11 Viruses (3) Flashcards
What percent of all cases of human “gastroenteritis” are due to viruses?
~70%
Name the 4 main types of enteric viruses?
- Rotavirus
- Adenovirus
- Astrovirus
- Caliciviruses
Which of the 4 GI viruses are usually responsible for diarrhea in kids under 5 yrs?
Rotavirus
This GI virus mainly affects kids under 2 yrs.
Adenovirus
Who does the rotavirus usually affect? What symptom(s) often accompany it?
Kids under 5 yrs. It usually causes diarrhea in them.
Who is usually affected by the adenovirus?
Kids under 2 years
This GI virus usually affects ALL ages in the winter months.
Astrovirus
This GI virus usually affects ALL ages all year round.
Caliciviruses
All types of enteric viruses share two things in common:
- Mainly transmitted via FECAL-ORAL route
2. Disease progression is similar
How long does it take to first see the symptoms of enteric viruses?
1-3 days
Term for the period of time that it takes to see symptoms of a virus?
“incubation period”
Enteric viruses cause some common symptoms. Name 4.
- Vomiting
- Diarrhea
- Nausea
- Abdominal pain
In a healthy ind, for how long do enteric viruses usually infect their hosts?
3-4 days
Why is it difficult to tell which enteric virus an individual has just based on outward symptoms?
Because the symptoms associated w/ most types of enteric viruses are v. similar (i.e. they all cause diarrhea, vomiting, nausea, abdominal pain, etc.)
i.e. They all cause the same symptoms
A patient has more diarrhea than anything else. What kind of enteric virus does he have?
a. Rotavirus
b. Adenovirus
c. Astrovirus
d. Caliciviruses
e. Cannot tell from info given
e.
[ALL of them cause diarrhea. We need lab testing to tell which specific virus is involved]
Norovirus (aka. Norwalk virus) is part of what category of enteric viruses?
Calicivirus
What kind of virus is the norovirus? (i.e. nucleic acid type and naked/enveloped)
Naked RNA virus
How many infants and adults are infected by the norovirus each year in the US?
How many deaths does it cause each year?
Infants: 3.5 mill cases
Adults: 9.2 mill cases
Deaths: 30-50
What’s the usual source of norovirus?
Fecal-contaminated food/water
About how many virus particles of norovirus are needed to cause disease?
10-100 (very low infectious dose)
T or F: Norovirus-contaminated water has a characteristic odour, but looks completely normal.
F
It has no characteristic odour nor appearance
Most likely place for a norovirus outbreak to occur?
Long-term care facility
What defines an “outbreak” of norovirus?
> 2 confirmed cases linked by common exposure/location over a specific time period
Describe how noroviruses infect intestinal epithelial cells and cause the associated symptoms.
- Viruses attach to intestinal epithelial cells
- Viruses enter intestinal epithelial cells
- Viruses replicate in the intestinal epithelial cells
- Lytic infection cycle destroys host intestinal epithelial cells
- New viruses get released into FECES > re-transmission via oral-fecal route made possible
- Localized damage to gut epithelium > nausea, vomiting, abdominal pain, diarrhea (due to loss of absorptive ability)
Does long term, protective immunity develop after being infected w/ the norovirus?
No
Symptoms of norovirus are usually more severe in these two pops:
- V. young
2. V. old
How long does a norovirus cause diarrhea, vomiting, etc.?
1-5 days
What’s the main clinical concern of norovirus?
Severe dehydration
How can the dehydration that accompanies norovirus infections be mitigated?
- Fluid replacement
2. OTC oral rehydration salts
For how long after norovirus symptoms disappear can an ind remain infectious (i.e. continue to shed virus)?
2 weeks
Best way to avoid norovirus infection?
Maintain good hygeine
What 4 characteristics about the norovirus makes it a “perfect human pathogen”?
- Lots of new viruses are shed into the feces, even after symptoms have resolved
- Low infectious dose (i.e. easy to acquire)
- No long-term immunity
- Self-limiting; non-lethal > constant pool of new hosts
Viruses that infect the central nervous system are also called…
“neurotropic” viruses
Name three CNS diseases that can be caused by viruses that infect nerve cells.
- Encephalitis
- Meningitis
- Poliomyelitis
List two CNS viruses:
- West Nile virus
2. Zika virus
What kind of virus is the West Nile virus?
Small, enveloped RNA virus
What do we call a virus which can be transferred via a living carrier?
Vector-borne virus
West Nile virus is endemic to…
- Africa
- West Asia
- Middle East
When did the first North American outbreak of West Nile Virus occur?
1999
What animal is the natural host for West Nile viruses?
Birds (crows, specifically)
What is the main transmission cycle through which birds get infected w/ West Nile virus?
bird > mosquito > bird
T or F: It’s impossible for West Nile virus to be spread from human to human.
F
It can be spread during birth, organ transplants, or blood transfusions.
What does it mean for humans to be a “dead-end” host wrt West Nile viruses?
Humans cannot infect other humans via mosquito bites
T or F: West Nile virus can be transferred b/w humans via casual contact.
F
Must directly exchange blood for transmission of virus to occur
Humans are “_____” hosts of West Nile virus because they aren’t the ‘intended’ targets for the bite
incidental
About how many West Nile-infected ppl have NO symptoms?
~80% (!!)
T or F: Inds who develop West Nile fever do not recover.
F
Recovery usually occurs after 3-4 days
How many ppl develop West Nile fever?
20%
About 1% of pts with West Nile virus develop this.
Severe encephalitis
How is Zika virus transmitted?
mosquitoes
Who is affected the most by Zika virus infections?
Pregnant women
Why are Zika virus infections dangerous in pregnant women?
There’s an increased risk of fetal malformations (microcephaly, specifically)
What’re “blood-borne” viruses?
Viruses that infect various organs/tissues/cells, but whose presence can routinely be seen in the bloodstream
How’re blood-borne viruses transmitted?
Direct contact w/ the blood OR bodily fluids
What are the major blood-borne viruses?
- Hep B
- Hep C
- HIV
What are the minor blood-borne viruses?
- Hep A
- Hep D
- West Nile Virus
- Cytomegalovirus
“Hepatitis” indicates…
inflammation of the liver
Name some symptoms of being infected w/ Hepatitis C (5)
- Jaundice
- Poor appetite
- Weight loss
- Fatigue
- Muscle and joint pain
T or F: Hepatitis can be caused by other factors besides the hepatitis C virus
T
Approx how many ppl across the world are infected w/ Hep C virus?
170-200 million ppl worldwide
Hep C (HCV) is a(n) _____ virus
a. enveloped
b. naked
c. DNA
d. RNA
e. both a and c
f. both a and d
g. both b and c
h. both b and d
f.
HCV: Enveloped RNA virus
How many genes comprises the HCV genome?
10 genes
What’s the replication rate of HCV?
Up to 10^12 new viruses produced per day in an active infection
There’re 7 different “genotypes” associated w/ HCVs. What part of the HCV genome differs amongst HCVs?
They differ in the sequence of “non-structural” genes
HCV genotypes tell us two things about these viruses:
- Geographic distribution
2. How they’ll respond to therapy
What’re four common ways for HCV to be transmitted?
- IV drug use w/ shared needles (65%!)
- Blood transfusion/organ transplants
- Occupational exposure to blood
- Hemodialysis
Which of the following represent other ways HCV can be transmitted?
a. Cough droplets being inhaled
b. Mosquitoes
c. Mother to fetus transmission
d. Sharing eating utensils
e. Unprotected sex
f. Tattooing/body piercing w/ improperly sterilized equipment
c, e, f
During the acute HCV infection phase, when do symptoms of hepatitis usually appear (for the 30% who actually show symptoms)?
7-8 weeks
What percentage of ppl w/ HCV eliminate the virus?
20%
What percentage of ppl w/ HCV progress to a “chronic” infection?
80%
How long must a person be suffering from an HCV infection before they’re considered “chronic”?
> 6 months
For inds w/ chronic HCV infections, what percentage develops liver disease w/ mild or no symptoms?
~70%
For inds w/ chronic HCV infections, what percentage experiences severe cirrhosis and liver failure?
~25%
For inds w/ chronic HCV infections, what percentage goes on to develop liver cancer (hepatocellular carcinoma)?
~3%
Why do different pts take varying amts of times (sometimes even decades!) to develop cirrhosis or cancer of the liver due to HCV?
Bc other factors are often involved in the development of liver cirrhosis and cancer (e.g. alcoholism, other infections, etc.)
If a patient has antibodies against HCV (found using serology tests), then this means…
a. pt has an active disease
b. pt HAD a disease
c. not enough info to determine presence of disease state
c.
If a patient has antibodies against HCV (found using serology tests) and HCV RNA is found in his liver cells (found using nucleic acid amplification tests - PCR), then this means…
a. pt has an active disease
b. pt HAD a disease
c. not enough info to determine presence of disease state
a.
T or F: HCV is an example of a virus for which no anti-viral medications exist.
F
It’s actually one of the few viruses for which effective anti-virals exist.
What was the treatment of choice for HCV pre-2011?
And were four probs w/ it?
inteferon (non-specific anti-viral action) + ribavirin (inhibits virus replication)
Four probs:
- Inconvenient dosing
- Long treatment times
- Costly
- 35-50% response rate
What parts of the viral life cycle do many new drugs for HCV target?
- HCV replication and/or…
2. HCV assembly
What is Harvoni (TM) used for? What part of the viral life cycle does it block?
It’s an anti-viral that’s used in the treatment of HCV.
It blocks viral replication
Why is there no preventative vaccine to date for HCV?
- Numerous genotypes and sub-types of HCV
2. No suitable animal models for testing
Why is HCV known as the “Silent Epidemic”
Bc 70% of inds w/ HCV don’t show any obvious symptoms
Who should be tested for HCV (even if they don’t show symptoms)?
50-70 year olds
