Waterborne Rotavirus: A Risk Assessment

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Waterborne Rotavirus A Risk Assessment

• Gerba, C., Rose, J.B., Haas, C.N., Crabtree,
  K.D., (1996) Waterborne Rotavirus A Risk
  Assessment. Water Research. 30(12), 2929-2940.
• Charmaine Lynch

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Topic

• This paper presents a risk assessment approach
• Used to estimate the public health impacts from
  exposure to human rotavirus
• Drinking and recreational waters

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Introduction

• Assessing human health risks from enteric
  pathogens in water has largely been done on an
  empirical basis in the past
• Microbial risk assessment is still a new area
• United States Environmental Protection Agency
  (USEPA)
• Has recommended that drinking water treatment be
  provided to ensure that populations are not
  subject to risk of infection greater than 110,000

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Rotavirus

• Discovered in 1973
• Classified with the reoviruses and orbiviruses
• family Reoviridae
• Resistant to inactivation at low(3.5) and high
  pH(10.0)
• Segmented double-strained RNA viruses

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Rotavirus

• Six distinct groups from A-F
• Groups A, B, C are found in humans and animals
• Groups D, E, F found only in animals

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Materials and Methods

• Published literature was reviewed
• Characterize nature of disease
• Documented waterborne outbreaks
• Attack rates
• Percent of infected population
• Hospitalization and mortality

• Risk characterization
• Used established dose-response models

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ResultsNature of the organism and disease
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Nature of the organism and disease

• Waterborne outbreaks are characterized by high
  attack rates in adults
• Possible explanation
• adults consume more tapwater than children

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Incidence of the disease

• 90 of all children are infected by rotaviruses
  by the end of the third year of life
• Estimated over one million cases of severe
  diarrhea in 1-4 age group
• caused by rotaviruses annually
• 150 deaths
• Third World countries
• 125 million

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Symptoms/Hospitalization

• Vomiting
• Abdominal distress
• Diarrhea
• Mild dehydration
• 60 of rotaviral infections in adults were
  asymtomatic
• 28 for children

• 50 of hospitalized cases
• acute diarrhea
• children under 2

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Immunity

• All adults have evidence of previous infection
  with rotavirus
• Serum antibodies to rotavirus occurs between the
  ages of 6 and 24 months
• High attack rates in the elderly
• decrease in protective immunity with age

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Occurrence in water and potential for exposure

• Wastewater
• information limited
• occurs in winter months
• concentration in rotavirus in raw sewage (90,700)
• Unchlorinated range from 750 to 1687 per liter
• chlorinated 906 per liter

• Surface water
• average concentrations ranging from 0.66 to 29
  per liter
• highest in untreated sewage discharges

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Drinking water and groundwater

• Rotavirus found more commonly in drinking water
  after treatment during the rainy season when
  treatment plant was having difficulty operating
  properly

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Discussion/Conclusion

• Impact on society
• direct medical costs
• loss of work
• quality of life and mortality
• Severe for the very young and elderly
• immunocompromised

• Protective immunity
• short duration
• reinfection occurs throughout life
• Vaccines have not been successful
• Proven route of transmission is by fecal-oral
  route
• environmental contact
• ingestion of contaminated water or food

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Discussion/Conclusion

• Swimming in contaminated waters results in a
  greater risk of gastroenteritis
• Why more waterborne outbreaks have not been
  documented?
• Infrequent occurrence in developed countries
• investigation not conducted

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Conclusion

• From the assessment
• major limitation in assessing risks
• lack of quantitative data
• Limitations
• current methods for detection in water
• Rotavirus should receive further study for
  waterborne disease can be better quantified