Viral Pathogens - Cashdollar Flashcards
- Infections of what parts of the respiratory system are considered “upper respiratory infections”?
- Lower respiratory infections?
Following list is in order from proximal to distal
- Upper
- Sinusitis
- Common cold
- Pharyngitis
- Epiglottitis
- Laryngotracheitis
- Lower
- Bronchitis
- Bronchiolitis
- Pneumonia
Many respiratory viruses begin in the upper respiratory tract and some migrate to lower areas from there. Some viruses, however, can also spread into the blood, causing viremia and leading to systemic symptoms.
Name three types of respiratory viruses that are known to cause viremia.
- Measles virus
- Adenovirus
- Enteroviruses
Influenza Virus
- How many known subtypes of hemagglutinin (HA) are there?
- How many known subtypes of neuraminidase (NA) are there?
Influenza Virus
- 16 subtypes of HA
- 9 subtypes of NA
Influenza Virus
Describe the difference between antigenic drift and antigenic shift
Influenza Virus
- Antigenic drift: Small changes in the “recognizability” (serologic relatendess) of the virus over several years. Mediated by point mutations.
- Antigenic shift: Large changes in serologic relatedness within a single year. Mediated by reassortment of HA and NA subtypes between two viral strains within a doubly-infected host.
What are some important species of animal hosts of influenza?
- Aquatic Birds
- Pigs
- Poultry
- Cats
- Horses
- Dogs
- Aquatic Mammals
Name three influenza strains that have historically been repsonsible for major pandemics
- H1N1 (Spanish flu, Russian flu, Swine flu)
- H2N2 (Asian flu)
- H3N2 (Hong Kong flu)
What are two strains of avian influenza viruses that have been of recent concern regarding a possible pandemic in the future? Why are they a concern?
- H5N1
- H7N9
These two strains appear to cause severe symptoms and have a high mortality rate, although the limited data is skewed towards the severe cases, as they show up in hospitals.
Although these strains do not yet transmit easily between people, a future mutation could change allow for rapid transmission.
Influenza
- What cells does the influenza virus infect?
- How does the virus cause cellular damage?
- What is this celluar damage a risk for?
- Is viremia a major concern?
Influenza
- Ciliated epithelial cells lining the URT
- Lytic viral replication and the cytotoxic T-cell response cause epithelial destruction
- Epithelial destruction (both ciliated and mucus-secreting cells) disrupts the normal barrier and decreases clearance via the mucociliary escalator, increasing the risk of secondary bacterial infection
- Viremia does not play a major role in pathogenesis
If viremia is rare for influenza, how does it cause systemic symptoms beyond the respiratory tract?
The interferon and cytokine response to the virus cause the systemic symptoms.
Name three bacterial infections that occur secondary to influenza infection.
Of what concern are these secondary infections?
- Strep pneumo
- Staph aureus
- Haemophilus influenzae (HiB)
Secondary bacterial infections are the major cause of death in influenza
Name four rare complications of influenza.
- Myositis & cardiac involvement
- Guillain-Barré syndrome
- Encephalitis
- Reye’s syndrome
What two major forms of prevention and control of influenza infection? Name some specific examples
- Vaccines
- Formalin inactivated
- Attenuated infectious virus
- Intranasal
- Quadrivalent
- Antiviral drugs
- Amantadine & Rimantadine
- Zanamivir & Oseltamivir
Describe the mechanisms of action of:
- Amantadine & Rimantadine
- Zanamivir & Oseltamivir
Which set of drugs is not currently often used?
- A&R: Inhibit uncoating by blocking the M2 protein
- Not used - high degree of antiviral resistance
- Z&O: Neuraminidase inhibitors (inhibit release of progeny virus)
Rhinovirus
- What % of common colds are attributed to rhinovirus?
- How many major subtypes are there? How many individual serotypes?
- What other species act as a reservoir for rhinovirus?
Rhinovirus
- 50%
- 3 major, ~150 serotypes:
- RV-A (75 serotypes)
- RV-B (25)
- RV-C (51)
- Humans are the only natural host!
Rhinovirus
- How is rhinovirus transmitted?
- What is the course of the infection like?
- How can RV infection be prevented and controlled?
Rhinovirus
- Respiratory secretions
- Directly between individuals
- Fomites
- Mild, self-limiting infection
-
Prevention:
- No antivirals or vaccines available
- Handwashing
- Disinfectants
Enteroviruses
- When do these viruses often cause common colds?
- What preventative measures are available?
Enteroviruses
- Responsible for Summer colds and flu
- No vaccines or antivirals available - clean hands!
- Over just this past summer & fall, what specific strain of enterovirus has been of concern in the USA, including Wisconsin?
- How does this virus spread?
- Beyond mild to severe respiratory illness ,what are possible complications of this virus?
- EV-D68
- Respiratory secretions
- Complications:
-
Flaccid paralysis
- Several members of the EV family have been known to be a risk for paralytic disease in the past
- Difficulty breathing & wheezing
-
Flaccid paralysis