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23. Respiratory Viruses
Respiratory viruses
60
Microbiology
Undergraduate 1
11/19/2014

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Cards

Term
List some respiratory viruses!
Definition
- Influenza A, B
- Respiratory syncytial virus (RSV)
- Parainfluenza viruses (1-4)
- Adenovirus
- Rhinovirus
Term
What is the division between the upper and lower respiratory tract?
Definition
the larynx
Term
Why was there a significant drop in life expectancy in 1918 in the US and Canada?
Definition
There was an influenza pandemic
Term
What are some important characteristics of the influenza virus?
Definition
- single stranded
- RNA virus
- enveloped
- segmented genome
Term
Why is it significant that the influenza virus has a segmented genome?
Definition
Because if two strains infect a cell, they can swap genes and create a whole new strain
Term
There are really three influenza viruses: _, _ and _
Definition
A, B and C
but C tends to be unimportant
Term
When are influenza epidemics most common?
Definition
they happen on a yearly basis in the winter
Term
Which flu (Flu A, B or C) is most important and why?
Definition
- Because of its pandemic potential and because it is usually more severe
Term
How is influenza typically spread?
Definition
- droplets and on soiled hands
Term
What two important proteins are on the surface of the influenza virus?
Definition
-Hemagglutinin
- Neuraminidase
Term
What dose hemagglutinin do?
Definition
Sticks the virus to cell receptors
Term
What does neuraminidase do?
Definition
Frees the virus to infect other cells
Term
Explain DRIFTS
Definition
- Drifts are small changes/mutations that happen continuously over time as the virus replicates (remember than RNA polymerase is sloppy)
- This produces viruses that are different but related so they have similar antigenic properties
- So an immune system will typically respond if it is similar
- But if it changes enough the immune system will not respond
Term
What is the result of drifted viruses?
Definition
They contribute to epidemics and an excess number of deaths in the elderly and frail
Term
Explain what SHIFTS are.
Definition
- They are reassortments of avian and human viruses
- New viruses emerge with new-to-human proteins on their surfaces
Term
Drifts can occur in what kind of influenza? (as in a, b or c)
Definition
A and B
Term
Illustrate antigenic shift using the "swine flu"
Definition
- A duck is the avian host - often the virus is in the GI tract and gets picked up by animals such as pigs that get the duck poop on their noses.
- the virus replicates!
- the pig can recognize/be infected with both bird and human strains b/c it has two different receptors in its up respiratory tract
- The two viruses can mix (aka re-assort) and create a new virus which can then be transmitted to a human host
Term
Shifts occur in what kind of influenza? (as in A, B or C)
Definition
A
Term
In the twentieth century, the world experience three important influenza pandemics... what years, flu A subtype and common names?
Definition
1918- H1N1 --> Spanish flu
1957 - H2N2 --> Asian flu
1968 - H3N2 --> Hong Kong
Term
Since those three pandemics, the world experienced another in 2009 - name subtype and common name
Definition
H1N1 - swine flu
Term
How do you get influenza?
Definition
- droplet spread
- contaminated fingers/hands
- fomites
- aerosol (controversial)
Term
Explain the steps involved in the influenza-host interaction
Definition
- Influenza virus is inhaled
- Hemagglutinin activity glycoproteins on the surface of influenza virus attach to sialic acid on the surface of cells in the upper respiratory mucosa
- primary replication occurs in the lungs
- cytokines are released
Term
What happens when cytokines are released during the influenza-host interaction?
Definition
Cytokines prime surrounding cells by sending out a signal that says something is wrong

but over release of cytokines can lead to muscle aches, issues with the heart and other organs.

Cytokines are what make you feel like crap with the flu
Term
What is the stomach flu?
Definition
it doesn't exist

(unless the person is referring to norovirus... but even then apparently that shouldn't be called "The Flu")
Term
What are some lower respiratory tract complications associated with influenza?
Definition
- Croup and bronchiolitis (in kids) --> there is a direct viral effect, and kids tend to have narrower respiratory tracts
- Primary influenza pneumonia
Term
What are some secondary bacterial infection complications associated with influenza?
Definition
- pneumonia
- otitis media (remember it is often viral but in this case it's bacterial)
Term
What other complications can you have with influenza?
Definition
heart failure
Term
What patients get the most influenza complications/benefit most from vaccines?
Definition
- Elderly and children
- Chronic respiratory disease
- Chronic heart disease
- Immunosuppression
- Haematological disorders
- Chronic renal failure
- Diabetes mellitus
Term
Why are pregnant women at greater risk for flu?
Definition
They are pulmonary compromised! In pregnant women the fetus tends to press up against the diaphragm
And they are immunocompromised
Term
What groups of people (besides pregnant women) are at greater risk in flu pandemics?
Definition
- Aboriginal populations (environmental and genetic)
- Morbidly obese individuals
- Current smokers
Term
What type of vaccine is used for seasonal influenza?
Definition
Trivalent! 2 type A and 1 type B
Term
What kind of influenza vaccine are live attenuated?
Definition
the nasal spray form
- they are more expensive
Term
How efficacious are vaccines for influenza in
a) healthy young adults
b) elderly
c) preventing hospitalization and pneumonia?
Definition
a) 60-80%
b) 20-30%
c) 50-60%
Term
How protective are influenza vaccines?
Definition
- They are only good when they match with circulating viruses
- they are only good if you get re-vaccinated annually
Term
How do we treat influenza prophylactically?
Definition
We use neuraminidase inhibitors

- Osteltamivir --> influenza A and B
- Zamamivir --> influenza A and B
Term
How is zamamivir administered?
Definition
via a cumbersome inhaler
Term
Respiratory Syncytial virus is a ____.
Definition
paramyxovitus
Term
What is important about the RSV structure?
Definition
it is enveloped
Term
When do RSV epidemics occur?
Definition
- In the winter but also sporadic cases occur throughout the year
Term
How is RSV transmitted?
Definition
By hand contact

(less common: respiratory route)
Term
RSV is responsible for causing
____ in children and the
___ ___ in older kids/adults
Definition
bronchiolitis

common cold
Term
RSV may be fatal for certain children... which ones?
Definition
- Those who have heart and lung disease
- those who are premature
Term
Is RSV treatable?
Definition
yup
Term
What is Ribavirin used to treat?
Definition
It is used to treat severe infections
--> RSV

- note: it is expensive and requires hospitalization
Term
___ viruses are second only to RSV in infants and young children
Definition
Parainfluenza
Term
Parainluenza virus infections are often limited to which anatomical area?
Definition
the nasopharynx
Term
How common is croup with parainfluenza virus?
Definition
2% get it! It's formal name is laryngo-tracheo-bronchitis
Term
What is the classic sign on a x-ray with Croup?
Definition
The "steeple" sign - where there is narrowing of the tracheal air column at the larynx and distension of the hypo pharynx
Term
What type of virus is the adenovirus?
Definition
it is double stranded and naked (how risqué of you adenovirus) DNA virus
Term
How does Adenovirus get transmitted?
Definition
- Direct contact or respiratory droplets
Term
Adenovirus produces _-_% of pediatric respiratory infections
Definition
5-10%
Term
What are the clinical syndromes associated with adenovirus?
Definition
- Febrile pharyngitis
- Lower respiratory infections
- Pharyngoconjunctival fever
- Conjunctivitis
- Diarrhea
Term
What kind of virus is Rhinovirus?
Definition
- a picornavirus
-it is a positive strand RNA virus
Term
Where do we primarily see rhinovirus?
Definition
In upper airway:
- common cold and viral sinusitis
Term
On average, how many colds do children have per year?
Definition
2-8 per year!
Term
Who should be most concerned about enterovirus?
Definition
- asthmatics, immunocompromised people and children/babies
Term
What type of symptoms are a result of Enterovirus D68?
Definition
- mild to severe resp. illness
- fever, runny nose, sneezing, cough and body/muscle aches
Term
How common is enterovirus in adults?
Definition
It can be seen in adults... 25% of cases in past outbreaks
Term
How do we diagnose respiratory viral infections?
Definition
- Clinical syndromes
- Time of year
- What's going around in the community
- Virus isolation
- Virus antigen detection (but not with rhinovirus)
- Molecular methods (e.g. PCR)
- Serology (not common)
Term
How long do otherwise healthy people shed when they have been infected with influenza? What about immunocompromised patients?
Definition
5 to 7 days

weeks
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