Temperature is considered as the major factor determining virus inactivation in the environment. Food industries, therefore, widely apply temperature as virus inactivating parameter. This review ...encompasses an overview of viral inactivation and virus genome degradation data from published literature as well as a statistical analysis and the development of empirical formulae to predict virus inactivation. A total of 658 data (time to obtain a first log10 reduction) were collected from 76 published studies with 563 data on virus infectivity and 95 data on genome degradation. Linear model fitting was applied to analyse the effects of temperature, virus species, detection method (cell culture or molecular methods), matrix (simple or complex) and temperature category (<50 and ≥50°C). As expected, virus inactivation was found to be faster at temperatures ≥50°C than at temperatures <50°C, but there was also a significant temperature–matrix effect. Virus inactivation appeared to occur faster in complex than in simple matrices. In general, bacteriophages PRD1 and PhiX174 appeared to be highly persistent whatever the matrix or the temperature, which makes them useful indicators for virus inactivation studies. The virus genome was shown to be more resistant than infectious virus. Simple empirical formulas were developed that can be used to predict virus inactivation and genome degradation for untested temperatures, time points or even virus strains.
Flooding and heavy rainfall have been associated with waterborne infectious disease outbreaks, however, it is unclear to which extent they pose a risk for public health. Here, risks of infection from ...exposure to urban floodwater were assessed using quantitative microbial risk assessment (QMRA). To that aim, urban floodwaters were sampled in the Netherlands during 23 events in 2011 and 2012. The water contained Campylobacter jejuni (prevalence 61%, range 14- >103 MPN/l), Giardia spp. (35%, 0.1–142 cysts/l), Cryptosporidium (30%, 0.1–9.8 oocysts/l), noroviruses (29%, 102–104 pdu/l) and enteroviruses (35%, 103–104 pdu/l). Exposure data collected by questionnaire, revealed that children swallowed 1.7 ml (mean, 95% Confidence Interval 0–4.6 ml) per exposure event and adults swallowed 0.016 ml (mean, 95% CI 0–0.068 ml) due to hand-mouth contact. The mean risk of infection per event for children, who were exposed to floodwater originating from combined sewers, storm sewers and rainfall generated surface runoff was 33%, 23% and 3.5%, respectively, and for adults it was 3.9%, 0.58% and 0.039%. The annual risk of infection was calculated to compare flooding from different urban drainage systems. An exposure frequency of once every 10 years to flooding originating from combined sewers resulted in an annual risk of infection of 8%, which was equal to the risk of infection of flooding originating from rainfall generated surface runoff 2.3 times per year. However, these annual infection risks will increase with a higher frequency of urban flooding due to heavy rainfall as foreseen in climate change projections.
•Urban flooding was measured for enteric pathogens to assess risks for public health.•Health risks were quantified for flooding of different urban drainage systems.•The annual risk of infection for flooding originating from combined sewers was 8%.
Escherichia coli and thermotolerant coliforms are of major importance as indicators of fecal contamination of water. Due to its negative surface charge and relatively low die-off or inactivation rate ...coefficient,
E. coli is able to travel long distances underground and is therefore also a useful indicator of fecal contamination of groundwater. In this review, the major processes known to determine the underground transport of
E. coli (attachment, straining and inactivation) are evaluated. The single collector contact efficiency (SCCE),
η
0
, one of two parameters commonly used to assess the importance of attachment, can be quantified for
E. coli using classical colloid filtration theory. The sticking efficiency,
α, the second parameter frequently used in determining attachment, varies widely (from 0.003 to almost 1) and mainly depends on charge differences between the surface of the collector and
E. coli. Straining can be quantified from geometrical considerations; it is proposed to employ a so-called straining correction parameter,
α
str
. Sticking efficiencies determined from field experiments were lower than those determined under laboratory conditions. We hypothesize that this is due to preferential flow mechanisms,
E. coli population heterogeneity, and/or the presence of organic and inorganic compounds in wastewater possibly affecting bacterial attachment characteristics. Of equal importance is the inactivation or die-off of
E. coli that is affected by factors like type of bacterial strain, temperature, predation, antagonism, light, soil type, pH, toxic substances, and dissolved oxygen. Modeling transport of
E. coli can be separated into three steps: (1) attachment rate coefficients and straining rate coefficients can be calculated from Darcy flow velocity fields or pore water flow velocity fields, calculated SCCE fields, realistic sticking efficiency values and straining correction parameters, (2) together with the inactivation rate coefficient, total rate coefficient fields can be generated, and (3) used as input for modeling the transport of
E. coli in existing contaminant transport codes. Areas of future research are manifold and include the effects of typical wastewater characteristics, including high concentrations of organic compounds, on the transport of
E. coli and thermotolerant coliforms, and the upscaling of experiments to represent typical field conditions, possibly including preferential flow mechanisms and the aspect of population heterogeneity of
E. coli.
Pollutants, brought into a swimming pool by bathers, will react with chlorine to form disinfection by-products (DBPs). Some of these DBPs are found to be respiratory and ocular irritant and might be ...associated with asthma, or might even be carcinogenic. As DBPs in swimming pools are formed from bather-shed-pollutants, a reduction of these pollutants will lead to a reduction of DBPs. Until now, however, the release of pollutants by bathers has not been studied in detail. The study described in this paper focuses on the release of these pollutants, further called anthropogenic pollutants. The objective was to define and quantify the initial anthropogenic pollutants, by using a standardised shower cabin and a standardised showering protocol in laboratory time-series experiments and on-site experiments in swimming pools. The time-series experiments resulted in a definition of the initial anthropogenic pollutant release: the amount of pollutants released from a person in a standardised shower cabin during the first 60 s of showering. The data from the time-series experiments were used to create a model of pollutant release. The model can be used to predict the initial anthropogenic pollutant release as well as the effects of showering. On-site experiments were performed at four different swimming pools, including one outdoor pool. Results of these on-site showering experiments correspond with the time-series and model outcomes. Anthropogenic pollutant release (both chemical and microbiological) in swimming pool water can be reduced by pre-swim showering, very likely resulting in decreased DBPs formation and chlorine demand.
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► Shower experiments were performed to determine pollutant release by bathers. ► Time-series data were used to create a model of the pollutant release in a shower. ► The model was validated at four swimming pool locations. ► Pre-swim showering reduces anthropogenic pollutants in swimming pool water.
To elucidate the parameters determining the transport of
Escherichia coli in aquifers, the attachment of
E. coli in low concentrations to column sediments was investigated. The sediments comprised ...0.18–0.50
mm quartz sand, grains coated with goethite, calcite grains or grains of activated carbon (AC), in varying fractions (
λ
=
0
, 0.05, 0.1, 0.2, 0.4, 0.7, 1.0) and all of similar diameter to the quartz sand. The weighted sum of favourable and unfavourable sticking efficiencies (
α
total
) showed that upon increasing the fraction of favourable mineral grains (
λ
) there was an initial rapid increase, which then slowed down. This was most pronounced in the AC experiments, followed by the calcite experiments and then the goethite experiments. We ascribe this non-linear relation to surface charge and hydrophobic heterogeneity of the
E. coli population.
Since the transmission of pathogenic viruses via water is indistinguishable from the transmission via other routes and since the levels in drinking water, although significant for health, may be too ...low for detection, quantitative viral risk assessment is a useful tool for assessing disease risk due to consumption of drinking water. Quantitative viral risk assessment requires information concerning the ability of viruses detected in drinking water to infect their host. To obtain insight into the infectivity of viruses in relation to the presence of virus genomes, inactivation of three different enteroviruses in artificial ground and surface waters under different controlled pH, temperature, and salt conditions was studied by using both PCR and cell culture over time. In salt-peptone medium, the estimated ratio of RNA genomes to infectious poliovirus 1 in freshly prepared suspensions was about 10⁰. At 4°C this ratio was 10³ after 600 days, and at 22°C it was 10⁴ after 200 days. For poliovirus 1 and 2 the RNA/infectious virus ratio was higher in artificial groundwater than in artificial surface water, but this was not the case for coxsackievirus B4. When molecular detection is used for virus enumeration, it is important that the fraction of infectious virus (based on all virus genomes detected) decays with time, especially at temperatures near 22°C.
The water in the canals and some recreational lakes in Amsterdam is microbiologically contaminated through the discharge of raw sewage from houseboats, sewage effluent, and dog and bird feces. ...Exposure to these waters may have negative health effects. During two successive 1-year study periods, the water quality in two canals (2003 to 2004) and five recreational lakes (2004 to 2005) in Amsterdam was tested with regard to the presence of fecal indicators and waterborne pathogens. According to Bathing Water Directive 2006/7/EC, based on Escherichia coli and intestinal enterococcus counts, water quality in the canals was poor but was classified as excellent in the recreational lakes. Campylobacter, Salmonella, Cryptosporidium, and Giardia were detected in the canals, as was rotavirus, norovirus, and enterovirus RNA. Low numbers of Cryptosporidium oocysts and Giardia cysts were detected in the recreational lakes, despite compliance with European bathing water legislation. The estimated risk of infection with Cryptosporidium and Giardia per exposure event ranged from 0.0002 to 0.007% and 0.04 to 0.2%, respectively, for occupational divers professionally exposed to canal water. The estimated risk of infection at exposure to incidental peak concentrations of Cryptosporidium and Giardia may be up to 0.01% and 1%, respectively, for people who accidentally swallow larger volumes of the canal water than the divers. Low levels of viable waterborne pathogens, such as Cryptosporidium and Giardia, pose a possible health risk from occupational, accidental, and recreational exposure to surface waters in Amsterdam.
Pneumatic dilation and laparoscopic Heller's myotomy (LHM) are established treatments for idiopathic achalasia. Peroral endoscopic myotomy (POEM) is a less invasive therapy with promising early study ...results.
In a multicenter, randomized trial, we compared POEM with LHM plus Dor's fundoplication in patients with symptomatic achalasia. The primary end point was clinical success, defined as an Eckardt symptom score of 3 or less (range, 0 to 12, with higher scores indicating more severe symptoms of achalasia) without the use of additional treatments, at the 2-year follow-up; a noninferiority margin of -12.5 percentage points was used in the primary analysis. Secondary end points included adverse events, esophageal function, Gastrointestinal Quality of Life Index score (range, 0 to 144, with higher scores indicating better function), and gastroesophageal reflux.
A total of 221 patients were randomly assigned to undergo either POEM (112 patients) or LHM plus Dor's fundoplication (109 patients). Clinical success at the 2-year follow-up was observed in 83.0% of patients in the POEM group and 81.7% of patients in the LHM group (difference, 1.4 percentage points; 95% confidence interval CI, -8.7 to 11.4; P = 0.007 for noninferiority). Serious adverse events occurred in 2.7% of patients in the POEM group and 7.3% of patients in the LHM group. Improvement in esophageal function from baseline to 24 months, as assessed by measurement of the integrated relaxation pressure of the lower esophageal sphincter, did not differ significantly between the treatment groups (difference, -0.75 mm Hg; 95% CI, -2.26 to 0.76), nor did improvement in the score on the Gastrointestinal Quality of Life Index (difference, 0.14 points; 95% CI, -4.01 to 4.28). At 3 months, 57% of patients in the POEM group and 20% of patients in the LHM group had reflux esophagitis, as assessed by endoscopy; at 24 months, the corresponding percentages were 44% and 29%.
In this randomized trial, POEM was noninferior to LHM plus Dor's fundoplication in controlling symptoms of achalasia at 2 years. Gastroesophageal reflux was more common among patients who underwent POEM than among those who underwent LHM. (Funded by the European Clinical Research Infrastructure Network and others; ClinicalTrials.gov number, NCT01601678.).
The Work Group for Evaluation and Implementation of Simulators and Skills Training Programmes is a newly formed sub-group of the European Association of Endoscopic Surgeons (EAES). This work group ...undertook a review of validation evidence for surgical simulators and the resulting consensus is presented in this article. Using clinical guidelines criteria, the evidence for validation for six different simulators was rated and subsequently translated to a level of recommendation for each system. The simulators could be divided into two basic types; systems for laparoscopic general surgery and flexible gastrointestinal endoscopy. Selection of simulators for inclusion in this consensus was based on their availability and relatively widespread usage as of July 2004. Whilst level 2 recommendations were achieved for a few systems, it was clear that there was an overall lack of published validation studies with rigorous experimental methodology. Since the consensus meeting, there have been a number of new articles, system upgrades and new devices available. The work group intends to update these consensus guidelines on a regular basis, with the resulting article available on the EAES website (http://www.eaes-eur.org ).
Riverbank filtration is an effective process for removing pathogenic viruses from river water. Despite indications that changing hydraulic conditions during floods can affect the efficacy of ...riverbank filtration to remove viruses, the impact on advection and dispersion of viruses in the riverbank is not well understood. We investigated the effects of fluctuations in river water level on virus transport during riverbank filtration, considering 3-D transient groundwater flow and virus transport. Using constant removal rates from published field experiments with bacteriophages, removal of viruses with distance from the riverbank was simulated for coarse gravel, fine gravel and fine sandy gravel.
Our simulations showed that, in comparison with steady flow conditions, fluctuations in river water level cause viruses to be transported further at higher concentrations into the riverbank. A 1–5m increase in river water levels led to a 2- to 4-log (log10 reduction in concentration relative to the initial concentration in the river) increase in virus concentration and to up to 30 % shorter travel times. For particular cases during the receding flood, changing groundwater flow conditions caused that pristine groundwater was carried from further inland and that simulated virus concentrations were more diluted in groundwater. Our study suggests that the adverse effect of water level fluctuations on virus transport should be considered in the simulation of safe setback distances for drinking water supplies.
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