Kwesiga B, Pande G, Ario AR, Tumwesigye NM, Matovu JKB, Zhu BP. A prolonged, community-wide cholera outbreak associated with drinking water contaminated by sewage in Kasese District, western Uganda. BMC Public Health. 2017 Jul 18;18(1):30. doi: 10.1186/s12889-017-4589-9.
BACKGROUND: In May 2015, a cholera outbreak that had lasted 3 months and infected over 100 people was reported in Kasese District, Uganda, where multiple cholera outbreaks had occurred previously. We conducted an investigation to identify the mode of transmission to guide control measures.
METHODS: We defined a suspected case as onset of acute watery diarrhoea from 1 February 2015 onwards in a Kasese resident. A confirmed case was a suspected case with Vibrio cholerae O1 El Tor, serotype Inaba cultured from a stool sample. We reviewed medical records to find cases. We conducted a case-control study to compare exposures among confirmed case-persons and asymptomatic controls, matched by village and age-group. We conducted environmental assessments. We tested water samples from the most affected area for total coliforms using the Most Probable Number (MPN) method.
RESULTS: We identified 183 suspected cases including 61 confirmed cases of Vibrio cholerae 01; serotype Inaba, with onset between February and July 2015. 2 case-persons died of cholera. The outbreak occurred in 80 villages and affected all age groups; the highest attack rate occurred in the 5-14 year age group (4.1/10,000). The outbreak started in Bwera Sub-County bordering the Democratic Republic of Congo and spread eastward through sustained community transmission. The first case-persons were involved in cross-border trading. The case-control study, which involved 49 confirmed cases and 201 controls, showed that 94% (46/49) of case-persons compared with 79% (160/201) of control-persons drank water without boiling or treatment (ORM-H=4.8, 95% CI: 1.3-18). Water collected from the two main sources, i.e., public pipes (consumed by 39% of case-persons and 38% of control-persons) or streams (consumed by 29% of case-persons and 24% control-persons) had high coliform counts, a marker of faecal contamination. Environmental assessment revealed evidence of open defecation along the streams. No food items were significantly associated with illness.
CONCLUSIONS: This prolonged, community-wide cholera outbreak was associated with drinking water contaminated by faecal matter and cross-border trading. We recommended rigorous disposal of patients’ faeces, chlorination of piped water, and boiling or treatment of drinking water. The outbreak stopped 6 weeks after these recommendations were implemented.
Spencer R. Hall, Alan J. Tessier, Meghan A. Duffy, Marianne Huebner, and Carla E. Cceres. Warmer Does Not Have to Mean Sicker: Temperature and Predators can Jointly Drive Timing of Epidemics. Ecology, 87(7), 2006, pp. 1684-1695
Ecologists and epidemiologists worry that global warming will increase disease prevalence. These fears arise because several direct and indirect mechanisms link warming to disease, and because parasite outbreaks are increasing in many taxa. However, this outcome is not a foregone conclusion, as physiological and community-interaction-based mechanisms may inhibit epidemics at warmer temperatures. Here, we explore this thermal-community ecology-based mechanism, centering on fish predators that selectively prey upon Daphnia infected with a fungal parasite. We used an interplay between a simple model built around this system’s biology and laboratory experiments designed to parameterize the model. Through this data-model interaction, we found that a given density of predators can inhibit epidemics as temperatures rise when thermal physiology of the predator scales more steeply than that of the host. This case is met in our nsh-Daphnia-iungus system. Furthermore, the combination of steeply scaling parasite physiology and predation-induced mortality can inhibit epidemics at lower temperatures. This effect may terminate fungal epidemics of Daphnia as lakes cool in autumn. Thus, predation and physiology could constrain epidemics to intermediate temperatures (a pattern that we see in our system). More generally, these results accentuate the possibility that warmer temperatures might actually enhance predator control of parasites.
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.
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.
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.
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.
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.