L41: Polio and Viral Gastroenteritis

Question 1

Poliovirus characteristics

Answer 1

Picornaviridae family, RNA genome, stable at acidic pH

Question 2

Transmission of poliovirus

Answer 2

Primarily fecal-oral (shed in stool for weeks following infection)

Question 3

Incubation period of poliovirus

Answer 3

6-20 days

Question 4

Epidemiology of poliovirus

Answer 4

Peak incidence in US was 1952 but last endemic case in US was 1979 – endemic still in Afghanistan, Nigeria, and Pakistan

Question 5

Clinical manifestations of poliovirus

Answer 5

95% of cases asymptomatic, can lead to abortive poliomyelitis (sore throat, fever, vomiting/abdominal pain, constipation), nonparalytic aseptic meningitis (prodomal symptoms, stiffness in back/neck/legs, 1-2%), or flaccid paralysis (often asymmetric and in lower limbs, normally leads to permanent paralysis)

Question 6

Diagnosis of poliovirus

Answer 6

Can be isolated from stool, isolates must be sequenced to determine if originated from wild type or vaccine strain

Question 7

Vaccine for poliovirus (past and present)

Answer 7

Inactivated polio vaccine used in 50’s and 60’s, switched to live attenuated from 1963-2000 but 1/2 million got VAPP – switched back to inactivated in 2000

Question 8

Vaccine-Associated Paralytic Poliomyelitis (VAPP)

Answer 8

Neurotropic strain reversion of live attenuated vaccine that caused CNS symptoms

Question 9

Viral causes of gastroenteritis (4 types)

Answer 9

Fecal-oral transmission, non-enveloped:

• -Rotaviruses
• -Noroviruses
• -Adenoviruses
• -Astroviruses

Question 10

Differences between viral and bacterial gastroenteritis

Answer 10

Viral: longer incubation period, more vomiting, NON-bloody diarrhea, diagnosis often due to exclusion
Bacterial: more common with poor hygiene and sanitation, very short incubation period, less vomiting, prominent/frequently bloody diarrhea, identified by culture

Question 11

Dehydration with viral gastroenteritis

Answer 11

Biggest worry, important to look for in infants – signs include rapid weak pulse, sunken eyes, absent tears, skin tenting, lack of urination – treated with oral rehydration therapy (mild) or IV rehydration (severe)

Question 12

Epidemiology of rotavirus

Answer 12

95% of children infected by age 5, most severe disease 3-24 mos

Question 13

Clinical presentation of rotavirus

Answer 13

Incubation period 1-3 days, vomiting and diarrhea 4-7 days, fever >102 F in 1/3 of patients, risk for life-threatening complications of acute infections in very young or malnourished – not a major opportunistic pathogen in HIV infections

Question 14

Most common strain of rotavirus

Answer 14

G1

Question 15

Pathogenesis of rotavirus

Answer 15

10 billion particles released in stool – malabsorptive diarrhea is the main issue (due to damage on the epithelial layer) – toxin NSP4 causes Ca2+ release

Question 16

How does rotavirus affect villi?

Answer 16

Causes villi blunting by making villi short – cannot absorb nutrients

Question 17

Diagnosis of rotavirus

Answer 17

EIA from stool sample (looking for antibodies), EM or RT-PCR less common

Question 18

Treatment of rotavirus

Answer 18

Oral rehydration therapy or IV rehydration therapy

Question 19

Prevention of rotavirus

Answer 19

Prevent fecal-oral transmission (sanitization and handwashing), IgA in colostrums (for nursing babies), vaccines

Question 20

Vaccine for rotavirus

Answer 20

2 live attenuated oral vaccines – Rotateq (reassorted human and bovine rotaviruses) and Rotatrix (human rotavirus) – recommended for infants

Question 21

Epidemiology of norovirus

Answer 21

Causes 96% outbreaks of nonbacterial gastroenteritis in US (foodborne illness), affects all age groups

Question 22

Pathology of norovirus

Answer 22

Causes malabsorption diarrhea, nausea, vomiting, and diarrhea within days, low grade fever (1/2 the time)

Question 23

Norovirus characteristics

Answer 23

Caliciviridae family, non-enveloped, +ssRNA genome, Norwalk virus founding member – prefers people with type A or O blood

Question 24

Tranmission of norovirus

Answer 24

Fecal-oral, person-to-person (close contact), fomites, waterborne, contaminated food

Question 25

Where do norovirus outbreaks occur?

Answer 25

Mostly in long-term care facilities, but also cruise ships, schools, hospitals, etc.

Question 26

Adenovirus characteristics

Answer 26

dsDNA genome, naked capsid, fiber protein at vertices – serotypes 40 and 41 cause gastroenteritis – no seasonal variation

Question 27

Diagnosis of adenovirus

Answer 27

Antibody-based

Question 28

Sapovirus

Answer 28

Causes gastroenteritis, Caliciviridea family member

Question 29

Astrovirus

Answer 29

Causes gastroenteritis, star-shaped, +ssRNA genome, infants/young children/elderly susceptible (also adults exposed to contaminated food/drink)