Pathogenic Bacteria and Viruses in Water

Drinking water is very vulnerable to contamination by pathogenic bacteria and viruses – micro-organisms that are capable of causing disease. This is because pathogenic bacteria and viruses are tiny micro-organisms that cannot be detected with the naked eye. Yet, they are everywhere, and can easily wash into surface waters with runoff, or leach through soil to contaminate groundwater sources without us knowing.

Bacteria are tiny single celled organisms, typically measuring between 0.4 -14 micro-meters long, and between 0.2 – 12 micro-meters wide, that are able to rapidly multiply by DNA replication and cell division when conditions are favorable. They thrive in a variety of habitats and conditions – and many species can exist in water where they can spread disease. Examples of waterborne bacteria that can cause disease include E.coli, Vibrio cholera, Salmonella spp, Campylobacter spp, Shigella spp, and Staphylococcus aureus.

Viruses are even smaller than bacteria, measuring between 0.02 – 0.09 micro-meters, which allows them to easily pass through all but the finest pore size filters. Viruses live in a dormant state in the environment, but once they invade a host, they come to life and quickly take control of the host cell's metabolism, replicating their DNA to the host cell, causing infection. As viruses do not naturally occur in the body, the body's natural defense mechanism steps in to try and rid it of this foreign invader. It does this by secreting mucous, which is generally how the virus is spread further. Once the virus exits the body, it again lies dormant until it finds another host to invade. While over a hundred animal and human enteric viruses that can be transmitted by water are known to exist, the more common diseases caused by waterborne viruses include hepatitis A, enterovirus, rotavirus, and norovirus.

Other pathogenic organisms that can be transmitted in water include protozoa – miniscule organisms that are very difficult to eradicate due to their ingenious mechanisms of self defense using highly impenetrable protective shields to coat the cysts (eggs) as they leave the host to lie dormant in water. This often makes water treatment ineffective at eradicating these pathogens, which are also capable of slipping through all but the finest of fine filter pore sizes. Two common disease causing protozoans include Cryptosporidium parvum and Giardia lambli – two of the most widespread pathogens responsible for water related health issues.

Some pathogenic micro-organisms, such as Legionella bacteria, which is responsible for causing Legionnaire's disease, occur naturally in water, however most pathogenic bacteria and viruses in water originate from human or animal feces that enters the water source either by runoff, or by seeping through pores in the soil to pollute groundwater. The most common symptoms of infection from a water borne enteric bacterium or virus is gastro-intestinal upsets, vomiting, and fever.

Water sources situated near agricultural farmlands are vulnerable to contamination from pathogenic bacteria and viruses originating from livestock feces, while sewage discharges or leaking septic tanks can also pollute water sources. Surface water is more prone to contamination, especially by protozoan cysts, while groundwater is slightly less vulnerable, as soil particles tend to act as a natural filter to remove pollutants as they filter through the soil. However, pathogenic bacteria and viruses can still enter groundwater, where they can pose a health risk to well owners and others that use this as a source of drinking water.

Water treatment facilities commonly disinfect drinking water through chlorination to eradicate pathogenic micro-organisms. However, the protozoan cysts are more persistent than bacteria and viruses, and may still linger in drinking water to pose a health risk.

While pathogenic micro-organisms are invisible to the naked eye, and thus impossible to detect in drinking water without having the water tested, one symptom that could indicate that your water may be contaminated with pathogenic bacteria or viruses is if it has a bad odor – particularly if it smells like sewage, which could be a sign that the water has been contaminated by a leaking septic tank or sewage spill. If your water smells bad, do not drink it, and have it tested immediately. If you are unsure, invest in a top of the range drinking water filters with an ultra fine micro-pore mesh, as these are capable of filtering out pathogenic bacteria and viruses, and in most cases those elusive pathogenic protozoa too, to render your drinking water safe to drink.


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