Viruses

• Members of the enteric viruses infect the gastrointestinal tract of humans and animals, and are excreted in feces. If the feces enter a surface water system, there is potential for the spread of waterborne disease. Enteric viruses of particular concern in water are hepatitis A, Norwalk-type viruses, rotaviruses, adenoviruses, enteroviruses, and reoviruses.
  1. Hepatitis A virus (HAV): HAV is readily transmitted through water. HAV causes infectious hepatitis, an illness characterized by inflammation and necrosis of the liver. HAV can be removed from drinking water through coagulation, flocculation, and filtration (AWWA, 1990).
     
     
     http://www.cdc.gov/ncidod/diseases/hepatitis/slideset/hep_e/images/slide_1.jpg
  2. Norwalk-type viruses: Norwalk-type viruses cause acute epidemic gastroenteritis. No information is available on their occurrence in water (AWWA, 1990).
     
     
     http://www.ela-iet.com/el00005.htm
  3. Rotaviruses: Rotaviruses cause acute gastroenteritis, especially in children. Like HAV, rotaviruses can be removed from drinking water through coagulation, flocculation, and filtration (AWWA, 1990).
     
     
     http://www.qub.ac.uk/afs/vs/vsd6.gif
  4. Adenoviruses: Adenoviruses can infect both the intestine and the upper respiratory tract. Adenoviruses have been detected in wastewater and contaminated surface water, but not in drinking water (AWWA, 1990).
     
     
     http://www.tulane.edu/~dmsander/WWW/335/Adeno1.gif
  5. Enteroviruses: Enteroviruses can infect both the intestine and the upper respiratory tract. Enteroviruses have been detected in wastewater, natural water, and finished drinking water. No incidents of waterborne disease have been documented, so the importance of this virus as a disease- causing agent is uncertain (AWWA, 1990).
     
     
     http://web.uct.ac.za/depts/mmi/stannard/entero.gif
  6. Reoviruses: Reoviruses can infect both the intestine and the upper respiratory tract. Reoviruses have been detected in wastewater, natural water, and finished drinking water. No incidents of waterborne disease have been documented, so the importance of this virus as a disease-causing agent is uncertain (AWWA, 1990).
     
     
     http://www.kcom.edu/faculty/chamberlain/Website/Lects/VIRAL.HTM

Certain environmental factors may affect the viability of viruses. Viability is maintained when high levels of suspended sediment in water provides substrates to which the viruses can adsorb. Sorbed viruses may remain nearly 100% viable. Viability decreases when high water temperatures and high sunlight intensity dessicate and inactivate viruses (Kubek et al., 1990).

Numerical Categories:

Designated Use

Human Consumption: The maximum contaminant level goal (not enforced) for viruses is zero viruses per 100 ml sample of drinking water. The maximum contaminant level (MCL) is simply whatever level the best available technology can achieve (Kubek et al., 1990).

Health Effects: Members of the enteric viruses infect the gastrointestinal tract of humans and may be spread through water. Enteric viruses of particular concern in water are hepatitis A, Norwalk-type viruses, rotaviruses, adenoviruses, enteroviruses, and reoviruses. Hepatitus A virus causes hepatitus. Rotaviruses are the primary cause of childhood gastroenteritis and adult's "traveler's diarrhea." Adenoviruses may cause eye infections and respiratory disease. Entero viruses may cause paralysis, meningitis, respiratory illness, and diarrhea. (Kubek et al., 1990; AWWA, 1990).

Environmental Effects: Members of the enteric viruses infect the gastrointestinal tract of mammals (Kubek et al., 1990).

Sources:

1. Nonpoint:
   • Agriculture: Viruses may be found in livestock excrement from barnyards, pastures, rangelands, feedlots, and uncontrolled manure storage areas; and areas of land application of manure and sewage sludge.
   • Residential and Urban: Failed on-site wastewater disposal systems can contribute viruses to a water body. Urban runoff may convey viruses from litter and domestic pet excreta.
   • Other: Viruses in ground water may originate from landfill oxidation ponds and deep well injection of sewage. Other surface water sources include boats that discharge raw sewage overboard; excreta from wild animals in surrounding watersheds; and excreta from wildfowl that congregate on the water body.
2. Point source: Sewered communities may not have enough capacity to treat the extremely large volume of water resulting from large rainfalls. Periodically, treatment facilities may need to bypass treatment of their wastewater. In this case, water containing viruses is discharged directly into the surface water body. Estuaries may be particularly susceptible to viral contamination from offshore sewage sludge dumping and offshore sewage pipe outfalls (Kennish, 1992).

Mode of Transport: Transport in water: Virus-laden wastewater can either leach into groundwater and eventually seep into a surface water body, or rise to the ground surface and move to a water body in overland flow. Viruses in overland flow can be transported freely and within organic particles.

• Waterborne diseases may be transmitted to humans through:
• Drinking water: municipal, domestic, industrial, and individual supplies.
• Primary contact recreation: bathing, water skiing.
• Secondary contact: boating, fishing.
• Ingestion of shellfish.

Additional Information:

1. The Big Picture Book of Viruses
2. Introduction to the Viruses
3. Visualization of Viruses
4. How Viruses Work

(APHA, 1992) Three-step process:

NCSU Water Quality Group

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