Tag Archives: waterborne disease

Cholera Outbreak in Vietnam from Unsafe Water

Nguyen TV, Pham QD, Do QK, Diep TT, Phan HC, Ho TV, Do HT, Phan LT, Tran HN. Cholera returns to southern Vietnam in an outbreak associated with consuming unsafe water through iced tea: A matched case-control study. PLoS neglected tropical diseases. 2017 Apr 13;11(4):e0005490. doi: 10.1371/journal.pntd.0005490.

BACKGROUND: After more than a decade of steadily declining notifications, the number of reported cholera cases has recently increased in Vietnam. We conducted a matched case-control study to investigate transmission of cholera during an outbreak in Ben Tre, southern Vietnam, and to explore the associated risk factors.

METHODOLOGY/PRINCIPAL FINDINGS: Sixty of 71 diarrheal patients confirmed to be infected with cholera by culture and diagnosed between May 9 and August 3, 2010 in Ben Tre were consecutively recruited as case-patients. Case-patients were matched 1:4 to controls by commune, sex, and 5-year age group. Risk factors for cholera were examined by multivariable conditional logistic regression. In addition, environmental samples from villages containing case-patients were taken to identify contamination of food and water sources. The regression indicated that drinking iced tea (adjusted odds ratio (aOR) = 8.40, 95% confidence interval (CI): 1.84-39.25), not always boiling drinking water (aOR = 2.62, 95% CI: 1.03-6.67), having the main source of water for use being close to a toilet (aOR = 4.36, 95% CI: 1.37-13.88), living with people who had acute diarrhea (aOR = 13.72, 95% CI: 2.77-67.97), and little or no education (aOR = 4.89, 95% CI: 1.18-20.19) were significantly associated with increased risk of cholera. In contrast, drinking stored rainwater (aOR = 0.17, 95% CI: 0.04-0.63), eating cooked seafood (aOR = 0.27, 95% CI: 0.10-0.73), and eating steamed vegetables (aOR = 0.22, 95% CI: 0.07-0.70) were protective against cholera. Vibrio cholerae O1 Ogawa carrying ctxA was found in two of twenty-five river water samples and one of six wastewater samples.

CONCLUSIONS/SIGNIFICANCE: The magnitude of the cholera outbreak in Ben Tre was lower than in other similar settings. This investigation identified several risk factors and underscored the importance of continued responses targeting cholera prevention in southern Vietnam. The association between drinking iced tea and cholera and the spread of V. cholerae O1, altered El Tor strains warrant further research. These findings might be affected by a number of limitations due to the inability to capture asymptomatic or mildly symptomatic infections, the possible underreporting of personal unhygienic behaviors, and the purposive selection of environmental samples.

Outbreak of Hepatitis A associated with Water Supply, Thailand

Ruchusatsawat K, Wongpiyabovorn J, Kawidam C, Thiemsing L, Sangkitporn S, Yoshizaki S, Tatsumi M, Takeda N, Ishii K. An Outbreak of Acute Hepatitis Caused by Genotype IB Hepatitis A Viruses Contaminating the Water Supply in Thailand. Intervirology. 2017 Feb 17;59(4):197-203. doi: 10.1159/000455856.

BACKGROUND: In 2000, an outbreak of acute hepatitis A was reported in a province adjacent to Bangkok, Thailand.

AIMS: To investigate the cause of the 2000 hepatitis A outbreaks in Thailand using molecular epidemiological analysis.

METHODS: Serum and stool specimens were collected from patients who were clinically diagnosed with acute viral hepatitis. Water samples from drinking water and deep-drilled wells were also collected. These specimens were subjected to polymerase chain reaction (PCR) amplification and sequencing of the VP1/2A region of the hepatitis A virus (HAV) genome. The entire genome sequence of one of the fecal specimens was determined and phylogenetically analyzed with those of known HAV sequences.

RESULTS AND CONCLUSIONS: Eleven of 24 fecal specimens collected from acute viral hepatitis patients were positive as determined by semi- nested reverse transcription PCR targeting the VP1/2A region of HAV. The nucleotide sequence of these samples had an identical genotype IB sequence, suggesting that the same causative agent was present. The complete nucleotide sequence derived from one of the samples indicated that the Thai genotype IB strain should be classified in a unique phylogenetic cluster. The analysis using an adjusted odds ratio showed that the consumption of groundwater was the most likely risk factor associated with the disease.

Investigating a Waterborne Outbreak of Cryptosporidiosis; Ireland

Mahon M, Doyle S. Waterborne outbreak of cryptosporidiosis in the South East of Ireland: weighing up the evidence. Ir J Med Sci. 2017 Jan 13. doi: 10.1007/s11845-016-1552-1.

BACKGROUND: In late Spring 2012, 12 cases of cryptosporidiosis in a town in the South East of Ireland were notified to the regional Department of Public Health.

AIM: The purpose of this paper is to describe the outbreak and the investigative process which led to the conclusion that the source was a public drinking water supply.

METHODS: Outbreak and incident control teams were convened to investigate and control the outbreak.

RESULTS: Eleven cases were speciated as Cryptosporidium parvum. GP60 analysis demonstrated that 10 were C. parvum IIaA20G3R1, indicating that the cases were linked. The public water supply was the only common risk factor identified. Increased water sampling identified Cryptosporidium muris/andersoni in the treated water at one of two water treatment plants (Water Treatment Plant, WTP A) for the supply, and on the network. C. parvum was subsequently identified in raw water from WTP A.

CONCLUSIONS: The Health Service Executive (HSE) concluded that this outbreak was “probably associated with water” produced at WTP A based on (1) descriptive epidemiological evidence suggesting water-related illness and excluding other obvious explanations; and (2) water treatment failure at WTP A. WTP A was closed to facilitate an upgrade. No boil water notice was required as a supplementary supply was available. The upgrade was completed and the incident closed in 2013.

Nosocomial diarrhea outbreak, Chile

Coria P, Urízar C, Alba A, Noemí I, Pino A, Cerva JL. [The water supply of a pediatric hospital as a possible source of an outbreak of diarrhea due to Microsporidium spp. in immunocompromised patients] Rev Chilena Infectol. 2016 Aug;33(4):373-379. [Article in Spanish]

INTRODUCTION: The hospital water supply is a reservoir of a variety of potentially pathogenic microorganisms that can particularly affect children and immunocompromised patients. Potentially pathogenic Microsporidium spp. have been identified in water. Microsporidiosis is an emerging parasitic and opportunistic infection in immunocompromised patients.

OBJECTIVE AND METHOD: to describe an outbreak of nosocomial diarrhea due to Microsporidium, species Encephalitozoon intestinalis.

RESULTS: Seven cases of E. intestinalis associated diarrhea were reported between november 2012 and february 2013, in a unit of immunocompromised patients in L. Calvo Mackenna Children’s Hospital. Microsporidium spp. was found in the hospital water supply and water reservoir tank. Secondary cases were transmitted by contact. Control measures included contact precautions, not to use faucet water for hand washing, bottled water for drinking and water reservoir tank sanitation.

CONCLUSIONS: This research is about a nosocomial outbreak associated with water supply. Water quality in Chilean hospitals is an unresolved issue, especially in immunocompromised patient areas. Compliance of cleaning and disinfection of water supply systems in hospitals must be ensured.

Escherichia coli a Reliable Indicator of Waterborne Illness Potential

Ercumen A, Arnold BF, Naser AM, Unicomb L, Colford JM Jr. Potential sources of bias in the use of Escherichia coli to measure waterborne diarrhea risk in low-income settings. Trop Med Int Health. 2016 Oct 31. doi: 10.1111/tmi.12803

OBJECTIVES: Escherichia coli is the standard water quality indicator for diarrhea risk. Yet the association between E. coli and diarrhea is inconsistent across studies without a systematic assessment of methodological differences behind this variation. Most studies measure water quality cross-sectionally with diarrhea, risking exposure misclassification and reverse causation. Studies use different recall windows for self-reported diarrhea; longer periods increase potential outcome misclassification through misrecall. Control of confounding is inconsistent across studies. Additionally, diarrhea measured in unblinded intervention trials can present courtesy bias. We utilized measurements from a randomized trial of water interventions in Bangladesh to assess how these factors affect the E. coli-diarrhea association.

METHODS: We compared cross-sectional versus prospective measurements of water quality and diarrhea, two- versus seven-day symptom recall periods, estimates with and without controlling for confounding and using measurements from control versus intervention arms of the trial.

RESULTS: In the control arm, two-day diarrhea prevalence, measured prospectively one month after water quality, significantly increased with log10 E. coli (PR=1.50, 1.02-2.20). This association weakened when we used seven-day recall (PR=1.18, 0.88-1.57), cross-sectional measurements of E. coli and diarrhea (PR=1.11, 0.79-1.56) or did not control for confounding (PR=1.20, 0.88-1.62). Including data from intervention arms led to less interpretable associations, potentially due to courtesy bias, effect modification and/or reverse causation.

CONCLUSIONS: By systematically addressing potential sources of bias, our analysis demonstrates a clear relationship between E. coli in drinking water and diarrhea, suggesting that the continued use of E. coli as an indicator of waterborne diarrhea risk is justified.

Factors on Fecal Contamination of Drinking Water, Egypt

Fakhr AE, Gohar MK, Atta AH. Impact of Some Ecological Factors on Fecal Contamination of Drinking Water by Diarrheagenic Antibiotic-Resistant Escherichia coli in Zagazig City, Egypt. International journal of microbiology. 2016;2016:6240703.

Fecal contamination of drinking water is a major health problem which accounts for many cases of diarrhea mainly in infants and foreigners. This contamination is a complex interaction of many parameters. Antibiotic resistance among bacterial isolates complicates the problem. The study was done to identify fecal contamination of drinking water by Diarrheagenic Antibiotic-Resistant Escherichia coli in Zagazig city and to trace reasons for such contamination, three hundred potable water samples were investigated for E. coli existence. Locations of E. coli positive samples were investigated in relation to population density, water source, and type of water pipe. Sixteen E. coli strains were isolated. Antibiotic sensitivity was done and enterotoxigenic, enteropathogenic, and enterohaemorrhagic virulence genes were investigated by PCR. Probability of fecal contamination correlated with higher population density, with increased distance from Zagazig water plant, and with asbestos cement in all isolates. Virulence genes were detected in a rate of 26.27%, 13.13%, 20%, 6.67%, and 33.33% for LT, ST, stx1, stx2, and eae genes, respectively. This relatively high frequency of fecal contamination points towards the high risk of developing diarrhea by antibiotic resistant DEC in low socioeconomic communities particularly with old fashion distribution systems.

Endemic Gastrointestinal Illness Study Equivocal

If I’m reading this correctly the odds ratios are so close to 1 that there is essentially no difference within the limits of this study design and available data, which is contrary to the author’s conclusion.

Tornevi A, Simonsson M, Forsberg B, Säve-Söderbergh M, Toljander J. Efficacy of water treatment processes and endemic gastrointestinal illness – A multi-city study in Sweden. Water Research 2016 Jun 11;102:263-270. doi: 10.1016/j.watres.2016.06.018.

Outbreaks of acute gastrointestinal illnesses (AGI) have been linked to insufficient drinking water treatment on numerous occasions in the industrialized world, but it is largely unknown to what extent public drinking water influences the endemic level of AGI. This paper aimed to examine endemic AGI and the relationship with pathogen elimination efficacy in public drinking water treatment processes. For this reason, time series data of all telephone calls to the Swedish National Healthcare Guide between November 2007 and February 2014 from twenty Swedish cities were obtained. Calls concerning vomiting, diarrhea or abdominal pain (AGI calls) were separated from other concerns (non-AGI calls). Information on which type of microbial barriers each drinking water treatment plant in these cities have been used were obtained, together with the barriers’ theoretical pathogen log reduction efficacy. The total log reduction in the drinking water plants varied between 0.0 and 6.1 units for viruses, 0.0-14.6 units for bacteria and 0.0-7.3 units regarding protozoans. To achieve one general efficacy parameter for each plant, a weighted mean value of the log reductions (WLR) was calculated, with the weights based on how commonly these pathogen groups cause AGI. The WLR in the plants varied between 0.0 and 6.4 units. The effect of different pathogen elimination efficacy on levels of AGI calls relative non-AGI calls was evaluated in regression models, controlling for long term trends, population size, age distribution, and climatological area. Populations receiving drinking water produced with higher total log reduction was associated with a lower relative number of AGI calls. In overall, AGI calls decreased by 4% (OR = 0.96, CI: 0.96-0.97) for each unit increase in the WLR. The findings apply to both groundwater and surface water study sites, but are particularly evident among surface water sites during seasons when viruses are the main cause of AGI. This study proposes that the endemic level of gastroenteritis can indeed be reduced with more advanced treatment processes at many municipal drinking water treatment plants.