AuCoin > Influenza & Viral Pneumonia Flashcards
what causes the inflammation in pneumonia?
infection w/ virus/bacteria
AND
immune response to infection
what is primarily affected in pneumonia?
the alveoli
who is most likely to get viral pneumonia?
young kids
oldies
WHY are the 2 age groups susceptible to viral pneumonia?
young kids have NAIVE immune systems
oldies have WEAK immune systems
what are the typical sx of pneumonia?
cough
fever
chills
SOB
what are the 3 common causes of viral pneumonia?
- influenza virus A & B
- RSV
- human parainfluenza virus
what are the 4 LESS common causes of viral pneumonia?
- adenoviruses
- rhinoviruses
- metapneumovirus
- SARS
which 5 viruses cause other diseases & MAY cause pneumonia?
- HSV
- VZV
- Measles
- Rubella
- CMV
what 2 pulmonary defense mechanisms prevent introduction of particulate matter in the lower airway?
epiglottis
cough reflex
what things work in the alveoli to defend against lower respiratory tract infections?
cell-mediated immunity
humoral factors
inflammatory response
which Ig plays a role in mucosal immunity?
IgA
more IgA is produced in mucosal linings than all other ab combined
what secretes mucin?
goblet cells
what does mucin do?
dissolves in water to form mucus
what type of cells are goblet cells?
glandular simple columnar epithelium
what type of virus is an orthomyxo virus?
(-) RNA
w/ envelope
how does an influenza pandemic occur?
a variant of influenza A w/ a new hemagglutinin that ppl don’t have pre-existing ab to is introduced into the pop
how is influenza transmitted?
respiratory droplets
which strain of influenza causes pandemics?
A
which strain of influenza causes outbreaks?
B
which strain of influenza causes milder infections?
C
how many types of hemagglutinin (HA) & neuraminidase (NA) are there in influenza A virus?
16 ag types of HA
9 types of NA
what is antigenic SHIFT?
REASSORTMENT of segments of the genome RNA
what is antigenic DRIFT?
small MUTATIONS in the genome RNA
antigenic changes to WHAT cause epidemics & pandemics?
HA & NA
hemagglutinin & neuraminidase
how long is the incubation period for influenza?
24-48 hours
T/F: influenza virus is an orthomyxovirus
TRUE
what happens after the incubation period of influenza virus?
SUDDEN SX: fever myalgia HA sore throat cough
who is at high risk of developing influenza virus infection?
elderly pts
pts w/ cardiac or pulmonary disease
how long does it take for influenza sx to resolve?
4-7 days
what can complicate the course of influenza?
pneumonia
what does immunity to influenza depend on?
secretory IgA targeting HA (hemagglutinin) in the respiratory tract
how do you dx influenza?
clinical grounds
lab tests are avail
what are the RXes for treatment AND prevention of influenza?
oseltamivir (tamiflu)
zanamivir (relenza)
what is the prevention of influenza based on?
vaccine
what does the influenza virus vaccine contain?
influenza A & B viruses
what happens to the influenza vax yearly?
it is reformulated to the current ag strains
how do relenza & tamiflu work?
neuraminidase inhibitors > inhibit the release of virus from infected cells
what is responsible for more than HALF of all acute illnesses each year in the US (general)?
respiratory illnesses
when does influenza circulate in the US?
fall & early spring
why is influenza hard to control?
MUTABILITY &
high frequency of REASSORTMENT
(so basically drift & shift)
which one is antigenically variable: influenza A, B, or C?
A
which one causes the majority of disease: influenza A, B, or C?
A
which strain is antigenically stable: A, B, or C?
C
which strain has intermediate antigenic changes: A, B, or C?
B
which strain can infect aquatic birds, chickens, ducks, & pigs?
A
where are HA & NA located on the virus?
surface (they’re glycoproteins)
what are the 7 steps of influenza virus replication? (this is a long one)
- receptor-mediated endocytosis
- release segmented RNPs into cytoplasm
- transport genome into nucleus
- replication & transcription
- transport viral mRNAs to cytoplasm for translation
- transport early viral replication proteins back to nucleus
- assembly & budding at plasma membrane
what receptor mediates the endocytosis of influenza?
sialic acid receptor
why is influenza virus unusual among RNA viruses?
because RNA transcription and replication occur in the NUCLEUS
what does the low pH of the endosome allow?
membrane fusion & release of the viral RNPs in the cytosol
what happens shortly after infection?
host cell protein synthesis is shut OFF
what is RNA polymerase composed of?
3 viral P proteins
what does RNA polymerase do?
transcription > produces a (+) sense mRNA from the (-) sense RNA genome
what purpose does the (+) sense mRNA serve?
translated to viral proteins
AND
used as a template to make viral (-) sense RNA genomes
how is a RNP formed?
nucleoprotein (NP) associates w/ viral RNA
what 3 encoded proteins are bound to the viral NP?
PA
PB1
PB2
(pennsylvania peanut butter)
what do PA, PB1, & PB2 do?
RNA transcription & replication
what forms a shell below the viral membrane which is important in particle assembly?
M1
matrix protein
what surrounds the viral particle derived from the plasma membrane of the host cell?
lipid envelope
what gets inserted into the envelope of orthomyxoviruses?
hemagglutinin & neuraminidase
T/F: HA & NA are embedded into the surface of the virus so that they don’t protrude
FALSE
they are exposed as SPIKES
what do NA & HA determine?
antigenic variation of influenza viruses
T/F: 2 distinct influenza viruses may infect a single host cell
TRUE
when 2 distinct influenza viruses infect a cell, what happens?
the RNA genomes are shuffled so you get a NEW influenza virus (REASSORTMENT)
what is the consequence of RNA mixing from 2 diff influenza viruses?
sudden CHANGE in viral SURFACE ANTIGENS
why is it a challenge to produce only 1 influenza vax?
bc if 2 distinct influenza viruses infect a cell, the RNA genomes reassort & change their stupid surface antigens
what do you use to divide influenza viruses into A, B, & C?
antigenic diffs btwn NUCLEOCAPSID (NP) & MATRIX (M) proteins
what are the 2 internal structural proteins that determine ag diffs?
nucleocapsid (NP)
matrix (M)
what is used to subtype the influenza viruses?
ag variation among surface glycoproteins HA & NA
what is the nomenclature system for orthomyxoviruses?
type host of origin geo origin strain # year of isolation HA & NA subtype (example: A/swine/Iowa/15/30(H1N1) )
if the orthomyxovirus has a host origin in humans, do you put that in the nomenclature?
nope
do nucleocapsid & matrix proteins drift MORE OR LESS than the glycoproteins (HA & NA)?
LESS
how many subtypes of HA are there?
15
how many subtypes of NA are there?
9
what species are the HA & NA subtypes in diff combos isolated in?
birds
animals
humans
how many HA & NA subtypes have been recovered from humans?
4 HA (1 2 3 & 5) 2 NA (1 & 2)
what is tropism?
HA protein of influenza binds virus particles to susceptible cells
what is the major ag on flu that neutralizing ab are directed against?
HA
what is primarily responsible for the continual evolution of new strains & subsequent influenza epidemics?
variability of HA
when does NA function?
at the END of the viral replication cycle
what does NA facilitate?
the release of viral particles from infected cell surface during the budding process
antigenic variants have a (BLANK) over parental virus in the presence of ab directed against the original strain
selective advantage
what are MINOR ag changes considered?
antigenic DRIFT
what are major changes in HA & NA termed?
antigenic SHIFT (bc they form new subtypes via reassortment)
what does antigenic shift reflect?
drastic changes in the sequence of viral glycoproteins
what is antigenic drift due to?
accumulation of POINT MUTATIONS in the gene
what can alter antigenic sites on glycoproteins?
sequence changes
what is the mechanism for the shift of orthomyxoviruses?
genetic reassortment btwn human & avian influenza viruses
how does influenza virus spread?
from person to person via airborne droplets or by contact w/ contaminated surfaces
which cells get infected w/ orthomyxoviruses?
respiratory epithelial cells
what happens to the cells that get infected w/ orthomyxoviruses?
they are killed
then the virus spreads to other cells
what is the explanation for the incubation period of influenza?
viral dose
host immune system
what is detectable in respiratory secretions ~1 day post-infection?
interferon
what is detectable in 1-2
ab & cell mediated immunity
T/F: resistance to secondary bacterial infections is common
TRUE
bc cellular destruction is widespread
(resistance to staph, strep, H. flu)
who should get the influenza vax?
anyone over 6 mo
ANNUALLY
what 3 kinds of flu viruses commonly circulate among people today?
- influenza A (H1N1) viruses
- influenza A (H3N2) viruses
- influenza B viruses
which strains are included in the 2014-2015 trivalent flu vax?
A/California/7/2009 (H1N1) pdm09-like virus
A/Texas/50/2012 (H3N2)-like virus
B/Massachusetts/2/2012-like virus
some also protects against addn’l B/Brisbane/60/2008-like virus
what indicates a highly pathogenic avian influenza?
H5 or H7 surface protein
what are most common flu deaths d/t?
opportunistic infections (like bacterial pneumonia)
what flu strain can kill pts w/o secondary opportunistic infection?
H5N1
T/F: RSV is an orthomyxovirus
FALSE
it’s a PARAmyxovirus
what is the most common cause of pneumonia & bronchitis in infants?
RSV
who is susceptible to RSV?
neonates
preemies
babies w/ cardiopulmonary diseases
how is RSV transmitted?
respiratory droplets
what does RSV cause in adults?
common cold
bronchitis
what does RSV cause in oldies?
pneumonia
what sx do infants get w/ RSV?
pronounced COUGH
expiratory WHEEZING
T/F: there is a rapid ag test for RSV
TRUE!
detects virus in respiratory secretions
what can you give to severely ill hospitalized infants if they have RSV?
ribavirin
other than meds, what’s another option to fight RSV?
passive immunization w/ ab
what are the surface spikes on RSV?
FUSION proteins (not HA & NA like in influenza)
what do the surface fusion proteins of RSV do?
cause cells to fuse, forming a multinucleate giant cell»_space;> syncytia (thus the name)
when does RSV cause outbreaks?
every winter
T/F: virtually everyone has been infected w/ RSV by 2-3 yo
TRUE
what group gets outbreaks of respiratory infections from RSV?
hospitalized infants
how can you control RSV outbreaks?
wash your hands
use gloves
what CXR finding is suggestive of RSV?
perifular fullness (perihilar?)
what are the 3 key things in a case presentation of RSV?
6-week-old infant
distress
wheezing
what do parainfluenza viruses (PIV) cause in children?
croup
laryngitis
bronchiolitis
pneumonia
what do parainfluenza viruses (PIV) cause in adults?
common cold
how are parainfluenza viruses (PIV) transmitted?
respiratory droplets
what is the main cause of croup in children under 5 yo?
PIV 1 & 2
what is croup characterized by?
barking cough
hoarseness
other than croup, what can PIV cause?
variety of respiratory diseases common cold pharyngitis laryngitis otitis media bronchitis pneumonia
where can you see PIV 3?
lower respiratory infections in children
how do you diagnose PIV?
clinically
T/F: parainfluenza virus is a paramyxovirus
TRUE (parapara)
what are the surface spikes of parainfluenza?
HA
NA
AND fusion (all 3!)
how are the parainfluenza spikes grouped?
HA & NA proteins are on the same spike
F protein is on a separate spike
parainfluenza viruses cause upper & lower respiratory tract disease without (blank)
viremia
what neutralizes PIV infectivity?
ab to either HA or F protein
is there a vax or RX for PIV?
nope
neither
what AP x-ray finding is suggestive of croup?
steeple sign > tracheal narrowing
what sx should be a dead giveaway for croup?
BARKING COUGH
