Viral GI II Flashcards
Poliovirus (Virology)
- Picornaviride Family
- RNA genome
- Virions stable at acidic pH
Poliovirus (Clinical)
- Three serotypes (P1, P2, P3)
- Transmission: Fecal oral route
- Incubation period between 6-20 days
- 95% of infections are ASYPMTOMATIC
- Shed in stool for WEEKS following infection
Poliovirus (Epidemiology)
Peak incidence in US (1952)
Last endemic case in US (1979)
Western Hemisphere declared free of poliovirus in 1994 (still circulates worldwide, however)
Poliovirus (Clinical Manifestations)
- Asymptomatic (95% of infections)
1) Abortive Poliomyelitis (Respiratory and GI symptoms; NO PARALYSIS –> Sore throat, Fever, Vomiting and Abd Pain, Constipation)
2) Nonparalytic Aseptic Meningitis (1-2% of infections, Nonspecific prodromal symptoms, Stiffness in back neck or legs, Last 2-10 days)
3) Flaccid Paralysis (<1% of infections; tends to show up ASYMMETRICALLY; diagnosed after one year of infection)
Poliovirus (Diagnosis)
- Virus can be isolated from STOOL
- Any isolates must be sequenced to determine if originated from wild type or vaccine strain
Poliovirus (Inactivated Vaccine)
Used in U.S. from 1955-1963
Poliovirus (Trivalent, Live attenuated oral polio vaccine (OPV))
Sabin strain
Used from 1963-2000
-Replicates in GI tract
-Shed in stool of vaccinated individuals for up to 6 weeks following inoculation
-1 of every 2 million doses the vaccine REVERTED to a more NEUROTROPIC STRAIN that caused CNS symptoms known as VACCINE-ASSOCIATED PARALYTIC POLIOMYELITIS (VAPP)
Dropped onto a SUGAR CUBE then person would ingest
Poliovirus (Treatment and Prevention)
In 2000:
-Recommendation to exclusively use INACTIVATED polio vaccine in US
-Inactivated Polio Vaccine:
Licensed in 1987
Contains antigens to ALL THREE SEROTYPES
Grown in tissue culture and inactivated by FORMALDEHYDE
NO RISK FOR VAPP
Viral Gastroenteritis (Characteristics)
Inflammation of the stomach and intestines Nausea, Diarrhea, Vomiting Viral Causes Fecal oral transmission ***Non-enveloped (can survive the gut)*** Types: -Rotaviruses -Noroviruses -Adenoviruses -Astroviruses
Gastroenteritis: Viral vs. Bacterial (Setting, Incubation Period, Vomiting, Diarrhea, Diagnosis)
Setting: Similar in developing/developed countries VS. More common in settings with poor hygiene/sanitation
Incubation: 1-3 days; shorter for norovirus (viruses need to get into cells and replicate before causing damage) VS. a few hours to 7 days (Pre-formed toxin)
Vomiting: Prominent VS. Common w/ bacteria producing preformed toxins
Diarrhea: Common, WATERY VS. Prominent and frequently BLOODY
Diagnosis: Exclusion and immunoassays for rotavirus and adenovirus VS. Culture of stool specimens
Signs of Severe Dehydration
- Rapid, weak pulse
- Sunken eyes
- Tears ABSENT
- Skin TENTING
- Lack of urination
Rotavirus (Disease Burden in the US)
- 95% of children infected by age 5
- Most severe disease in children 3-24 months
- Highest incidence among children 3-35 months
- Responsible for 5-10% of all gastroenteritis episode in children <5 years old
Rotavirus (Clinical Presentation)
- dsRNA genome that is segmented*
- Incubation period 1-3 days
- Vomiting and diarrhea duration 4-7 days, occasional cough, and coryza (inflammation of mucous membranes)
- 1/3 of patients = fever >102 F
- Increased risk in young, malnourished, immunodeficiences, bone marrow/liver transplants
NOT A MAJOR OPPORTUNISTIC PATHOGEN IN HIV INFECTIONS*
Most Prevalent Strains of Rotavirus
G1 (75%) > G2 (11%) > G9 (3.2%)
Rotavirus (Pathology)
1) Infect intestinal epithelium and cause damage
2) Infect tips of VILLI, which become BLUNTED and DAMAGED
3) Causes MALABSORPTIVE DIARRHEA
- **Need < 10 virus particle to initiate infection
- ** >10 billion particles released/g stool
Rotavirus also produces a toxin (NSP4) that causes release of Calcium (Ca2+)
Rotavirus (Diagnosis)
- EIA from stool sample (EIA = Enzyme Immunoassay; uses antibodies to find Rotavirus)
- Less commonly: EM, RT-PCR
Rotavirus (Treatment)
Oral Rehydration
IV Rehydration with severe disease
Rotavirus (Prevention)
- Prevent fecal-oral transmission (sanitize fomites, e.g. toys; Handwashing)
- IgA in colostrums (First breast milk produced in a nursing mother)
- Vaccines
Rotavirus (Vaccine)
Two live attenuated, ORAL vaccines
1) 2006 - Rotateq
- Protective G1-G4, G9
- Product of REASSORTMENT between HUMAN and BOVINE rotaviruses
2) 2008 - Rotatrix
- Live attenuated strain of Human rotavirus GIPIA[8]
ACIP –> unviersal vaccination of infants before 12 weeks
No increased risk of intussusceptions (slippage of intestial lining causing blockage; occured with the original vaccines)
Noroviruses (Characteristics)
Causes 96% of nonbacterial gastroenteritis in the US
Incubation period of 24-48 hours
Nausea, vomiting, diarrhea for 24-60 hours
Low grade fever in about half of patients
Afflicts ALL AGE GROUPS
Pathology similar to Rotavirus
Noroviruses (Virology)
-Caliciviridae Family
-Non-enveloped
+ssRNA
-NORWALK VIRUS is founding member
-Virus shows Preference for individuals expressing specific HISTO-BLOOD GROUP ANTIGENS
(Type B are more likely to be infected by Norwalk virus)
Noroviruses (Clinical Info)
As little as 100 virions can cause infection
Transmission: Fecal oral route
- Person to person (Close personal contact; droplets from VOMITUS)
- Fomites
- Waterborne (3%)
- Contaminated food (39%) (Food handler; Contamination prior to preparation)
- Raspberries and Oysters (or other filter feeders)*
Adenoviruses (Characteristics)
***dsDNA genome*** Naked capsid Fiber protein at vertices (toxic cells) Serotypes 40 and 41 cause gastroenteritis (IMPORTANT to distinguish these types from 2,4,7 which cause URI symptoms) -Shed from GI tract -Primarily in CHILDREN -Incubation period 8-10 days -Watery, NON-BLOODY diarrhea 7-8 days -May be accompanied by vomiting and fever -NO SEASONAL VARIATION
Adenovirus (Diagnosis)
Antibody-based
