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Situation analysis and epidemiology of infectious disease transmission: a South-East Asian regional perspective.

This paper analyses the situation in countries comprising the WHO South-East Asia Region with respect to water supply and sanitation services, hygiene and the epidemiology of related infectious diseases. Recently, published data from the WHO/UNICEF Global Water Supply and Sanitation Assessment 2000 report was reviewed to depict the situation with respect to consumers' access to improved water supply and sanitation services. It was shown that access to improved drinking water supplies is among the lowest in the world, and that sanitation coverage in this region is below all others. The paper also reviews selected surveys of hygiene behaviours in several countries of the region. Associations are suggested between access to services, hygienic practices and specific infectious diseases. The need is acknowledged to improve the evidence base on linkages between infectious diseases and water, sanitation and hygiene, and specific recommendations are made in this regard. There is a need now and for the foreseeable future to promote low-cost household-level interventions, including behaviour change strategies, that mitigate the health consequences of the current situation with respect to water supply, sanitation and hygiene. The role of health authorities in meeting this challenge, and as advocates for accelerating development of the water and sanitation sector, is highlighted.

Asia, Southeastern↗

Providing clean water, keeping water clean: an integrated approach.

Millions of people, most of whom are children in developing countries, die of basic hygiene-related diseases every year. Interventions in hygiene, sanitation and water supply have been shown to control disease burden. Universal access to improved water sources and basic sanitation remains elusive but is an important long-term goal. Studies have shown that improving the microbiological quality of household water by on-site or point-of-use treatment and safe storage in improved vessels reduces diarrhoeal and other waterborne diseases in communities and households of developing and developed countries. The extent to which improving drinking water quality at the household level reduces diarrhoeal disease probably depends on a variety of technology-related and site-specific environmental and demographic factors that require further investigation, characterisation and analyses.

Chlorine Compounds↗

Coping with hygiene in South Africa, a water scarce country.

The burden of infectious diseases may be reduced by adopting effective infection control measures. Some of these are dependent on the provision of adequate and safe water supplies for maintenance of basic standards of personal, domestic and healthcare hygiene. Consequences of scarce, and sometimes unsafe, waters supplies in South Africa are highlighted with reference to healthcare-associated infections, community acquired infectious intestinal diseases and domestic practices as infection sources. Availability of water in more than 67% of South African municipal hospitals and primary health care facilities (delivered by water tanker in 12.5% of satellite clinics, 5% from river or dam sources, 12.4% relying on rainwater) does not necessarily guarantee that it's quality is safe for utilisation. In the Northern Province and Mpumalanga, water needs to be purified prior to usage in 14.4 and 33% of satellite clinics respectively. Simple, low maintenance and low-cost interventions to maximise use and safety of limited water resources may be implemented: micro-organism (S. dysenteriae) inactivation by direct UV-exposure in sunlight abundant environments, water purification by filtration mechanisms and making use of iron pots in the community for pasteurisation, decontamination and boiling procedures. Education is paramount in promoting healthy domestic food handling practices, changing cultural perceptions of hygiene, hand-washing technique and mechanisms of domestic environmental decontamination. Water provision cannot be separated from other inter-related factors such as sanitation. Although the present government has taken initiatives to reduce the number of people not having access to water by 50% in 2002, provision of sanitation has been slower (>38% inadequate sanitation in 2002). Adoption of integrated environmental management approaches in conjunction with community participation (WASH Campaign--2002), by the government, aims to address the sanitation problems.

Communicable Disease Control↗

Generating high quality impervious cover data.

Nonpoint source pollution (NPS) from urban or suburban areas is rapidly increasing as the population increases in the United States. Research in recent years has consistently shown a strong relationship between the percentage of impervious cover in a drainage basin and the health of the receiving stream. In this paper, we quantify the amount of impervious cover within 56 14-digit hydrologic unit codes (HUCs) in Frederick County, Maryland, USA. This test data set will help in the development of region-wide impervious cover estimation methodologies. The software, sampling and analysis systems were developed to yield accurate and reproducible results. Digital orthophoto quarter quadrangles (DOQQ) from the U.S. Geological Survey were chosen as the basic media for the analysis. Ground features were identified and categorized by human analysts with the help of Geographic Information System (GIS) software and a prototype "cover tool" extension.

Data Collection↗

A task-based statistical model of a worker's exposure distribution: Part I--Description of the model.

The authors present a task-based model to describe a single worker's exposures to a single airborne chemical toxicant. The model accounts for variability in short-term time-weighted average (TWA) exposure values within a task, and for variability in arithmetic mean exposure levels between tasks. For a given workday, the 8-hour TWA value is equated with the sample mean of an appropriate number of short-term TWAs arising from stratified random sampling of short-term TWAs with proportional allocation by task. The model accounts for autocorrelation in the stochastic process that generates successive short-term TWA values. Due to the underlying random process, a given type of workday with regard to the set of task times has an associated distribution of 8-hour TWA values; the variance of this distribution increases with increasing autocorrelation in the time series of short-term TWAs. A worker's total distribution of 8-hour TWAs is a mixture of these day-specific distributions weighted by the relative frequency of each type of workday; the variance of the total distribution increases with greater day-to-day variability in the array of task times.

Air Pollutants, Occupational↗

A task-based statistical model of a worker's exposure distribution: Part II--Application to sampling strategy.

A task-based statistical model of a worker's exposure distribution for an airborne chemical toxicant is applied to estimating the long-term average exposure level, mu. The precision in estimation is represented by the variance of the sample estimator, denoted by Var[mu]. A traditional sampling strategy consists of integratively measuring the 8-hr time-weighted average exposure level on randomly selected workdays, and computing the sample mean; this strategy is termed "simple one-stage cluster sampling," where each 8-hr workday is a cluster of thirty-two 15-min periods. Three alternative strategies involving measurements of 15-min TWAs are examined: simple random sampling of 15-min periods, and stratified random sampling of 15-min periods with proportional allocation by task, and with optimum allocation by task. All four survey designs provide unbiased estimates of mu. However, for a fixed cost, the stratified sampling designs may provide a lower Var[mu] than simple one-stage cluster sampling for less work time monitored.

Air Pollutants, Occupational↗

Yellow is mellow.

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California↗

Bacterial contamination associated with electronic faucets: a new risk for healthcare facilities.

OBJECTIVE: To investigate the safety of the hospital water supply following a major flood. DESIGN: Surveillance was conducted of the hospital water supply as it entered the hospital and at randomly selected water faucets throughout the facility. SETTING: A newly constructed surgical critical-care unit in a 265-bed community hospital that had to be evacuated and was out of operation for 6 weeks following a major flood of the city. METHODS: Random water samples throughout the facility were analyzed for heterotrophic plate counts (HPCs), chlorine, and coliforms utilizing standard methods. RESULTS: Water samples entering the hospital met appropriate standards, indicating the city water distribution system was not contaminated. Of 169 faucets tested, 13 (22%) of 59 electronic faucets exceeded the HPC threshold, and 12 (11%) of 110 manual faucets exceeded the HPC threshold (P<.14). A comparison of two brands of electronic faucets with manual faucets and with each other revealed that the HPC threshold was exceeded by 11 (32%) of 34 brand A faucets as compared to 12 (11%) of 110 manual faucets (P<.006). The HPC threshold was exceeded by 2 (8%) of 25 brand B faucets compared to 12 (11%) of 110 manual faucets (P<.94). Contamination rates of brand A and brand B faucets differed significantly (P<.003). Similar testing 2 months after hyperchlorination of the water supply indicated that the HPC threshold was exceeded by 16 (52%) of 31 brand A faucets compared to 10 (9.%) of 110 manual faucets (P<.0000003) and by 2 (18%) of 25 brand B faucets compared to 10 (9%) of 110 manual faucets (P=1.0). CONCLUSIONS: A certain brand of electronic water faucet used in the hospital was associated with unacceptable levels of microbial growth in water and was a continuing source of bacteria potentially hazardous to patients.

Chlorine↗

Legionella pneumophila grows adherent to surfaces in vitro and in situ.

Legionella pneumophila continues to play a role in both community- and nosocomially-acquired pneumonia. We investigated the ability of L pneumophila to adhere to various types of materials such as those found in the hospital air-cooling and portable water distribution systems. Through the use of a unique sampling apparatus, we were able to regularly acquire planktonic and sessile samples and determine the numbers of bacteria present in both populations, in vitro and in situ. Portions of these apparatuses could be aseptically removed for examination by scanning electron microscopy, or for the determination of the number of viable adherent L pneumophila. The number of bacteria present in each sample was determined by direct plate count, with presumptive L pneumophila colonies being positively identified by direct fluorescent antibody staining techniques. The results demonstrated that not only are legionellae capable of colonizing various metallic and nonmetallic surfaces but that they are preferentially found on surfaces. Surface-adherent bacteria may play a profound role as a reservoir of these potential pathogens in aquatic environments. Furthermore, these results suggest that any comprehensive legionella monitoring program must include not only water samples but also an examination of the adherent populations.

Air Conditioning↗

Disinfection of water distribution systems for legionella: a review of application procedures and methodologies.

Hospital-acquired legionella pneumonia is emerging as a major problem; potable water distribution systems have been shown to be the primary reservoirs for the legionella organisms. As a result, disinfection measures have been developed to eradicate the organism from the hospital water supply. Each disinfection modality differs in its design and application such that choosing an appropriate cost-effective control measure requires careful analysis and planning. We assess in comparative fashion the disinfection modalities of thermal eradication ("heat-and-flush"), instantaneous steam-heating system, chlorination, ultraviolet light irradiation, ozonation and metal ionization. The theoretical bases, the actual procedure or system, the logistics of implementation, the costs and personnel requirements and the advantages and disadvantages are presented for each modality. Criteria for selection of a method, the use of combinations of methods, parameters for installation, pitfalls in implementation and a plan for subsequent environmental surveillance are discussed in detail.

Cross Infection↗

"Clever Microbes": bacteriology and sanitary technology in Manchester and Chicago during the progressive age.

A neglected aspect of the history of germ theories is its use in the purification of sewage. In the 1890s, progressive reformers rapidly developed bacteriological methods of wastewater treatment. A comparison of the United Kingdom's Manchester and the United States' Chicago shows, however, that science and technology were mediated by political culture and institutions. In Manchester, a politics of deference and strong extralocal government gave the authority of scientific expertise a decisive role in policy formation. In Chicago, devolution of power to the ward bosses meant a quarter-century of defiance against the national authority and its effort to get the city to install a modern sanitation system.

Bacteriology↗