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MCIM 223 > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

Gastrointestinal (“Enteric”) Viruses

A
  • 70% of gastroenteritis is virus caused (30% bacterial/ parasitic)
    1. Mostly transmitted by fecal - oral
  1. Disease progression is similar
    - Symptoms 1-3 days after 1st contact
    - similar symptoms (vomiting, diarrhea, nausea, abdominal pain)
    - Self-limiting infection (3-4 days) in healthy humans

determining which virus gi disease can only be done in lab

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2
Q

4 types of enteric viruses responsible for most diseases

A

Rotavirus - diarrhea in kids under 5 (in adults with minor symptoms) (year round/ mostly winter)

Adenovirus - kids under 2 (year round)

Astrovirus- all ages (winter)

Calicviruses (large group/ norovirus) - All ages/ year round

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3
Q

Norovirus (Norwalk Virus)

A

Naked RNA virus
Found in Norwalk, ohio (viruses with similar features called Norwalk-like)

Fecal-contaminated food/water = source

  • cant tell by looking/smelling
  • low infectious dose (10-100 virus particles can cause disease)
  • Close contact for extended periods = risk (care home[59% causes] , hospitals, day care, cruise)

-300 to 400 outbreaks per year in Canada mostly winter

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4
Q

What defines an outbreak of norovirus

A

-more than 2 cases linked by common exposure/location over <6 days

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5
Q

How does Norovirus cause disease

A
  • Viruses attach, enter and replicate in intestinal epithelial cells
  • lytic infection cycle destroys cells
  • new viruses released into feces (re-transmission)
  • Localized dmg to gut epithelium (nausea, vomiting, pain, loss of absorptive capacity (diarrhea)
  • Self limiting infection (recovery via immune response but no protective immunity)
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6
Q

Clinical features of Norovirus

A
  • 2 to 3 days incubation period before symptoms seen
  • 1 to 5 days of diarrhea, nausea, vomiting, abd. pain. (severe in very young/old)
  • Severe dehydration is main concern
  • tachycardia
  • hypotension
  • Supportive therapy only (anti virals don’t work)
  • fluid replacement/ oral rehydration salts (Na, K, Glucose)

-Shed viruses after 2 weeks of no symptoms (good hygiene important)

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7
Q

Viruses of the Central Nervous System

(Neurotropic viruses diseases) 3

A
  • Encephalitis (inflammation of the brain)
  • meningitis (inflammation of protective membrane covering brain)
  • Poliomyelitis (destruction of motor neurons in brain, spine)
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8
Q

(Neurotropic viruses)

A

Viruses =Mumps, measles, rabies, herpes, enteroviruses, polio

Infection usually starts elsewhere (fecal to neurons)

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9
Q

West Nile Virus (WNV)(neurotropic disease)

A
  • small enveloped RNA virus
  • Vector borne virus (living carrier)
  • Uganda, remained localized to Africa, West Asia, middle east
  • 1st outbreak in new York (middle east strain)
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10
Q

West Nile Virus Transmission cycle

A

-natural host is birds (mostly crow)

Primary transmission cycle is from bird to bird via mosquito

Humans (other animals) are incidental host (bug bite that leads to dead end)
-not enough virus in human blood to re-transmit

Cant transmit through casual contact (only through organ transplants, blood transfusion, childbirth)

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11
Q

WNV Clinical Presentation

A

80% no symptoms
20 % = West nile fever

  • 3 to 14 days after bite
  • fever, headache, body ache, rash, swollen glands
  • lasts 3 - 4 days then recover with no later effects
  • No anti-therapy/ no human vaccine
  • Unknown if protective immunity develops
  • avoid mosquitos
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12
Q

1% = encephalitis of WNV

A

Replication in brain
-Headache, high fever, neck stiffness, disorientation, paralysis, seizures

Neurological dmg permanent, symptoms disappear

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13
Q

Blood Borne Viruses

A

Infect various organs, but presence is detected in bloodstream/bodily fluids

Transmitted by direct contact with fluid

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14
Q

Major BBV

Minor BBV

Health care Worry

A

Major: Hep B, Hep C, HIV

Minor: Hep A, D, WNV, cytomegalovirus

Hep B = 1 in 3 risk of infection
Hep C = 1 in 30
HIV = 1 in 300

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15
Q

Hepatitis C Virus

A

Hepatitis = inflammation of liver
-Jaundice, poor appetite, weight loss, fatigue, muscle and joint paint

-Progressive loss of liver function, often requiring liver transplants to avoid death (liver transplants 40% due to Hep C)

First called non-a/b

Enveloped RNA Virus (small genome/10 genes)
Rapid Replication (10^12/day)
7 different genotypes (plus >50 subtypes) (DIFFER IN SEQUENCE OF NON-STRUCTURAL GENES)

differ in how well they respond to therapy and are distributed differently throughout the world (eg. North America – Geno. 1; Middle East & Africa – Geno. 4)

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16
Q

Transmission of HCV

A

Blood borne ( shared needles 65%, exposure, hemodialysis, blood transfusion/ transplant <0.1%

  • Household exposure or unprotected sex with HCV+ partner
  • Mother fetus transmission

NOT TRANSMITTED BY CASUAL CONTACT:
-Coughing, sneezing, hugging, kissing, Sharing eating utensils or via food or water, biting insects

17
Q

Progression of Clinical disease (after first contact)

A

HC -> blood -> liver
Acute infection = 7-8 weeks 30% see symptoms,/70% don’t see symptoms (20% no further symptoms)

80% of acute -> chronic

  • > 6 months
  • Rate of virus replication slows & severity of symptoms declines

Progression to cirrhosis &/or cancer can take decades (many factors)

18
Q

In the chronically infected population (HCV)

A

≈ 70% develop liver disease with mild or no symptoms
→ ≈ 25% develop more severe cirrhosis (scarring) of liver + liver failure
→ ≈ 3% develop liver cancer (hepatocelluar carcinoma)

19
Q

Diagnosis of HCV via a blood test:

A

Antibodies against HCV (serology)
(Positive = acute or chronic disease or past exposure to the virus)

HCV nucleic acid amplification test (PCR)
(Positive = virus is present & therefore patient has active disease)

20
Q

Anti-viral therapy for HCV

A

Virus has effective anti-virals

Interferon = non-specific anti viral
Ribavirin = inhibit replication in cell

Inconvenient dosage/ 3 inject 3 subcutaneous and 2 daily ribavirin

costly

21
Q

New HCV anti-virals

A

Harvoni = 2 compounds (Ledipasvir + Sofosbuvir) Block viral replication \
One pill per day, mild side effects
>90 response rate

22
Q

Can HCV be prevented or cured

A

No preventative vaccine to date

  • Numerous genotypes & sub-types
  • Cant do animal ttesing

“Cure” = no virus after 24 weeks

  Cure rate after treatment with new anti-virals ≈ 75-95

   Success rate for cure depends on:

- Overall health of patient - Genotype of the virus (geno. 1 is harder to treat)
- Patient compliance with dosing instructions
23
Q

Why is HCV silent epidemic

A

Lack of obvious symptoms in many people (70% of those infected don’t know it)

Risk of long-term liver damage even without prior obvious symptoms

Encourage testing for HCV in 50-70 yr old age group (increase awareness)

MCIM 223 (21 decks)

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