Cholera Incidence Research Articles

Clinical, epidemiological, and spatial characteristics of Vibrio parahaemolyticus diarrhea and cholera in the urban slums of Kolkata, India

BackgroundThere is not much information on the differences in clinical, epidemiological and spatial characteristics of diarrhea due to V. cholerae and V. parahaemolyticus from non-coastal areas. We investigated the differences in clinical, epidemiological and spatial characteristics of the two Vibrio species in the urban slums of Kolkata, India.MethodsThe data of a cluster randomized cholera vaccine trial were used. We restricted the analysis to clusters assigned to placebo. Survival analysis of the time to the first episode was used to analyze risk factors for V. parahaemolyticus diarrhea or cholera. A spatial scan test was used to identify high risk areas for cholera and for V. parahaemolyticus diarrhea.ResultsIn total, 54,519 people from the placebo clusters were assembled. The incidence of cholera (1.30/1000/year) was significantly higher than that of V. parahaemolyticus diarrhea (0.63/1000/year). Cholera incidence was inversely related to age, whereas the risk of V. parahaemolyticus diarrhea was age-independent. The seasonality of diarrhea due to the two Vibrio species was similar. Cholera was distinguished by a higher frequency of severe dehydration, and V. parahaemolyticus diarrhea was by abdominal pain. Hindus and those who live in household not using boiled or treated water were more likely to have V. parahaemolyticus diarrhea. Young age, low socioeconomic status, and living closer to a project healthcare facility were associated with an increased risk for cholera. The high risk area for cholera differed from the high risk area for V. parahaemolyticus diarrhea.ConclusionWe report coexistence of the two vibrios in the slums of Kolkata. The two etiologies of diarrhea had a similar seasonality but had distinguishing clinical features. The risk factors and the high risk areas for the two diseases differ from one another suggesting different modes of transmission of these two pathogens.

Effectiveness of an oral cholera vaccine in Zanzibar: findings from a mass vaccination campaign and observational cohort study

Zanzibar, in east Africa, has been severely and repeatedly affected by cholera since 1978. We assessed the effectiveness of oral cholera vaccination in high-risk populations in the archipelago to estimate the indirect (herd) protection conferred by the vaccine and direct vaccine effectiveness. We offered two doses of a killed whole-cell B-subunit cholera vaccine to individuals aged 2 years and older in six rural and urban sites. To estimate vaccine direct protection, we compared the incidence of cholera between recipients and non-recipients using generalised estimating equations with the log link function while controlling for potential confounding variables. To estimate indirect effects, we used a geographic information systems approach and assessed the association between neighbourhood-level vaccine coverage and the risk for cholera in the non-vaccinated residents of that neighbourhood, after controlling for potential confounding variables. This study is registered with ClinicalTrials.gov, number NCT00709410. Of 48,178 individuals eligible to receive the vaccine, 23,921 (50%) received two doses. Between February, 2009, and May, 2010, there was an outbreak of cholera, enabling us to assess vaccine effectiveness. The vaccine conferred 79% (95% CI 47-92) direct protection against cholera in participants who received two doses. Indirect (herd) protection was shown by a decrease in the risk for cholera of non-vaccinated residents within a household's neighbourhood as the vaccine coverage in that neighbourhood increased. Our findings suggest that the oral cholera vaccine offers both direct and indirect (herd) protection in a sub-Saharan African setting. Mass oral cholera immunisation campaigns have the potential to provide not only protection for vaccinated individuals but also for the unvaccinated members of the community and should be strongly considered for wider use. Because this is an internationally-licensed vaccine, we could not undertake a randomised placebo-controlled trial, but the absence of vaccine effectiveness against non-cholera diarrhoea indicates that the noted protection against cholera could not be explained by bias. Bill & Melinda Gates Foundation, Swedish International Development Cooperation Agency, and the South Korean Government.

Integration of Spatial and Social Network Analysis in Disease Transmission Studies

This study presents a case study of how social network and spatial analytical methods can be used simultaneously for disease transmission modeling. The article first reviews strategies employed in previous studies and then offers the example of transmission of two bacterial diarrheal diseases in rural Bangladesh. The goal is to understand how diseases vary socially above and beyond the effects of the local neighborhood context. Patterns of cholera and shigellosis incidence are analyzed in space and within kinship-based social networks in Matlab, Bangladesh. Data include a spatially referenced longitudinal demographic database that consists of approximately 200,000 people and laboratory-confirmed cholera and shigellosis cases from 1983 to 2003. Matrices are created of kinship ties among households using a complete network design and distance matrices are also created to model spatial relationships. Moran's I statistics are calculated to measure clustering within both social and spatial matrices. Combined spatial effects and spatial disturbance models are built to simultaneously analyze spatial and social effects while controlling for local environmental context. Results indicate that cholera and shigellosis always cluster in space and only sometimes within social networks. This suggests that the local environment is most important for understanding transmission of both diseases, although kinship-based social networks also influence their transmission. Simultaneous spatial and social network analysis can help us better understand disease transmission and this study offers several strategies on how.

Model of cholera dissemination using geographic information systems and fuzzy clustering means: Case study, Chabahar, Iran

Cholera is spread by drinking water or eating food that is contaminated by bacteria, and is related to climate changes. Several epidemics have occurred in Iran, the most recent of which was in 2005 with 1133 cases and 12 deaths. This study investigated the incidence of cholera over a 10-year period in Chabahar district, a region with one of the highest incidence rates of cholera in Iran. Descriptive retrospective study on data of patients with Eltor and NAG cholera reported to the Iranian Centre of Disease Control between 1997 and 2006. Data on the prevalence of cholera were gathered through a surveillance system, and a spatial database was developed using geographic information systems (GIS) to describe the relation of spatial and climate variables to cholera incidences. Fuzzy clustering (fuzzy C) method and statistical analysis based on logistic regression were used to develop a model of cholera dissemination. The variables were demographic characteristics, specifications of cholera infection, climate conditions and some geographical parameters. The incidence of cholera was found to be significantly related to higher temperature and humidity, lower precipitation, shorter distance to the eastern border of Iran and local health centres, and longer distance to the district health centre. The fuzzy C means algorithm showed that clusters were geographically distributed in distinct regions. In order to plan, manage and monitor any public health programme, GIS provide ideal platforms for the convergence of disease-specific information, analysis and computation of new data for statistical analysis.

Satellite remote sensing of space–time plankton variability in the Bay of Bengal: Connections to cholera outbreaks

Cholera bacteria exhibit strong association with coastal plankton. Characterization of space–time variability of chlorophyll, a surrogate for plankton abundance, in the northern Bay of Bengal is an essential first step to develop any methodology for predicting cholera outbreaks in the Bengal Delta region using remote sensing. This study quantifies the space–time distribution of chlorophyll, using the data from SeaWiFS, in the Bay of Bengal region using 10years of satellite data. Variability of chlorophyll at daily scale, irrespective of spatial averaging, resembles white noise. At a monthly scale, chlorophyll shows distinct seasonality and chlorophyll values are significantly higher close to the coast than in the offshore regions. At pixel level (9km) on monthly scale, on the other hand, chlorophyll does not exhibit much persistence in time. With increased spatial averaging, temporal persistence of chlorophyll increases and lag 1 autocorrelation stabilizes around 0.60 for 1296km2 or larger areal averages. In contrast to the offshore regions, spatial analyses of chlorophyll suggest that only coastal region has a stable correlation length of 100km. Presence (absence) of correlation length in the coastal (offshore) regions indicate that the two regions may have two separate processes controlling the production of phytoplankton. This study puts a lower limit on space–time averaging of satellite measured plankton at 1296km2 monthly scale to establish relationships with cholera incidence in Bengal Delta.

Hydroclimatology of dual‐peak annual cholera incidence: Insights from a spatially explicit model

Cholera incidence in some regions of the Indian subcontinent may exhibit two annual peaks although the main environmental drivers that have been linked to the disease (e.g., sea surface temperature, zooplankton abundance, river discharge) peak once per year during the summer. An empirical hydroclimatological explanation relating cholera transmission to river flows and to the disease spatial spreading has been recently proposed. We specifically support and substantiate mechanistically such hypothesis by means of a spatially explicit model of cholera transmission. Our framework directly accounts for the role of a model river network in transporting and redistributing cholera bacteria among human communities as well as for spatial and temporal annual fluctuations of river flows. The model is forced by seasonal environmental drivers, namely river flow, temperature and chlorophyll concentration in the coastal environment, a proxy for Vibrio choleraeconcentration. Our results show that these drivers may suffice to generate dual‐peak cholera prevalence patterns for proper combinations of timescales involved in pathogen transport, hydrologic variability and disease unfolding. The model explains the possible occurrence of spatial patterns of cholera incidence characterized by a spring peak confined to coastal areas and a fall peak involving inland regions. Our modeling framework suggests insights on how environmental drivers concert the generation of complex spatiotemporal infections and proposes an explanation for the different cholera patterns (dual or single annual peaks) exhibited by regions that share similar hydroclimatological forcings.

Occurrence of Vibrio cholerae in Municipal and Natural Waters and Incidence of Cholera in Azerbaijan

Cholera, a waterborne disease caused by Vibrio cholerae, is an autochthonous member of the aquatic environment and predominantly reported from developing countries. Technical reports and proceedings were reviewed to determine the relationship between occurrence of V. cholerae in natural waters, including sources of municipal water, and cases of cholera in Azerbaijan. Water samples collected from different environmental sources from 1970 to 1998 were tested for V. cholerae and 0.73% (864/117,893) were positive. The results showed that in April of each year, when the air temperature rose by approximately 5°C, V. cholerae could be isolated. With each increase in air temperature, 6-8 weeks after, impact on cases of cholera was recorded. The incidence of cholera peaked when the air temperature reached >25°C during the month of September. It is concluded that a distinct seasonality in cholera incidence exists in Azerbaijan, with increased occurrence during warmer months.

The costs of climate change: a study of cholera in Tanzania.

Increased temperatures and changes in rainfall patterns as a result of climate change are widely recognized to entail potentially serious consequences for human health, including an increased risk of diarrheal diseases. This study integrates historical data on temperature and rainfall with the burden of disease from cholera in Tanzania and uses socioeconomic data to control for the impacts of general development on the risk of cholera. The results show a significant relationship between temperature and the incidence of cholera. For a 1 degree Celsius temperature increase the initial relative risk of cholera increases by 15 to 29 percent. Based on the modeling results, we project the number and costs of additional cases of cholera that can be attributed to climate change by 2030 in Tanzania for a 1 and 2 degree increase in temperatures, respectively. The total costs of cholera attributable to climate change are shown to be in the range of 0.32 to 1.4 percent of GDP in Tanzania 2030. The results provide useful insights into national-level estimates of the implications of climate change on the health sector and offer information which can feed into both national and international debates on financing and planning adaptation.

Dynamics of Cholera Outbreaks in Great Lakes Region of Africa, 1978–2008

Cholera outbreaks have occurred in Burundi, Rwanda, Democratic Republic of Congo, Tanzania, Uganda, and Kenya almost every year since 1977-1978, when the disease emerged in these countries. We used a multiscale, geographic information system-based approach to assess the link between cholera outbreaks, climate, and environmental variables. We performed time-series analyses and field investigations in the main affected areas. Results showed that cholera greatly increased during El Nino warm events (abnormally warm El Ninos) but decreased or remained stable between these events. Most epidemics occurred in a few hotspots in lakeside areas, where the weekly incidence of cholera varied by season, rainfall, fluctuations of plankton, and fishing activities. During lull periods, persistence of cholera was explained by outbreak dynamics, which suggested a metapopulation pattern, and by endemic foci around the lakes. These links between cholera outbreaks, climate, and lake environments need additional, multidisciplinary study.

Cyclic causality of cholera epidemic manifestations in India

Analysis of the incidence of cholera in India suggests the cyclicity of its manifestations, which is associated with solar activity. The peak numbers of patients have been found to occur an average every 3.1, 5.2, and 10.9 years, which are timed in a phase of the minimum solar activity to the year of its previous minimum and in a phase of its maximum to -2, +1, +2, and +4 years of the maximum.

The Role of Vaccine Coverage within Social Networks in Cholera Vaccine Efficacy

BackgroundTraditional vaccine trial methods have an underlying assumption that the effect of a vaccine is the same throughout the trial area. There are, however, many spatial and behavioral factors that alter the rates of contact among infectious and susceptible individuals and result in different efficacies across a population. We reanalyzed data from a field trial in Bangladesh to ascertain whether there is evidence of indirect protection from cholera vaccines when vaccination rates are high in an individual's social network.MethodsWe analyzed the first year of surveillance data from a placebo-controlled trial of B subunit-killed whole-cell and killed whole-cell-only oral cholera vaccines in children and adult women in Bangladesh. We calculated whether there was an inverse trend for the relation between the level of vaccine coverage in an individual's social network and the incidence of cholera in individual vaccine recipients or placebo recipients after controlling for potential confounding variables.ResultsUsing bari-level social network ties, we found incidence rates of cholera among placebo recipients were inversely related to levels of vaccine coverage (5.28 cases per 1000 in the lowest quintile vs 3.27 cases per 1000 in the highest quintile; p = 0.037 for trend). Receipt of vaccine by an individual and the level of vaccine coverage of the individual's social network were independently related to a reduced risk of cholera.ConclusionsFindings indicate that progressively higher levels of vaccine coverage in bari-level social networks can lead to increasing levels of indirect protection of non-vaccinated individuals and could also lead to progressively higher levels of total protection of vaccine recipients.

Role of Zooplankton Diversity in Vibrio cholerae Population Dynamics and in the Incidence of Cholera in the Bangladesh Sundarbans

Vibrio cholerae, a bacterium autochthonous to the aquatic environment, is the causative agent of cholera, a severe watery, life-threatening diarrheal disease occurring predominantly in developing countries. V. cholerae, including both serogroups O1 and O139, is found in association with crustacean zooplankton, mainly copepods, and notably in ponds, rivers, and estuarine systems globally. The incidence of cholera and occurrence of pathogenic V. cholerae strains with zooplankton were studied in two areas of Bangladesh: Bakerganj and Mathbaria. Chitinous zooplankton communities of several bodies of water were analyzed in order to understand the interaction of the zooplankton population composition with the population dynamics of pathogenic V. cholerae and incidence of cholera. Two dominant zooplankton groups were found to be consistently associated with detection of V. cholerae and/or occurrence of cholera cases, namely, rotifers and cladocerans, in addition to copepods. Local differences indicate there are subtle ecological factors that can influence interactions between V. cholerae, its plankton hosts, and the incidence of cholera.

Climate Variability and the Outbreaks of Cholera in Zanzibar, East Africa: A Time Series Analysis

Global cholera incidence is increasing, particularly in sub-Saharan Africa. We examined the impact of climate and ocean environmental variability on cholera outbreaks, and developed a forecasting model for outbreaks in Zanzibar. Routine cholera surveillance reports between 1997 and 2006 were correlated with remotely and locally sensed environmental data. A seasonal autoregressive integrated moving average (SARIMA) model determined the impact of climate and environmental variability on cholera. The SARIMA model shows temporal clustering of cholera. A 1°C increase in temperature at 4 months lag resulted in a 2-fold increase of cholera cases, and an increase of 200 mm of rainfall at 2 months lag resulted in a 1.6-fold increase of cholera cases. Temperature and rainfall interaction yielded a significantly positive association (P < 0.04) with cholera at a 1-month lag. These results may be applied to forecast cholera outbreaks, and guide public health resources in controlling cholera in Zanzibar.

Hydroclimatic influences on seasonal and spatial cholera transmission cycles: Implications for public health intervention in the Bengal Delta

Cholera remains a major public health threat in many developing countries around the world. The striking seasonality and annual recurrence of this infectious disease in endemic areas remain of considerable interest to scientists and public health workers. Despite major advances in the ecological and microbiological understanding of Vibrio cholerae, the causative agent of the disease, the role of underlying large‐scale hydroclimatic processes in propagating the disease for different seasons and spatial locations is not well understood. Here we show that the cholera outbreaks in the Bengal Delta region are propagated from the coastal to the inland areas and from spring to fall by two distinctly different transmission cycles, premonsoon and postmonsoon, influenced by coastal and terrestrial hydroclimatic processes, respectively. A coupled analysis of the regional hydroclimate and cholera incidence reveals a strong association of the space‐time variability of incidence peaks with seasonal processes and extreme climatic events. We explain how the asymmetric seasonal hydroclimatology affects regional cholera dynamics by providing a coastal growth environment for bacteria in spring, while propagating the disease to fall by monsoon flooding. Our findings may serve as the basis for “climate‐informed” early warnings and for prompting effective means for intervention and preempting epidemic cholera outbreaks in vulnerable regions.

Alcohol and cholera

‘Fear and humour in the art of cholera’ was stimulating. It stated ‘“cholera brandy” was one of the many unproven cures or preventive measures against the disease’.1 In 1832, the Inverness Board of Health had advocated ‘great moderation in the use of fermented and spirituous liquors’. Recently, we investigated this matter and tested the effects of alcohol on the survival of Vibrio cholerae in gin, red wine and ethanol.2 We found V. cholerae did not survive in 20% gin at 1 hour, 18.75% gin at 6 hours and 15% gin at 26 hours. Similar survival times were found with the equivalent concentrations of ethanol.3 The results were much more dramatic with red wine, V. cholerae did not survive in 6.25% wine at 30 min;2 its bactericidal effect may be attributable to polyphenols.4 Nevertheless, in 1832 the incidence of cholera was seen to be higher in the heavy drinker than among the general population.5 Some saw this higher incidence as Divine retribution.5 However, the scientific explanation, unknown in 1832, is that the heavy drinker may have reduced gastric acidity6 and the infectious dose of V. cholerae will be lower than for those with normal chlorhydria. Conversely, the moderate consumption of wine and beer stimulate the production of gastric acid and may have a protective effect against cholera.6 Fear and humour may be helped by alcohol but it can also reduce infection with cholera.

The phenotypic and molecular biological characteristics of Vibrio cholerae El Tor strains isolated from environmental water objects in Rostov-on-Don in 2003-2008

The pheno- and genotypic properties of Vibrio cholerae El Tor cultures identified during monitoring for V. cholerae in the aquatic ecosystems of Rostov-on-Don in the period 2003-2008 were studied in the extended range. In addition to known laboratory diagnostic techniques for cholera, the authors used a volume agglomeration test with antilipase diagnosticum, as well as polymerase chain reaction using specific primers to detect 30 nucleotide sequences of the genes associated with V. cholerae pathogenicity. The range of pheno- and genotypic characteristics of study V. cholerae O1 cultures was extended. There was evidence for the volume agglomeration test with a polymerase antilipase agent as a complementary test for toxicogenicity. The Vibrio cholerae O1 strains isolated from the aquatic environment were shown to confer a real and potential risk in the low cholera incidence area of Rostov-on-Don. The findings may be used to improve methodic approaches to monitoring environmental objects for Vibrio cholerae in the optimization of epidemiological surveillance of cholera at the regional level.

Strategic framework for cholera prevention and control in Chengdu: construction and effectiveness evaluation

To construct an operable strategic framework for cholera prevention and control which mobilized the advantages of local resources and adapted to social developments in Chengdu, and to evaluate its application effects. (1) After analyzing the local epidemic data of cholera in Chengdu from 1994 to 2004, we determined the main problems of cholera prevention and control works as well as the efficiency and deficiency of employed measures, and then formed a basic strategic framework. (2) After 55 invited experts preliminarily scored the strategic framework, we selected 72 specific measures to establish a measure entry database, and then the importance and operability of each measure were scored by 17 core experts. (3) Finally, the effectiveness of this strategic framework was evaluated according to the analyzing results of infection control, health education and etiological monitoring. (1) The framework took government leadership as main scenario and the informatization as subordination scenario. Meanwhile, it focused on three points: the improvement of social environment, the completion of system and mechanisms for monitoring and early warning, and the enhancement of CDC response to public health emergencies. Total importance score and operability score of 35 specific measures included in this framework was 4.20 ± 0.86 and 4.09 ± 0.87, respectively. (2) Chengdu had maintained zero cholera incidence for five consecutive years from 2005 to 2009 since it gradually began to implement the strategic framework in 2002. There were 19 positive cholera cases detected by etiological monitoring and all of them were seafood or fishery products including soft-shelled turtles, silver carps and bullfrogs. The coverage rate and qualification rate of the training for grassroots cadres, grassroots medical workers, mobile cooks and their assistants was 98.14% (198 452/202 220) and 98.17% (194 820/198 452) in average, respectively. The qualification rate of the training for employees in food industry was over 96.00% (912 470/950 489). The average awareness rate of cholera prevention and cure knowledge in rural residents, grassroots cadres, grassroots medical workers, mobile cooks and their assistants was 93.87% (1653/1761) and the average formation rate of good hygiene habits was 70.58% (1243/1761). A strategic framework suitable for cholera prevention and control in Chengdu has been successfully established in this study. The incidence rate of cholera has maintained zero in Chengdu for five consecutive years under incessant threatening conditions such as the occurrence of cholera cases from time to time in its surrounding areas and the continuous existence of Bacillus comma in seafood or fishery products that entered local markets. Therefore, it demonstrated a good application effects.

Clonal transmission, dual peak, and off-season cholera in Bangladesh

Vibrio cholerae is an estuarine bacterium associated with a single peak of cholera (March–May) in coastal villages of Bangladesh. For an unknown reason, however, cholera occurs in a unique dual peak (March–May and September–November) pattern in the city of Dhaka that is bordered by a heavily polluted freshwater river system and flood embankment. In August 2007, extreme flooding was accompanied by an unusually severe diarrhea outbreak in Dhaka that resulted in a record high illness. This study was aimed to understand the unusual outbreak and if it was related to the circulation of a new V. cholerae clone. Nineteen V. cholerae isolated during the peak of the 2007 outbreak were subjected to extensive phenotypic and molecular analyses, including multi-locus genetic screening by polymerase chain reaction (PCR), sequence-typing of the ctxB gene, and pulsed-field gel electrophoresis (PFGE). Factors associated with the unusual incidence of cholera were determined and analysis of the disease severity was done. Overall, microbiological and molecular data confirmed that the hypervirulent V. cholerae was O1 biotype El Tor (ET) that possessed cholera toxin (CT) of the classical biotype. The PFGE (NotI) and dendrogram clustering confirmed that the strains were clonal and related to the pre-2007 variant ET from Dhaka and Matlab and resembled one of two distinct clones of the variant ET confirmed to be present in the estuarine ecosystem of Bangladesh. Results of the analyses of both diarrheal case data for three consecutive years (2006–2008) and regional hydroclimatology over three decades (1980–2009) clearly indicate that the pattern of cholera occurring in Dhaka, and not seen at other endemic sites, was associated with flood waters transmitting the infectious clone circulating via the fecal-oral route during and between the dual seasonal cholera peaks in Dhaka. Circular river systems and flood embankment likely facilitate transmission of infectious V. cholerae throughout the year that leads to both sudden and off-season outbreaks in the densely populated urban ecosystem of Dhaka. Clonal recycling of hybrid El Tor with increasing virulence in a changing climate and in a region with a growing urban population represents a serious public health concern for Bangladesh.

The Indian Ocean Dipole and Cholera Incidence in Bangladesh: A Time-Series Analysis

BackgroundIt has been reported that the El Niño–Southern Oscillation (ENSO) influences the interannual variation of endemic cholera in Bangladesh. There is increased interest in the influence of the Indian Ocean dipole (IOD), a climate mode of coupled ocean–atmosphere variability, on regional ocean climate in the Bay of Bengal and on Indian monsoon rainfall.ObjectivesWe explored the relationship between the IOD and the number of cholera patients in Bangladesh, controlling for the effects of ENSO.MethodsTime-series regression was performed. Negative binomial models were used to estimate associations between the monthly number of hospital visits for cholera in Dhaka and Matlab (1993–2007) and the dipole mode index (DMI) controlling for ENSO index [NINO3, a measure of the average sea surface temperature (SST) in the Niño 3 region], seasonal, and interannual variations. Associations between cholera cases and SST and sea surface height (SSH) of the northern Bay of Bengal were also examined.ResultsA 0.1-unit increase in average DMI during the current month through 3 months before was associated with an increase in cholera incidence of 2.6% [(95% confidence interval (CI), 0.0–5.2; p = 0.05] in Dhaka and 6.9% (95% CI, 3.2–10.8; p < 0.01) in Matlab. Cholera incidence in Dhaka increased by 2.4% (95% CI, 0.0–5.0; p = 0.06) after a 0.1-unit decrease in DMI 4–7 months before. Hospital visits for cholera in both areas were positively associated with SST 0–3 months before, after adjusting for SSH (p < 0.01).ConclusionsThese findings suggest that both negative and positive dipole events are associated with an increased incidence of cholera in Bangladesh with varying time lags.

Novel Approaches Address New Challenges

Disinfection is one of the most critical components in the multiple barrier approach to the protection of public health. Since the 1800s when Dr. John Snow made the connection between the incidence of cholera and water coming from the Broad Street pump, the practice of disinfection has evolved into a sophisticated process that incorporates many methods. As this month's articles show, novel treatments continue to be developed as new challenges arise.