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NORWALK VIRUS - PowerPoint PPT Presentation

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NORWALK VIRUS. By: Channing Cox. TRANSMISSION. Humans are the only source for these viruses. These viruses do not multiply outside the human body.

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By: Channing Cox



  • Humans are the only source for these viruses.
  • These viruses do not multiply outside the human body.
  • The viruses are present in the feces of infected persons and can be transmitted to others when hands are not thoroughly washed after having a bowel movement.
  • When food that is not later cooked is handled by an infected person who did not wash hands after toileting, others who eat the food can become infected.
  • People also can be infected by drinking water contaminated by sewage containing one of these viruses or by consuming ice made from contaminated water.
  • There is some evidence that the viruses can be transmitted by aerosolized vomitus.


  • The signs and symptoms of Norwalk-like viruses are similar and usually occur between 24 hours and 48 hours after exposure.
  • They include nausea, vomiting, diarrhea, abdominal pain, muscle aches, headache, tiredness and low-grade fever.
  • Symptoms typically last 24 hours to 48 hours and subside on their own.


  • The U.S. Centers for Disease Control and Prevention estimates that more than 180,000 cases of Norwalk-like virus infections occur annually in the United States.
  • Some studies indicate that more than 60 percent of the U.S. population is exposed to one or more of these viruses by the age of 50.


  • Food handlers should practice careful hand washing after having a bowel movement, especially when handling food that will not be cooked later.
  • Water supplies should be protected from the risk of contamination by sewage.
  • Plumbing in dwellings and business establishments should be constructed with no cross-connections to prevent sewage from entering the drinking water supply.


  • Oral fluid and electrolyte replacement is generally adequate for the treatment of Norwalk Virus.
  • In cases of severe volume depletion, intravenous fluid and electrolyte resuscitation may be necessary.
  • Symptomatic relief can be achieved using antiemeticsfor nausea and vomiting and analgesics for myalgias and headache.


  • There are really no certain structural features that help enhance the ability to cause a disease.
  • Although, the ability of the virus to survive relatively high levels of chlorine and varying temperatures help enhance its ability to cause disease.
  • Because of the diversity of NLV strains, lack of complete cross-protection, and lack of long-term immunity, repeated infections can occur throughout life.


  • Norwalk virus - is highly contagious and often spreads in places like schools, cruise ships and nursing homes, especially during the winter.
  • Infected people usually recover in 2 to 3 days without serious or long-term health effects.


  • In January 2013, the US Centers for Disease Control and Prevention (CDC) reported that a new norovirus strain, GII.4 Sydney, which was first detected in Australia, had spread to the United States.
  • During the last 4 months of 2012, GII.4 Sydney accounted for 53% of 266 norovirus outbreaks in the United States, with roughly half of them having resulted from direct person-to-person transmission and another 20% having been foodborne.
  • The virus affects around 267 million people and causes over 200,000 deaths each year; these deaths are usually in less developed countries and in the very young, elderly and immuno-suppressed.