percent increased risk of illness compared with not camping at the store (RR = 1.5; 95 percent CI: 1.0-2.1).

Laboratory Results

Of the six stool samples submitted to DCLS, three were positive for Norwalk-like virus, and one was positive for Campylobacter jejuni. The RT-PCR result for Norwalk-like virus was confirmed at CPR; four out of the six samples were positive. One of the RT-PCR products was cloned and sequenced and the sequence revealed 77 percent nucleotide identity with Norwalk virus, suggesting that the outbreak was associated with genogroup I Norwalk-like viruses. All patients had seroresponses to genogroup I (NV). Seventy-five percent, 63 percent, and 63 percent had responses to members of genogroup II--HV, MxV, and GrV, respectively. These results confirmed the RT-PCR indication that a genogroup I Norwalk-like virus was associated with the outbreak. The water sample taken from Store A resulted in a single band of RT-PCR product of size similar to that of Norwalk-like virus products. The sequences of the product, however, revealed a less-than-50-percent nucleotide identity with known Norwalk-like viruses. This band may have been amplified from nucleic acids Nucleic acids
The cellular molecules DNA and RNA that act as coded instructions for the production of proteins and are copied for transmission of inherited traits.
 of unrelated organisms in the water supply.


Because of the unique setting, which allowed a portion of the cohort to be intercepted at a particular geographical and temporal location, the authors were able to determine the extent of the outbreak and the agent responsible. Clinical features of Norwalk-like virus infection matched the description of illness given by the hikers, and laboratory diagnosis detected Norwalk-like viruses in stool samples as well as antibodies to Norwalk-like viruses in the sera of hikers involved in the outbreak.

The authors successfully identified Norwalk-like virus in stool and sera but not in the water sample taken from the store. The process of examining water and wastewater for enteric viruses is still considered experimental. The low levels of virus contained in drinking water or recreational water require large sample volumes to increase the probability of virus detection (APHA, 1998), and the sample taken for this study may not have been large enough. Thus, the authors could not definitively implicate im·pli·cate  
tr.v. im·pli·cat·ed, im·pli·cat·ing, im·pli·cates
1. To involve or connect intimately or incriminatingly: evidence that implicates others in the plot.

 the water supply at Store A as the point source of the outbreak, despite positive results from fecal-coliform tests.

Nevertheless, contamination of Store A's water supply posed a potential risk to health. Evidence implicating im·pli·cate  
tr.v. im·pli·cat·ed, im·pli·cat·ing, im·pli·cates
1. To involve or connect intimately or incriminatingly: evidence that implicates others in the plot.

 the store came from the finding that almost 70 percent of hikers who consumed food or drank water at Store A became ill, whereas no illness occurred among those who bypassed the store or who ate only prepackaged food. No specific food items were, however, implicated im·pli·cate  
tr.v. im·pli·cat·ed, im·pli·cat·ing, im·pli·cates
1. To involve or connect intimately or incriminatingly: evidence that implicates others in the plot.

. Although the hikers also gathered at the nearby restaurant, the authors found no association between having eaten at the restaurant and illness. An additional complication was that the proprietor of Store A became ill with diarrhea during, but not before, the outbreak. Because he was responsible for cleaning up the campground behind the store, he may have become infected from the hikers and, while ill, may have spread the infection by working in food preparation. Environmental surface contamination in the store and in the surrounding camping area may have been factors in the persistence of the outbreak.

An important factor for the argument against the Store A as the source of the outbreak is that several sporadic cases of illness were reported during May, prior to the peak of the outbreak (Figure 1). Norwalk-like virus infection is extremely contagious, with very high attack rates. The attack rate in this cohort was 64 percent. Given the extremely infectious nature of this organism and the opportunity presented by the gathering of hikers at Store A, it is likely that Store A might have provided the opportunity for the virus to spread very rapidly rather than have been the initial source of this outbreak.

The nature of hiking on the Appalachian Trail presented the authors with a cohort that could be intercepted and interviewed in one location. All hikers who intended to continue on the trail or who were traveling into town to take a break had to pass the interviewing station. No hiker refused to participate. In addition, the authors canvassed hotels, campgrounds, and parks in Waynesboro to find hikers who had been in town a day or two earlier. They also searched further along the trail and found hikers at the next campground. Nevertheless, they may have missed hikers who had become ill and ended their hike or who had dropped out before interviewing began.


This research suggests that health problems among hikers, specifically gastrointestinal illness, may be difficult to control. Traditional public-health methods of reducing the risk of infectious disease Infectious disease

A pathological condition spread among biological species. Infectious diseases, although varied in their effects, are always associated with viruses, bacteria, fungi, protozoa, multicellular parasites and aberrant proteins known as prions.
 are difficult to apply in this setting. Water is not plentiful, so regular handwashing can be impossible. Filtering water is time consuming, so filtered water is used for drinking but not for washing. Boiling water also presents difficulties in terms of obtaining fuel and in the amount of water that can be disinfected Disinfected
Decreased the number of microorganisms on or in an object.

Mentioned in: Isolation
 given the small scale of equipment carried by hikers. Several hikers used iodine or chlorine for disinfection disinfection,
n the process of destroying pathogenic organisms or rendering them inert.

disinfection, full oral cavity,
n a procedure used to reduce active periodontal disease, usually completed within a certain short time frame.
 and expressed concern over the use of iodine for purification. The use of iodine tablets often produces moderately high levels of residual iodine, and such use should be limited to three months (Backer & Hallowell, 2000). Products that use charcoal scavengers to remove residual iodine are available and make this method acceptable for long-term use. In the case of person-to-person transmis sion, however, which is thought to be the source of this outbreak, filtering of water would not have provided protection against becoming ill.

Educating hikers on the nature of the Norwalk-like virus infection and potential risk factors in different environmental settings may help reduce risk and control outbreaks. Hikers should be aware that not all water sources in town are free from contamination -- especially those that rely on well water. Most hikers in this study did not filter water while in town because they assumed the water was potable. Routine inspection and monitoring of public water supply systems is critical to maintaining a safe water supply Nevertheless, wells in heavily agricultural areas can be contaminated by runoff from barns or fields.

As with any situation in which sanitation is poor and water is scarce, the risk of gastrointestinal illness increases with crowding and contact. This is suggested by the lower risk of illness incurred by those who either traveled alone or avoided camping at Store A, where opportunity for contact was highest.


Water Samples Obtained from Store A and Surrounding Areas

Date     Location           Results

6/11/99  Backyard hydrant   500 MPN total coliforms (*)
6/11/99  Backyard hydrant   900 MPN total coliforms
6/11/99  Feedlot hydrant    500 MPN fecal coliforms (**)
6/11/99  Feedlot hydrant    500 MPN fecal coliforms
6/14/99  Hand sink          Positive total coliforms (+)
6/15/99  Nearby restaurant  Negative total coliforms
6/15/99  Post office        Positive total coliforms
6/15/99  Four nearby homes  Positive total coliforms
6/15/99  Four nearby homes  Positive fecal coliforms (++)

(*)Read as 500 = most probable number (MPN) of total coliform organisms.

(**)Read as 500 = MPN of fecal coliform organisms.

(+)Read as positive or negative for total coliform organisms

(++)Read as positive for fecal coliform organisms (nonquantitative).

Symptoms Reported in Appalachian Trail Outbreak

Symptom   Number of Cases

Diarrhea    40 (88.9%)
Nausea      38 (84.4%)
Vomiting    27 (60.0%)
Fever       21 (46.7%)
Cramps      15 (33.3%)
Headache    12 (26.7%)

Relative Risk and 95% Confidence Intervals for Food or Water Consumption
and Hiker Travel Patterns

Consumption/Travel Characteristics  Relative Risk   95% CI

Food prepared at Store A                 1.8       (1.0-3.2)
Food from nearby restaurant              0.8       (0.6-1.2)
Food left by "trail angels"              1.0       (0.6-1.6)
Water from Store A                       1.7       (1.0-2.7)
Traveling alone                          0.7       (0.4-1.3)
Filtering or treating water              1.9       (0.6-5.9)
Camping overnight at Store A             1.5       (1.0-2.1)

Acknowledgements: The authors thank Dick Tabb, David Taylor, Sandy Moore, Jackie Zeltvay, and Karen Chaples of the Alleghany/Roanoke City Health District; Robert Tate of the Virginia Department of Health; John Dansby of the Division of Consumer Protection; Sue Yager of the Pennsylvania Department of Health; Robert Proudman and James Hutchings of the Appalachian Trail Conference; Hal Cantrill of the Roanoke Appalachian Trail Club; Brian Cagle, Public Health Consultant for the National Park Service; and, last but not least, the 1999 Appalachian Trail hikers.


American Public Health Association. (1998). Standard methods. Washington, DC: Author.

Appalachian Trail Conference. (1996). History of the Appalachian Trail Project. (30 Dec. 2001).

Backer, H., & Hollowell, J. (2000). Use of iodine for water disinfection: Iodine toxicity and maximum recommended dose maximum recommended dose (MRD),
n the highest amount of an anesthetic agent that can be given safely and without complication to a patient while maintaining its efficacy.
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intr.v. dick·ered, dick·er·ing, dick·ers
To bargain; barter.

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External links
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Brit a moist spicy ginger cake usually containing oatmeal [origin unknown]
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New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of
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  • Morbidity and Mortality Weekly Report, a medical publication
See also
  • Morbidity, a medical term
  • Mortality, a medical term
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Nelson, T.L., Wright, T.L., Case, M.A., Martin, D.R., Glass, R.I., & Sangal, S.P (1992). A protracted pro·tract  
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Wilson, R., Anderson, L.J., Holman, R.C., Gary, G.W, & Greenberg, H.B. (1982). Waterborne gastroenteritis due to the Norwalk agent Norwalk agent(s) Montgomery County virus, Norwalk virus Virology Any of a group of 27 nm parvoviruses–single-stranded DNA viruses of the Caliciviridae family, which cause 'winter vomiting disease', first described in Norwalk, Ohio, incriminated in up to 40% : Clinical and epidemiologic investigation. American Journal of Public Health The American Journal of Public Health (AJPH) is a peer reviewed monthly journal of the American Public Health Association (APHA). The Journal also regularly publishes authoritative editorials and commentaries and serves as a forum for the analysis of health policy. , 72(1), 72-74.

Corresponding Author: Lucy A. Peipins, Ph.D., Agency for Toxic Substances and Disease Registry The United States Agency for Toxic Substances and Disease Registry, (ATSDR) is an agency for the U.S. Department of Health and Human Services that is directed by a congressional mandate to perform specific functions concerning the effect on public health of hazardous , 1600 Clifton Rd., NE, E-31, Atlanta, GA 30333. E-mail: <>.
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Author:Jiang, Xi
Publication:Journal of Environmental Health
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Date:May 1, 2002
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