Epidemic campylobacteriosis associated with a community water supply.

In May 1983, an estimated 865 cases of epidemic gastrointestinal disease occurred in Greenville, Florida. Surveillance of pharmacy sales of antidiarrheal medicines suggested that the outbreak was confined to Greenville and its immediate vicinity. Surveys demonstrated that the gastrointestinal illness attack rates inside and outside the city limits were 56 per cent (72/128) and 9 per cent (7/77), respectively (relative risk (RR) = 6.2); consumption of city water was associated with illness (RR = 12); and as water consumption increased, the attack rate also increased (p less than 0.001). Four adults were hospitalized and one outbreak-related case of Guillain-Barre' syndrome was identified. Campylobacter jejuni was isolated from specimens from 11 ill persons; serologic studies showed the development of Campylobacter-specific antibodies. Fecal coliforms were found in water samples, but Campylobacter was not recovered from water. The city water plant, a deep well system, had numerous deficiencies including an unlicensed operator, a failure of chlorination, and open-top treatment towers. Birds were observed perching on the open-top treatment tower. Of 38 birds trapped seven weeks later, 37 per cent harbored C. jejuni; however, plasmid and serotyping studies showed that strains were not the same as the common strain from ill persons. This outbreak suggests that water systems that are unprotected from contact with birds may become contaminated and a source of outbreaks of human campylobacteriosis.     

Shigellosis outbreak associated with swimming

In June 1982, an outbreak of gastrointestinal illness caused by Shigella sonnei occurred among residents of two counties in Oklahoma. A case-control study of cases and age and sex-matched controls showed an association with attendance at a southern Oklahoma lake (14/17 cases vs 3/17 controls, matched pair odds ratio [OR] 9/0, confidence interval [CI] 2.4-infinity). A survey of 85 persons who had visited the lake area showed that persons who had swum were more likely to have been ill with a gastrointestinal illness (50 per cent) than persons who had not swum (0 per cent); among those who had swum, illness was more frequent among those who reported having water in their mouths while swimming (62 per cent) than those who did not (19 per cent) (OR = 6.9, 95% CI = 2.2-21.5). No further primary lake-associated cases had onset of symptoms beyond two days of closing the reservoir. Swimming should be considered as a potential source of enteric infections.     

A large Clostridium perfringens foodborne outbreak with an unusual attack rate pattern

On November 7, 1985, a Clostridium perfringens gastroenteritis outbreak occurred in approximately 44% of the 1,362 employees at a Connecticut factory. Although the same foods were served to all three shifts at an employee banquet on November 6, the attack rate was almost twice as high for those who ate on the day shift (attack rate = 50%) than for those on the evening shift (attack rate = 20%) or night shift (attack rate = 29%). Among employees of the day shift, attack rates were highest for those who ate during the first 30 minutes of the 2.5-hour day shift serving period and decreased throughout the serving period. The one-hour evening shift serving period had a similar trend toward higher attack rates earlier in the serving period. Four main-course foods were significantly associated with illness, and over 95% of the employees had eaten each of them. Stratified analysis indicated that gravy was the responsible food and, furthermore, that the decreasing attack rate pattern within serving periods occurred only for those who ate gravy. The gravy had been prepared 12-24 hours in advance of banquet service. After it was prepared, the gravy was improperly cooled and was reheated shortly before and throughout the serving periods. Persons who ate gravy that had been reheated for the longest period of time had the lowest attack rate, probably because they were exposed to a lower concentration of organisms. This outbreak underscores the need for properly reheating food to prevent C. perfringens gastroenteritis and suggests that analysis of attack rate trends may provide important epidemiologic clues to understanding the causes of foodborne disease outbreaks.     

Diphtheria: a possible foodborne outbreak in Hodeida, Yemen Arab Republic

Between 29 August 1981 and 16 January 1982, an epidemic of diphtheria produced 149 cases in Hodeida, Yemen Arab Republic. The overall attack rate was 11.8 per 10 000; the most frequent victims were males under 5 years of age, with an attack rate of 55.7 per 10 000. Severity of the illness varied inversely with age and the number of previous doses of DPT. A case—control study showed that vaccination with DPT was protective (P = 0.03) with an efficacy of 87.3% (95% confidence interval, 32.2-99.5%) among those who had received 3 or more doses. Risk factors for the development of disease were previous contact with a case (P = 0.002), previous contact with a person having skin disease (P = 0.04), obtaining drinking-water from a wheeled carrier (P = 0.008), and consumption of factory-made yoghurt (P = 0.003). The secondary attack rate among household contacts under 15 years of age was at least 1.3%.     

The risk of acquiring hepatitis from sewage-contaminated water

There is little information on the risk of acquiring hepatitis A from drinking sewage-contaminated water. In a large outbreak of gastrointestinal illness at Crater Lake National Park, Oregon, a US national park, in June-July, 1975, approximately 100,000 persons were exposed to sewage-contaminated water. State health departments reported three cases of Crater Lake-associated hepatitis A for a rate of 12/100,000 per year, comparable to the reported US incidence of non-B hepatitis 10/100,000 per year. Questionnaire survey of 3997 overnight park visitors revealed five cases of hepatitis A, occurring in 2206 persons who drank water but did not receive immune serum globulin (ISG) within two weeks of exposure, an attack rate of 0.23%. The association between drinking park water and subsequently developing hepatitis was not statistically significant. No cases of hepatitis occurred in 320 park staff and family members, repeatedly exposed to contaminated water. The authors do not recommend routine use of prophylactic ISG for similar outbreaks of gastroenteritis caused by sewage-contaminated water but suggest close surveillance of the exposed group, and careful consideration of risk factors and costs.     

The epidemiology of influenza B in a rural setting in 1977.

An epidemic of influenza B began in January, 1977, in two rural parishes in northeastern Louisiana and quickly spread to involve 29% of their population with clinical influenza. This epidemic was investigated using a standard questionnaire and a random sample of 4.2% of the population. The clinical illness was typical of influenza, with predominant fever, cough, malaise and headache. Gastrointestinal symptoms were part of the clinical syndrome. Rhinitis and diarrhea were significantly more common in children aged five years or less. Clinical attack rates increased with larger household size. The youngest age groups had clinical attack rate of 40--55%, but the elderly had very low attack rates. The direct cost of influenza-like illness during the epidemic averaged almost $30.00 per case. Knowledge of the cost of influenza-like illness and age-specific attack rates should be useful in planning future control efforts for influenza B.     

An outbreak of measles in a rural Queensland town in 1997; an opportunity to assess vaccine effectiveness.

This report describes a measles outbreak in a rural town in south-east Queensland and presents the results of a vaccine effectiveness (VE) study performed during this outbreak. It is important to assess the effectiveness of a vaccine in an outbreak to determine if the outbreak is due to failure of the vaccine or failure to vaccinate. There were 44 cases of measles amongst local residents, which represents a notification rate of 396.7 per 100,000 population. Case investigations identified a group of people who had been exposed to measles at a seminar. The attack rate for the seminar cohort was 18% (11/61). This presented an opportunity to conduct a VE study using data about children aged less than 16 years who attended the seminar. In this cohort of 23 attendees, all 7 children who had not received any measles vaccinations became cases whilst the 6 who were fully vaccinated for their age according to NHMRC guidelines were protected from measles illness. Although there were insufficient fully vaccinated cohort members to reliably estimate VE for this group, the vaccine was 84.6% (95% CI: 15.0-99.7%) effective for those who had received at least one validated dose of vaccine. Despite the sample size limitations, the results support the view that failure to vaccinate rather than vaccine failure contributed to the high infection rate in the seminar cohort.     

A community waterborne outbreak of salmonellosis and the effectiveness of a boil water order.

OBJECTIVES: A 1993 large water-borne outbreak of Salmonella typhimurium infections in Gideon, Mo, a city of 1100 with an unchlorinated community water supply, was investigated to determine the source of contamination and the effectiveness of an order to boil water. METHODS: A survey of household members in Gideon and the surrounding township produced information on diarrheal illness, water consumption, and compliance with the boil water order. RESULTS: More than 650 persons were ill; 15 were hospitalized, and 7 died. Persons consuming city water were more likely to be ill (relative risk [RR] = 9.1, 95% confidence interval [CI] = 2.9, 28.4), and the attack rate increased with increased water consumption. S. typhimurium was recovered from samples taken from a city fire hydrant and a water storage tower. Persons in 31% (30/ 98) of city households had drunk unboiled water after being informed about the boil water order, including 14 individuals who subsequently became ill. Reasons for noncompliance included "not remembering" (44%) and "disbelieving" (25%) the order. CONCLUSIONS: Communities with deteriorating water systems risk widespread illness unless water supplies are properly operated and maintained. Effective education to improve compliance during boil water orders is needed.     

Oropharyngeal Tularemia Outbreak Associated with Drinking Contaminated Tap Water,Turkey, July–September 2013

In 2013, an oropharyngeal tularemia outbreak in Turkey affected 55 persons. Drinking tap water during the likely exposure period was significantly associated with illness (attack rate 27% vs. 11% among non–tap water drinkers). Findings showed the tap water source had been contaminated by surface water, and the chlorination device malfunctioned.     

Daily variations in effluent water turbidity and diarrhoeal illness in a Russian city

To assess an association between temporal variations in drinking water quality and gastrointestinal (GI) illness, a cohort study involving 100 randomly selected families (367 individuals) was conducted in the city of Cherepovets, Russia from June through November 1999. Participants maintained daily diaries of gastrointestinal symptoms, water consumption and other behavioural exposure variables, while daily effluent water quality data were provided by the water utility. The cumulative incidence rate of self-reported gastrointestinal diseases, 1.7 cases per person-year, was almost two orders of magnitude higher than that of officially reported GI infections in the city. An interquartile range increase in effluent water turbidity of 0.8 Nephelometric Turbidity Units was associated with a relative risk of self-reported GI illness of 1.47 (95% Confidence Interval 1.16, 1.86) at a lag of 2 days after control for daily rate of consumption of non-boiled tap water, behavioural covariates, day of the week and a seasonally-related linear trend. In the analysis by subsets of study participants stratified by non-boiled tap water consumption, no statistically significant associations between turbidity and GI illness were found for the study participants who always boiled their drinking water. For individuals who drank non-boiled tap water, statistically significant associations between turbidity and GI illness were detected at lags 1, 2 and 7 days.     

An outbreak of hepatitis A associated with an infected foodhandler

OBJECTIVE: The recommended criteria for public notification of a hepatitis A virus (HAV)-infected foodhandler include assessment of the foodhandler's hygiene and symptoms. In October 1994, a Kentucky health department received a report of a catering company foodhandler with hepatitis A. Patrons were not offered immune globulin because the foodhandler's hygiene was assessed to be good and he denied having diarrhea. During early November, 29 cases of hepatitis A were reported among people who had attended an event catered by this company. Two local health departments and the Centers for Disease Control and Prevention, in collaboration with two state health departments, undertook an investigation to determine the extent of the outbreak, to identify the foods and event characteristics associated with illness, and to investigate the apparent failure of the criteria for determining when immune globulin (IG) should be offered to exposed members of the public. METHODS: Cases were IgM anti-HAV-positive people with onset of symptoms during October or November who had eaten foods prepared by the catering company. To determine the outbreak's extent and factors associated with illness, the authors interviewed all case patients and the infected foodhandler and collected information on menus and other event characteristics. To investigate characteristics of events associated with transmission, the authors conducted a retrospective analysis comparing the risk of illness by selected event characteristics. To evaluate what foods were associated with illness, they conducted a retrospective cohort study of attendees of four events with high attack rates. RESULTS: A total of 91 cases were identified. At least one case was reported from 21 (51%) of the 41 catered events. The overall attack rate was 7% among the 1318 people who attended these events (range 0 to 75% per event). Attending an event at which there was no on-site sink (relative risk [RR] = 2.3, 95% confidence interval [CI] 1.4, 3.8) or no on-site kitchen (RR = 1.9, 95% Cl 1.1, 2.9) was associated with illness. For three events with high attack rates, eating at least one of several uncooked foods was associated with illness, with RRs ranging from 8 to undefined. CONCLUSION: A large hepatitis A outbreak resulted from an infected foodhandler with apparent good hygiene and no reported diarrhea who prepared many uncooked foods served at catered events. Assessing hygiene and symptoms s subjective, and may be difficult to accomplish. The effectiveness of the recommended criteria for determining when IG should be provided to exposed members of the public needs to be evaluated.     

2007年攀枝花市某农村中学1起细菌性痢疾暴发调查

[目的]了解和掌握2007年9月8～14日发生在攀枝花市仁和区某农村中学(初中)1起细菌性痢疾暴发疫情的特点,搞清暴发原因,为采取有效控制措施提供依据。[方法]2007年9月15日,到该中学进行调查。[结果]这起暴发共发病58例,均为学生,554名学生的罹患率为10.47%;从10份病人大便(肛拭)检出3株宋内氏志贺菌。细菌性痢疾罹患率,住校生高于走读生,男生高于女生,9月5～8日饮生水者高于不饮生水者,饮自备水生水者高于饮生活用水生水者,饮生水次数多者高于次数少者,喝豆浆次数多者高于次数少者,喝冷豆浆者高于喝热豆浆者,洗碗用自备水者高于用生活用水者(P<0.01或<0.05)。[结论]这是使用被污染的自备水源引起的1起细菌性痢疾暴发疫情。     

Epidemic giardiasis caused by a contaminated public water supply.

In the period November 1, 1985 to January 31, 1986, 703 cases of giardiasis were reported in Pittsfield, Massachusetts (population 50,265). The community obtained its water from two main reservoirs (A and B) and an auxiliary reservoir (C). Potable water was chlorinated but not filtered. The incidence of illness peaked approximately two weeks after the city began obtaining a major portion of its water from reservoir C, which had not been used for three years. The attack rate of giardiasis for residents of areas supplied by reservoir C was 14.3/1000, compared with 7.0/1000 in areas that received no water from reservoir C. A case-control study showed that persons with giardiasis were more likely to be older and to have drunk more municipal water than household controls. A community telephone survey indicated that over 3,800 people could have had diarrhea that might have been caused by Giardia, and 95 per cent of households were either using alternate sources of drinking water or boiling municipal water. Environmental studies identified Giardia cysts in the water of reservoir C. Cysts were also detected in the two other reservoirs supplying the city, but at lower concentrations. This investigation highlights the risk of giardiasis associated with unfiltered surface water systems.     

An outbreak of waterborne giardiasis associated with heavy water runoff due to warm weather and volcanic ashfall

From mid-June through early August 1980, an outbreak of gastrointestinal illness in Red Lodge, Montana affected approximately 780 persons, as estimated from attack rates of 33 per cent and 15 per cent in urban and rural residents, respectively. Giardia lamblia was identified in stool specimens from 51 per cent of 47 persons with a history of untreated gastrointestinal illness and in 13 per cent of 24 specimens from asymptomatic persons (p = .00045, Fisher's Exact Test). The epidemic curve was bimodal with peaks in mid-June and mid-July. Each peak occurred about three weeks after an episode of very heavy water runoff resulting from warm sunny weather and snow darkened by ashfall from the Mt. St. Helens volcanic eruption of May 18, 1980. Unfiltered and inadequately chlorinated surface water was supplied by the city water system, which was implicated as the vehicle of transmission in the outbreak. Water systems providing unfiltered surface water are more likely to become contaminated during periods of heavy water runoff.     

A waterborne outbreak of Escherichia coli O157:H7 infections and hemolytic uremic syndrome: implications for rural water systems

In the summer of 1998, a large outbreak of Escherichia coli O157:H7 infections occurred in Alpine, Wyoming. We identified 157 ill persons; stool from 71 (45%) yielded E. coli O157:H7. In two cohort studies, illness was significantly associated with drinking municipal water (town residents: adjusted odds ratio=10.1, 95% confidence intervals [CI]=1.8-56.4; visitors attending family reunion: relative risk=9.0, 95% CI=1.3-63.3). The unchlorinated water supply had microbiologic evidence of fecal organisms and the potential for chronic contamination with surface water. Among persons exposed to water, the attack rate was significantly lower in town residents than in visitors (23% vs. 50%, p<0.01) and decreased with increasing age. The lower attack rate among exposed residents, especially adults, is consistent with the acquisition of partial immunity following long-term exposure. Serologic data, although limited, may support this finding. Contamination of small, unprotected water systems may be an increasing public health risk.     

Acute rheumatic fever and the evolution of rheumatic heart disease: a prospective 12 year follow-up report.

Sixty four children who presented with the initial attack of acute rheumatic fever and maintained continuous regular secondary prophylaxis, were followed up prospectively for 12.3 years (an observation period of 775 patient-years). The prevalence rate of rheumatic heart disease in the 29 children who had carditis in the initial attack and in the 35 children who had no carditis initially was 49 vs 0%, respectively. The overall prevalence rate of rheumatic heart disease was 20%. Mitral incompetence developed in 11 patients (17%), aortic incompetence in 2 (3%) and mitral stenosis in 2 (3%). None of the patients developed aortic stenosis. Two recurrences developed with a recurrence rate of 0.003 per patient per year. One patient needed cardiac surgery and there was no mortality. These data strongly suggest that continuous regular secondary prophylaxis can prevent or significantly reduce the development of mitral and aortic valve stenosis, the prevalence rate of rheumatic heart disease and mortality.     

A Cryptosporidium hominis outbreak in North-West Wales associated with low oocyst counts in treated drinking water

An outbreak in the autumn of 2005 resulted in 218 confirmed cases of Cryptosporidium hominis. The attack rate (relative risk 4.1, 95%CI 2.8–9.1) was significantly higher in the population supplied by Cwellyn Water Treatment Works (WTW). A case–control study demonstrated a statistically significant association (odds ratio 6.1, 95% CI 1.8–23.8) between drinking unboiled tap water and C. hominis infection. The association remained significant in a logistic regression analysis, with an adjusted odds ratio of 1.30 (95 CI 1.05–1.61) per glass of unboiled tap water consumed per day. This evidence together with environmental and associated microbiological investigations, and the absence of effective treatment to remove Cryptosporidium oocysts at the WTW, led to the conclusion that the outbreak was waterborne. Oocyst counts in final treated water at the WTW and at different points in the distribution system were consistently very low, maximum count in continuous monitoring 0.08 oocysts per 10 litres. Data from continuous monitoring and the epidemic curve is consistent with the hypothesis that low numbers of oocysts of C hominis were present in treated water continuously during the outbreak and these were of sufficient infectivity to cause illness. All surface water derived water supplies present a potential risk to human health and appropriate control measures should be in place to minimise these risks.     

一起传染性非典型肺炎爆发的“超级传播者”和传播链分析

目的：了解严重急性呼吸综合征(SARS)爆发案例的传播过程，分析SARS病例不同阶段的传染性和不同接触方式的危险性。方法：设计统一调查表，用查阅病历、面对面调查和电话调查相结合的方式进行，以指征病例为起点进行线索追踪和个案调查。用传播链示意图分析传播关系，用接触史分析示意图分析传染性。结果：共追查到与该案例传播链相关的接触者207人，发病36例，死亡1例，总罹患率为17％。其中指征病例和1名二代病例分别直接传播了12例和13例续发病例，其传播过程可以用清晰的传播链加以描述；所有36例病例均与前代病例的症状期有密切接触史，家族传播链中85％的病例都与前代病例症状期的第3—5天有过接触，发病前后均接触和仅发病后接触者罹患率分别为70％和67％，差异无显著性；仅与前代病例潜伏期接触的15名同柜台同事、29名同班同学无发病，38名与医护人员发病前或发病初期密切接触的家属无发病。结论：该案例所有的续发病例都有与症状期病例密切接触史；未观察到SARS患者在其潜伏期内存在传染性。     

Urban yellow fever epidemic in western Nigeria, 1987

A large epidemic of urban yellow fever occurred in April and May 1987 in Oyo State, western Nigeria. The principal vector was Aedes aegypti, breeding in domestic water containers. The 1987 outbreak followed an epidemic of sylvatic yellow fever in eastern Nigeria the previous year, and probably resulted from introduction of the virus by viraemic travellers. The outbreak in Oyo State ended in early July, by which time 805 cases and 416 deaths had been officially notified. However, surveys of 3 villages in the epicentre, a region with over 4 million inhabitants, indicated an infection rate of approximately 20%, a clinical attack rate of 2.9% and a mortality rate of 0.6%, suggesting that the true incidence of cases and deaths far exceeded the official reports. Yellow fever virus was isolated from persons with fully developed yellow fever as well as mild febrile illness. One virus isolate was made from blood of an individual with mild illness, who had received 17D vaccine 5 d earlier; monoclonal antibody analysis showed that the isolate was a wild-type virus. Larval indices of Ae. aegypti were very high; however, low vector competence of the Ae aegypti population may have provided a constraint on spread of the epidemic. In late 1987 a third epidemic appeared in Niger State, northern Nigeria, with 644 reported cases and 149 deaths. The vector(s) involved is (are) unknown.     

一起小学校内乙型流感暴发的调查

2004年9月下旬，浙江省江山市某乡镇中心小学发生了一起由乙型流感病毒引起流行性感冒暴发。经调查本次乙型流感共发现患者65例，罹患率15．26％。