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Overview
Viruses are a major cause of waterborne and water related diseases, waterborne diseases is an illness that is caused by water that is contaminated by human and animal urine and feces that contain pathogenic microorganisms. A subject can get infected through contact or consumption of the contaminated water. Viruses affect all living organism from single cellular plants, bacteria and animal to highest forms of plants and animals including human beings. Virus interacting with their host can be done via several methods and mechanisms, some viruses can be host specific like HIV and some can be less host specific such as Influenza viruses. Different viruses can have different routes of transmission like HIV is directly transferred by contaminated body fluids from an infected host into the tissue or bloodstream of a new host and Influenza is airborne transmitted through inhalation of contaminated air containing viral particles by a new host. Also the large group of enteric viruses that primarily infect the intestinal tract by the fecal oral route which usually includes the ingestion of food water contaminated with viruses. However that’s not always the case, since some viruses can transmit thought all three modes.

Water virology started around half a century ago, with scientists attempting to detect poliovirus in water samples. Since then, other enteric viruses that are responsible for gastroenteritis and hepatitis, among many more varieties of virus strains, have replaced enteroviruses as the main aim for detection in the water environment. Viruses play an important role in biological mechanisms; also nature preserves equilibrium among living organisms. Today has come a time, which man has disturbed the equilibrium of living organisms on earth and how nature keeps heading for a lost battle by innovating new forms of viruses like human immunodeficiency virus, commonly known as HIV, and mutants of old stalwarts such as influenza viruses with new battle strategies.

Major Outbreaks
Virology was born after a large hepatitis outbreak was confirmed in New Delhi between December 1955 and January 1956.

Viruses which reduced the number of people as demonstrated by variola viruses which killed an estimated 10 to 15 million human beings per year until 1967. Smallpox was finally elimnated in 1977 by extinction of the virus, and the impact of viruses such as influenza, poliomyelitis and measles was controlled by vaccination.

It is estimated that in the 1980s a child died approximately every six seconds from diarrhea confirmed by WHO.It would appear that the most likely cause of the hepatitis referred to was hepatitis A and/or E, both which are enteric viruses , typically transmitted by food and water.Extreme examples include the outbreak of 300,000 cases of hepatitis A and 25,000 cases of gastroenteritis in 1988 in Shangai caused by shellfish harvsted from sewage polluted estuary. In 1991, an outbreak of 79,000 cases of hepatitis E in Kanpur was ascribed to polluting drinking water.

Most recent outbreak of hepatitis E was in South Sudan which killed 88 people, more than 112,000 Sudanese refugees were affected by the hepatitis outbreak Hep Medical charity Medecins Sans Frontieres (MSF) said it had treated almost 4,000 patients since the outbreak was identified in South Sudan in July 2012. Hepatitis E caused liver infections and was spread by drinking water contaminated with faeces.

Viruses present in water
Sewage contaminated water contains many viruses, over hundred species are reported and lead to diseases that affect human beings. For example hepatitis, gastroenteritis, meningitis, fever, rash, conjunctivitis. Even today many more are being discovered, although only some of these viruses lead to viral pathogens that demonstrate to be waterborne transmitted.

Table 1

Virus survival in water
Viruses need a suitable environment to survive in, there are many characteristics that control the survival of viruses in water such as temperature, light, pH, salts, organic matter, suspended solids or sediments, and air–water interfaces.

Temperature
Temperature has the highest effect on virus’s survival in water since lower temperatures are the key to longer periods of viruses. The rate of protein, nucleic acid denatures and chemical reactions that destroy the viral capsid are affected by temperature due to viruses will able to survive best in freezing temperatures. Hepatitis A, adenoviruses and parvoviruses have the highest ability of survival in low temperatures amongst enteric viruses.

Light
Ultraviolet light (UV) is the light in sunlight and can inactivate by causing cross-linking among the nucleotides. Many viruses in water are exterminated in the presence of sunlight compared to the viruses dying at night. Therefore, viruses denatured more in summer than winter.Double stranded DNA viruses like adenoviruses are more resistant to UV light inactivation than enteroviruses because they can use their host cell to repair the damage caused by the UV light.

Visible light can also affect virus survival by a process called photodynamic inactivation but the length and intensity of a light that is exposed to virus can change the inactivation rate.

pH
The pH of most natural water is pH 5-9, which enteric viruses are stable in these conditions on the other hand many enteric viruses are more stable at pH 3-5 than at pH 9 and 12. Enteroviruses can survive at pH 11-11.5 and 1-2 but for only short periods. Adenoviruses and rotaviruses are delicate to a pH of 10 or greater and leads to inactivation.

Salts
Viruses survive longer in freshwater than seawater because of the microorganisms present rather than the high concentration of salt.

Virus removal in water
Water that is intended for drinking should go through the process of virus removal since it is vital because of the increase in human population will lead to the increase of waste levels. Human pathogenic virus can be found in water and the risk to human health is critical. Precautions that should be taken are when disinfecting the water only, maybe insufficient, more treatments are needed and failure to find a virus does not mean that viruses do not exist in the water but further testings are required.

Epidemiology suggest that the most common virus found is hepatitis A/E and gastroenteritis, caliciviruses, astroviruses and enteric viruses, laboratories are still looking for a improved services that detect these difficult viruses.

Treatment
Reducing the amount of viruses in drinking water can be accomplished by various treatments. In virus removal, it is important to consider the virus size, since the size is very small. Water treatments like concentration, sedimentation and filtration are significant for virus removal, but because of the small size, some viruses escape these removal processes. Whereas to detect a virus in sewage is considered easier that to detect a virus in drinking water is considered a difficult method.

Filtering
Filtering large volume seems an issue for whether co-concentrated substances might interfere with virus isolation and/or detection. Using a molecular virus detector does not succeed in guaranteeing a viruses infectivity. Virus assay in cell cultures requires a secondary concentration step, but not all human waterborne viruses can be detected in cell cultures.

Concentration
Concentration is an important step because the viruses population maybe a small number, performing this process correctly is highly sufficient because it is fast, simple, inexpensive and gives accurate results.

Prevention of water viruses
The quality of drinking water is ensured through the framework of water safety plans. The illnesses that are caused by feces only ten percent of that is treated the rest is emptied into river,lakes and oceans. By improving the water supply, sanitation, hygiene and management of our water resources could prevent ten percent of the global diseases.

Other Concerns
Half of the hospital beds occupied in the world are related to the lack of safe drinking water, which also leads to the 88% of global cases of diarrhea  and the 90% of  deaths of diarreaheal diseases under five year olds, which mostly occurs in developing countries due to poverty and high cost of safe water.

Approximately 1.1 billion do not have access to improved water and 2.4 billion do not have access to sanitation facilities. Which lead to 2 million death each year, this could be prevented but due to the lack of commitment 50% of these projects fail. Also another problem includes the lack of priority and financial resources.