Agents of Viral Gastroenteritis

1
Agents of Viral Gastroenteritis

• Erik Reisdorf CLS M (NCA)
• Advanced Microbiologist
• Communicable Disease Division
• Wisconsin State Laboratory of Hygiene
• February 25, 2004

2
ACUTE INFECTIOUS GASTROENTERITISPUBLIC HEALTH
IMPACT

• United States
• Second most common clinical entity
• Greatest clinical impact on children lt 5
• 500,000 physician visits
• 55,000 children hospitalized per year
• gt500 deaths per year
• 1 billion in total costs
• Worldwide
• Estimated 3-5 billion cases occur annually
• 5-10 million deaths annually primarily in
  developing countries

3
Incidence of Foodborne Illness
4
Etiologic Agents Associated With FBOs 1991-2000
(n231)
5
FOODBORNE WATERBORNE GASTROENTERITIS

• An Emerging Public Health Problem

6
FOODBORNE WATERBORNE GASTROENTERITIS

• The Viral Agents
• Norovirus (norwalk-like)
• Rotavirus
• Adenovirus 40/41
• Astrovirus
• Other?

7
FOODBORNE WATERBORNE GASTROENTERITIS

• CLUES AS TO ETIOLOGY
• Clinical Features
• Incubation Period
• Duration of Illness
• Seasonality
• Geographic Location

8
FOODBORNE WATERBORNE GASTROENTERITIS

• Clinical Clues

9
FOODBORNE WATERBORNE GASTROENTERITIS CLINICAL
CLUES (V)

• Nausea, Vomiting, and Diarrhea
• Incubation 24 - 48 hours
• Duration 24 - 48 hours
• Etiology norovirus (previously known as
  norwalk-like virus)

10
FOODBORNE WATERBORNE GASTROENTERITIS NOROVIRUS
11
FOODBORNE WATERBORNE GASTROENTERITIS

• Helpful Hints for the Clueless Clinician
• Bloody (with mucus) diarrhea
• Fever
• Chronicity
• Age
• Seasonality
• Two or more people involved
• Retrospective chart review
• When in doubt, contact your LPHA

12
VIRAL GASTROENTERITIS

• Major Etiologic Agents
• Norovirus
• Largest cause of outbreaks of nonbacterial
  gastroenteritis (gt90)
• Rotaviruses
• Adenovirus Types 40 and 41
• Astroviruses

13
OTHER VIRUSES IMPLICATED IN GASTROENTERITIS

• SRSVs
• coronavirus
• Pestivirus
• Picobirnavirus
• Torovirus
• Parvovirus
• Etiological role and public health significance
  unclear!

14
VIRAL GASTROENTERITIS

• Enteroviruses Another Major Player?
• NOT!

15
VIRAL GASTROENTERITIS

• Rotaviruses
• Family Reoviridae
• dsRNA (11 segments), non-enveloped 70nm
• 5 groups, A - E
• Group A (subtypes 1 - 4) - 1? human pathogens
• Group B - extensive outbreaks in China
• Group C - occasional illness worldwide
• Groups D and E - animal pathogens

16
VIRAL GASTROENTERITIS

• Rotavirus Clinical Illness
• Incubation period 1 - 3 days
• Duration 3 - 8 days
• Characteristic clinical triad
• fever
• vomiting
• diarrhea
• Frequent coryza and cough
• Dehydration is leading complication

17
VIRAL GASTROENTERITIS

• Rotavirus Epidemiology
• Max. incidence of illness 6 - 24 months
• Reinfection common throughout life
• Infections at lt 6 months and gt 5 years of age
  often asymptomatic or mild
• Seasonality Marked winter-spring peak in WI
• Transmission person-to-person fecal - oral
  respiratory?

18
ROTAVIRUS IN WISCONSIN
19
VIRAL GASTROENTERITIS

• Caliciviruses
• Family Caliciviridae
• genus norovirus
• ssRNA, non-enveloped 26 - 34 nm
• 4 genogroups GI 25 GII 75 GIIIIV animals
• Many different genetic clusters (gt17)

20
VIRAL GASTROENTERITIS

• Norovirus Clinical Illness
• Incubation 1-2 days
• Duration 2-3 days
• Abrupt onset of nausea and vomiting with
  prostration and malaise
• Nausea, vomiting, diarrhea, and headache gt50

21
VIRAL GASTROENTERITIS

• Norovirus Epidemiology
• 23 million annually
• All ages affected
• Occurs year around
• Winter vomiting disease
• Explosive family, institutional, and
  community-wide outbreaks
• asymptomatic excretion

22
VIRAL GASTROENTERITIS

• Norovirus Characteristics
• Non cultivitable
• Vomitus infectious
• Reservoir
• Highly transmissible
• Environmentally stable

23
Seasonality
24
Person-to-Person Spread
25
Wisconsin winter of 2002-2003
26
Wisconsin

• November 2002 through February 2003 there was a
  marked increase outbreaks
• 9 institutional
• 2000 2
• 2001 4

27
The National Picture

• Trend reflected nationally
• Washington State
• November- December 2002 10 outbreaks (6 LTCF)
• New Hampshire
• November-December 2002 29 outbreaks (LTCF)
• NYC
• November-January 2003 66 outbreaks of AGE (51
  LTCF)

28
Theories???
29
VIRAL GASTROENTERITIS

• Adenoviruses
• Family Adenoviridae
• dsDNA, non-enveloped 70 - 75 nm
• 2 enteric serotypes 40 and 41

30
VIRAL GASTROENTERITIS

• Adenovirus 40/41 Clinical Illness
• Incubation 7 - 8 days
• Duration 8 - 12 days
• Diarrhea predominates

31
VIRAL GASTROENTERITIS

• Adenovirus 40/41 Epidemiology
• Second leading cause of cases (5-20) and
  hospitalizations in infants
• Occurs year around no seasonal peak
• Predominates in late fall and winter
• Asymptomatic or mild illness in older children,
  adults
• Transmission person-to-person

32
VIRAL GASTROENTERITIS

• Astroviruses
• Family Astroviridae
• ssRNA, non-enveloped 28 - 30 nm
• gt 5 serotypes?

33
VIRAL GASTROENTERITIS

• Astrovirus Clinical Illness
• Incubation 3 - 4 days
• Duration lt 5 days
• Illness milder than Rotavirus
• Diarrhea and low grade fever predominate

34
VIRAL GASTROENTERITIS

• Astrovirus Epidemiology
• Community impact uncertain
• Most common in lt 3 years of age often
  asymptomatic
• Mild illness in adults
• Winter peak in temperate climates
• Transmission person-to-person water/food?

35
GASTROENTERITIS VIRUSES

• PATHOGENETIC CHARACTERISTICS
• Type of infection acute, localized
• Gastrointestinal tract is target organ
• Incubation period generally short, 1-4days
• Exception is adenovirus type 40 and 41infections
  (7-8days)
• Mechanism of transmission person-to-person via
  fecal-oral route food-and water-borne
• Viruses environmentally stable
• Frequency of inapparent infections low (except
  Astrovirus) for primary infection increase with
  re-infection (Rotavirus)
• Symptomatic re-infections common
• Implies poor long-term immunity
• Prolonged virus shedding common with adenovirus
  can occur with rotavirus
• Illnesses often more severe in compromised hosts

36
VIRAL GASTROENTERITIS

• Laboratory Diagnosis

37
VIRAL GASTROENTERITIS

• Guidelines for Specimen Collection
• Collect stool within 48 hours after onset
• Bulk sample no preservatives rectal swabs of
  little value
• Refrigerate at 4C do not freeze

38
VIRAL GASTROENTERITIS

• Laboratory Testing Available
• Rotavirus EIA, LA, EM, RT-PCR
• Adenovirus 40/41 EIA
• Norovirus RT-PCR, EM
• Astrovirus RT-PCR, EM
• Method of Choice

39
VIRAL GASTROENTERITIS

• Treatment
• Fluid and electrolyte replacement

40
VIRAL GASTROENTERITIS

• Prevention
• Hand washing hygiene cohorting infants
• Rotavirus vaccine
• Live, attenuated, reassortant, oral vaccine
• Directed against group A, serotypes 1 - 4
• Universal administration 2, 4 and 6 months
• USE OF THE VACCINE HAS BEEN SUSPENDED DUE TO
  CLINICAL COMPLICATIONS!