B3.006 Prework 1 Influenza Virus

Question 1

describe the physical features of the influenza virus

Answer 1

ssRNA, enveloped
helical nucleocapsid
8 segment genome

Question 2

viral family of influenza

Answer 2

orthomyxoviridae

influenza A, B surface antigens

Question 3

hemagglutinin function on surface of influenza virus

Answer 3

binds sialic acid/ promotes viral entry into host cell

Question 4

neuraminidase function on surface of influenza virus

Answer 4

promotes progeny virion release

Question 5

how are influenza epidemics classified

Answer 5

associated with excess morbidity and mortality

usually in form of increased rates of pneumonia and influenza associated hospitalizations and deaths

Question 6

antigenic drift

Answer 6

minor antigenic changes based on random mutations of hemagglutinin or neuraminidase genes
cause epidemics

Question 7

antigenic shift

Answer 7

reassortment of viral genome segments
viruses are new viruses to which the population has no immunity
lead to pandemics, more deadly

Question 8

pandemic influenza

Answer 8

severe outbreak that rapidly progress to involve all parts of the world
associated with emergence of new virus
characterized by higher attack rate, different age distribution, occur outside usual window of seasonality, multiple waves

Question 9

why was the swine flu epidemic of 2009-2010 unique in the affected population?

Answer 9

young and otherwise healthy individuals were affected at greater rates
elderly likely exposed to a different H1N1 strain during a previous pandemic and had some immunity

Question 10

how does the influenza virus attack a host?

Answer 10

virus is deposited on the respiratory tract epithelium and attaches to and penetrates columnar epithelial cells

Question 11

what normally prevents influenza attachment?

Answer 11

specific secretory antibody (IgA)
nonspecific mucoproteins
mechanical action of mucociliary apparatus

Question 12

what happens after the adsorption of the flu virus?

Answer 12

virus replication begins and leads to cell death through necrosis/apoptosis
virus release initiates infection of adjacent cells

Question 13

flu incubation time

Answer 13

1-4 days

Question 14

flu illness duration

Answer 14

2-5 days if uncomplicated (without pneumonia or secondary bacterial infection)

Question 15

how long can viral shedding occur w the flu?

Answer 15

starts 1 day before symptoms and lasts for 6 days total

Question 16

how is the flu transmitted?

Answer 16

large droplets

requires close contact (large droplets can only travel 6 ft)

Question 17

clinical symptoms common of the flu

Answer 17

fever
chills
headaches
myalgias (extremities, back, calves in children)
malaise
anorexia
respiratory symptoms

Question 18

pulmonary complications associated with influenza

Answer 18

primary influenza viral pneumonia
pneumonia secondary to bacterial infection
croup
COPD exacerbation

Question 19

non-pulmonary complications associated with influenza

Answer 19

myositis (mostly children)
cardiac toxic shock syndrome
Guillain-Barre (flu A)
transverse myelitis
encephalitis
Reye Syndrome (w use of aspirin in kids)

Question 20

RT-PCR flu diagnostic test

Answer 20

high sensitivity and very high specificity
highly recommended
can differentiate between A and B subtypes
1-24 hrs

Question 21

rapid antigen detection flu diagnostic test

Answer 21

sensitivity around 62%
specificity around 98%
high false negative rate
some tests can distinguish between A and B subtypes
10-20 min
used in ER and primary care settings

Question 22

shell viral culture flu diagnostic test

Answer 22

moderately high sensitivity
highest specificity
can confirm screening test results
not useful for timely clinical management
48-72 hours

Question 23

serologic tests for flu diagnostics

Answer 23

available only in reference labs
not useful for clinical management
retrospective diagnosis, surveillance, or research

Question 24

why is early antiviral treatment important with regards to the flu?

Answer 24

can shorted duration of fever and illness symptoms
may reduce risk of complications
reduce death in hospitalized patients
shorten duration of hospitalization
clinical benefit is greatest when administered early (within 48 hours)

Question 25

to whom is antiviral treatment recommended when they are confirmed/suspected of having the flu?

Answer 25

hospitalized patients
severe, complicated or progressive illness
high risk for complications

Question 26

2 classes of anti-influenza chemotherapy

Answer 26

inhibitors of uncoating (block M2)

neuraminidase inhibitors

Question 27

drug inhibitors of uncoating

Answer 27

rimantadine

amantidine

Question 28

mechanism of rimantadine/amantidine

Answer 28

blocks viral uncoating by blocking M2 proton channel
administered orally
treats influenza A
GI intolerance, CNS effects (only rimantadine)

Question 29

viral neuraminidase inhibitors

Answer 29

oseltamivir (Tamiflu)
zanamivir (Relenza)
peramivir (Rapivab)

Question 30

mechanism of oseltamivir

Answer 30

pro-drug
activated in gut and liver to inhibit the functioning of the flu virus neuraminidase
administered PO
treats A and B
well tolerated, some nausea and vomiting

Question 31

mechanism of zanamivir

Answer 31

inhaled drug
inhibits neuraminidase
treats A and B
bronchospasm in asthmatics, nausea, diarrhea

Question 32

mechanism of peramivir

Answer 32

administered IV
inhibits neuraminidase
treats A and B
can cause diarrhea

Question 33

influenza prophylaxis (ppx)

Answer 33

not a substitute for vaccination

consider if you have close contact to a person w the flu and a high risk for complication

Question 34

who has a high risk for complications of the flu?

Answer 34

chronic pulmonary/ cardiovascular disease (except hypertension)
penal dysfunction
hemoglobinopathies
immunodeficiency
neurologic conditions that compromise handling of respiratory secretions
HIV
pregnant women or within 2 weeks of delivery
kids <5
children <19 on aspirin
patients in nursing homes
morbid obesity
native americans and Alaska natives