Water-borne diseases

This may also have been a factor in the conquering of the known world by the Roman Legions. Expeditionary and seige forces, even today but much more so then, are at risk for water-borne diseases. The practice of the Roman army to carry with it substantial wine suppHes is seen as sound militarily for health reasons, rather than just from the standpoint of the enjoyment of the soldiers. Recent study indicates that tourist-type diarrheas are less frequently encountered if wine is consumed rather than water, even bottled water (20). 

However, the laws and regulatory programmes regarding water quality cope with most of the problems and legislation generally protects the population in developed countries, even when scarcity forces the use of non-conventional water resources. Outbreaks of water-borne diseases in these countries are more linked to intense rainfall events, mostly to those that follow drought periods, rather than to drought itself [1 ]. 

The water-related or water-associated infectious diseases are typically arranged in four classes from the environmental engineering point of view, although more complex categorizations have also been proposed [14]. These categories are faecal-oral water-borne diseases, water-washed diseases, water-based diseases and diseases transmitted by water-associated insect vectors. Each type has different causes and potential solutions. Too often the term water-borne disease is erroneously used to name all of them without distinction. 

The faecal-oral water-borne diseases, though with very different intensity, affect both developed and developing countries. These are the most important by number of affected people worldwide (Table 1). The other three categories affect basically developing countries. The water-washed affects those with water scarcity, whereas... 

The most important pathogens causing faecal-oral water-borne diseases, with the exception of helmints (Ascaris, Trichurus, Taenia, etc.) are compiled in Table 2. These, virtually absent in the developed countries, are stiU highly prevalent in developing countries, though without causing serious illness [8]. 

Sinclair, R. G., Jones, E. L., and Gerba, C. P. (2009). Viruses in recreational water-borne disease outbreaks A review. /. Appl. Microbiol. 107,1769-1780. 

The biological contamination and the hardness of underground water are the two very serious problems of water. Dissolved salts deteriorate water quality and may cause diseases related to joints and bones, while infected water may cause many water-borne diseases such as cholera, dysentery, typhoid etc. Ultrasound may disinfect the potable water by blasting off micro organisms such as zooplanktons, phytoplanktons, pathogenic bacteria and produce germ-free water in few minutes of... 

By sterilisation is understood the destruction of all organisms4 in the water, whether pathogenic or not. In the absence of suitable mechanical filters or in cases of doubt as to the efficiency of the filters in removing pathogenic germs, sterilisation should be resorted to, for this is the only sure method of preventing the spread of water-borne diseases. 

Nevertheless, in many parts of the world—and largely because of poor sanitation regarding water and sewage—a significant portion of the world s population is chronically infected. More than 250 million new cases of water-borne disease are reported each year, about 10 million of which result in death (about 50% of these are children under five). 

In Paris, when water is chlorinated as at the Ivry plant, it is always dechlorinated with sodium hyposulfite before being pumped to the consumer. The water-borne disease rate since 1930 has under these circumstances been less than 1.6 infections per 100,000 inhabitants, and today the trend is to less than 1 per 100,000. 

Fig. 1. USA population and incidence of major water-borne diseases.

Technical solutions have been developed to a number of important environmental problems. One of the most important contributions to human health has been the chemical purification of drinking water, which has nearly eliminated water-borne diseases in developed countries.2 Disinfection with chlorine and ozonation have been used to eliminate pathogens, and advances in membrane science have enabled removal of various substances from water. Many of the technical solutions have been developed in response to unexpected problems created by other technical advances. 

Before leaving this sub-section on chlorine as a disinfectant, we should note that the majority of the Asian cities still do use chlorine to disinfect drinking water. The benefits in term of protection from water-borne diseases in Asia far overweigh the possible hazard from, for example, 10 or 20 ppb of trihalomethanes. Disinfection with chlorine may possibly pose a cancer risk in old age no disinfection in the Asian region does mean a substantial chance of dying from typhoid fever or cholera as a child or young adult. However, as we have seen in Table 1, there are different methods of disinfection and we consider some of these alternatives to chlorination. 

The quality of water is important to human health. Water-borne diseases cause about 80% of the world s sickness. Because humans drink about 2 L of water per day, even small amounts of toxic compounds in drinking water have significant effects over time. But, what is pure water What is polluted water With numerous terms such as pure, purified, distilled, and disinfected to describe our drinking water, how do we know what we are getting ... 

The conditions of refugee and IDP camps—while facilitating access of health programmes to displaced populations— present health challenges of their own, with crowded conditions creating additional risks for rapid transmission of disease. Significant risk for transmission of water-borne diseases such as cholera and hepatitis E has been documented in camp settings. 

Incubation periods for water-borne diseases vary considerably between causative organisms. Qiolera has an incubation period of aroimd 5 days, while cr3q>tosporidiosis has an incubation period of approximately 14 days. 

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