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Flashcards in Viral Pathogens - Cashdollar Deck (43)
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  1. Infections of what parts of the respiratory system are considered "upper respiratory infections"?
  2. 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.

  1. Measles virus
  2. Adenovirus
  3. 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 shiftLarge 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. 



  1. What cells does the influenza virus infect?
  2. How does the virus cause cellular damage?
  3. What is this celluar damage a risk for?
  4. Is viremia a major concern?


  1. Ciliated epithelial cells lining the URT
  2. Lytic viral replication and the cytotoxic T-cell response cause epithelial destruction
  3. 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
  4. 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?

  1. Strep pneumo
  2. Staph aureus
  3. Haemophilus influenzae (HiB)

Secondary bacterial infections are the major cause of death in influenza


Name four rare complications of influenza.

  1. Myositis & cardiac involvement
  2. Guillain-Barré syndrome
  3. Encephalitis
  4. Reye's syndrome


What two major forms of prevention and control of influenza infection? Name some specific examples

  1. Vaccines
    • Formalin inactivated
    • Attenuated infectious virus
      • Intranasal
    • Quadrivalent
  2. Antiviral drugs
    • Amantadine & Rimantadine
    • Zanamivir & Oseltamivir


Describe the mechanisms of action of:

  1. Amantadine & Rimantadine
  2. Zanamivir & Oseltamivir

Which set of drugs is not currently often used?

  1. A&R: Inhibit uncoating by blocking the M2 protein
    • Not used - high degree of antiviral resistance
  2. Z&O: Neuraminidase inhibitors (inhibit release of progeny virus)





  1. What % of common colds are attributed to rhinovirus?
  2. How many major subtypes are there? How many individual serotypes?
  3. What other species act as a reservoir for rhinovirus?


  1. 50%
  2. 3 major, ~150 serotypes:
    • RV-A (75 serotypes)
    • RV-B (25)
    • RV-C (51)
  3. Humans are the only natural host!



  1. How is rhinovirus transmitted?
  2. What is the course of the infection like?
  3. How can RV infection be prevented and controlled?


  1. Respiratory secretions
    • Directly between individuals
    • Fomites
  2. Mild, self-limiting infection
  3. Prevention:
    • No antivirals or vaccines available
    • Handwashing
    • Disinfectants



  1. When do these viruses often cause common colds?
  2. What preventative measures are available?


  1. Responsible for Summer colds and flu
  2. No vaccines or antivirals available - clean hands!


  1. Over just this past summer & fall, what specific strain of enterovirus has been of concern in the USA, including Wisconsin?
  2. How does this virus spread?
  3. Beyond mild to severe respiratory illness ,what are possible complications of this virus?

  1. EV-D68
  2. Respiratory secretions
  3. 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



  1. What % of common colds are attributed to coronaviruses?
  2. What part of the respiratory tract is infected?
  3. What preventative measures are there?


  1. 10-15% (second most common cause)
  2. Limited to upper RT
    • Exception has been seen with severe cases of MERS-CoV - Lower RT affected
  3. No vaccines or antivirals available - containment measures (containment of animal reservoirs, hygiene, etc.)


What two types of coronavirus have been responsible for serious illnesses over the past decade? What important animal reservoirs are there for these viruses?

  1. SARS outbreak: SARS-CoV
    • Animal: bats
  2. Acute pneumonia & renal failure: MERS-CoV
    • Animals: bats & camels

N.B. Currently, MERS-CoV does not appear to readily transmit from person to person. A mutation resulting in a more transmissable strain is a major concern.


Parainfluenza Viruses

  1. When do infections typically occur?
  2. What is a major concern in infants and young children?
  3. Is a vaccine available?

Parainfluenza Viruses

  1. Fall & Winter
  2. Croup (subglottal swelling may close airway)
  3. No vaccine


Parainfluenza Viruses

Describe the diseases caused by Types 1-4 of parainfluenza virus.

Parainfluenza Viruses

  • Types 1 & 2: Common cause of croup
  • Type 3: Similar to RSV, as it causes bronchiolitis in infants
  • Type 4: Usually mild disease


  1. What is croup?
  2. Describe the typical presentation of croup.

  1. Croup: aka laryngotracheobronchitis. Inflammation around the larynx & vocal cords. Can cause respiratory distress.
  2. Presentation:
    • Poor appetite
    • Sore throat
    • Fever
    • Hoarse voice
    • Barking seal cough
    • Stridor (high-pitched noise with inspiration)
    • Respiratory distress symptoms
      • e.g. nasal flaring


Respiratory Syncytial Virus

  1. How does it get its name?
  2. How prevalent is it?
  3. When and where are outbreaks seen?
  4. Are reinfections common?
  5. Is there a vaccine? Antivirals?

Respiratory Syncytial Virus

  1. Virus causes fusion of infected cells into multinucleated syncytia
  2. Infects virtually everyone by age 2
  3. Outbreak during winter months in temperate climates (assumably from close quarters/indoors)
  4. No - infections possible throughout life. Can be severe in the elderly
  5. No vaccine, but antivirals helpful in cases where required



How does an active RSV infection present in each of the following age groups?

  1. Children < 1 yr
  2. Children
  3. "Older children" & adults


  1. <1 yr: Bronchiolitis, pneumonia, or both
  2. Children: Febrile rhinitis & pharyngitis
  3. Older Child / Adult: Common cold

(Milder with age)



How is symptomatic RSV infection treated in each of the following cases?

  1. Otherwise healthy infant
  2. Premature infant
  3. Immunocompromised infant

  1. Healthy:
    • Supportive treatment
      • O2
      • IV fluids
      • nebulized cold steam
  2. Premature:
    • Aerosolized ribavirin
    • Passive immunization with anti-RSV Ig & human mAbs
  3. Immunocompromised:
    • Aerosolized ribavirin
    • anti-RSV Ig / mAbs will not work - deficient immune system cannot use the Abs



  1. How does it present?
  2. In what populations is severe disease seen?
  3. How is it diagnosed?
  4. How prevalent is it?
  5. Are vaccines or antivirals available?


  1. Similar to RSV but milder
  2. Infants, elderly, & immunocompromised
  3. Use RT-PCR to definitely diagnose
  4. Almost all children seropositive by age 5
  5. No vaccine, no antivirals


Hendra and Nipah Viruses

  1. Why are these two emerging respiratory viruses a concern?
  2. Where have human cases occured?
  3. What are the important animal sources?

Hendra and Nipah Viruses

  1. High mortality rates!
  2. Australia & Asia
  3. Bats originally, Pigs as intermediate



  1. What types of disease does it cause?
  2. What three adenoviruses have been associated with particularly severe respiratory symptoms?
  3. What is seen in these cases?


  1. Wide spectrum of diseases (single virus does not usually cause all diseases - they have varying tissue tropism):
    • Respiratory infection
    • Conjunctivitis
    • GI infections
    • Hemorrhagic cystitis
  2. Severe types: Adenoviruses 4, 7, and 14
  3. Acute & sometimes serious respiratory disease. Pneumonia in severe cases.



  • What types of respiratory infection are caused by adenoviruses in reference to viral life cycle?
  • When is systemic disease seen?


Can cause:

  • Acute
  • Persistent (w/ viral shedding)
  • Latent

Systemic disease in the immunocompromised



  1. Is a vaccine available?
  2. Antiviral therapy?


  1. Live attenuated vaccine available for military recruits
    • None available for general public
  2. Cidofovir can be used to treat severe infections in the immunocompromised

Decks in M2 Renal/Respiratory Class (50):