Viral infections of the resp system Flashcards
List the viruses associated with resp system conditions (6)
Rhino virus,
Enteroviruses,
Parainfluenza virus,
Respiratory Syncytial Virus, Human Metapneumovirus, Adenoviruses
list the common respiratory conditions (11)
Rhinitis, sinusitis, otitis media, tonsilitis, pharyngitis, tracheitis, bronchitis, bronchiolitis, laryngo-tracheo-bronchitis (croup), bronchopneumonia, pneumonia
Common old is limited to the LRT (t/f)
False. it is limited to the URT
Incubation period of the common cold
1 to 3 days
List the prodromal (early) symptoms of the common cold
headache, sore throat, fullness in the nose.
describe the mucus changes in the common cold as the condition progresses.
Profuse watery discharge from the nose (rhinorrhea) becomes thicker, muco-purulent and decreases
in volume
How long does a common cold take to resolve
About a week
List the viruses responsible for the common cold
Rhinoviruses: approximately 100 serotypes account for approximately 50% of colds
* Coronaviruses: NOT the serious coronaviruses
* Other enteroviruses
* RSV/Para-influenza/Influenza
Pharyngitis/tonsilitis is mostly caused by what microorganism species? which one is the most common culprit?
70% mostly viral
Mostly by adenovirus
In pharyngitis/tonsilitis, some viruses can cause _______________ which can progress to form ___________________
vesicles(blisters»»»> ulcers
Why is it called laryngotracheobronchitis in children?
In children difficult to distinguish due to very close anatomy, so sometimes called laryngotracheobronchitis
Laryngitis causes_______________________
Tracheitis causes______________
- Hoarse voice
- Sore throat and cough
Laryngotracheobronchitis can present as croup with stridor in children. What is that?
a particular high pitched sound with inspiration and sometimes
even on expiration – due to narrowed airway
T/F acute bronchitis is mostly caused by viruses
T
describe chronic bronchitis
not infective
* Due to irritation typically from smoking, but also from pollution, fumes, inhaled dust
What causes acute exacerbations of chronic bronchitis and how are they treated?
Acute exacerbations may be precipitated by infections though probably mostly these are viral. In practice often treated with antibiotics, but it is an area of uncertainty
what accounts for accounts for 30 -50% of community acquired pneumonia?
viral pneumonia
In pneumonia, how does the virus reach the lungs?
Mainly reach lungs via respiratory tract,
* Attach to respiratory epithelium by surface molecules that adhere to ‘receptors’
Healthy people are not at risk of viral pneumonia. T/F? Explain
Healthy people also susceptible
* But severity varies according to age and immune status, including prior exposure to virus
Possible complications of viral pneumonia
Can predispose to secondary bacterial infection, e.g. influenza can be followed by pneumococcal or
staphylococcal infection
* Permanent lung damage, e.g. bronchiectasis after certain destructive viral infections
What determines the site of infection for a particular virus?
Some viruses may have predilection or preference for certain sites
Sometimes depends on age and anatomy
Immune status ( age, previous infections or vaccinations, presence of immunodeficiency)
Why does the rhinovirus tend to infect the nose?
they prefer slightly cooler temperatures for replication
infants and young children more prone to clinical features of croup. Why?
because of narrow subglottic airway so swelling more easily leads to obstruction
Why are children more likely to develop otitis media?
Eustachian tube between nasopharynx and middle ear is more open in this age group so
also more likely to develop otitis media
Which bacteria causes tonsilitis/pharyngitis
streptococcus pyogenes
Which bacteria most commonly causes pneumonia?
streptococcus pneumonia
where does respiratory syncytial virus get its name?
Gets its name from the fact that it causes large syncytia in
cell culture
Define syncytia
: a multinucleate mass of
cytoplasm resulting from fusion of cells.
How does RSV attack? what does it use?
Contains F (fusion) protein used for infection and fusion of
virus membrane with cells
When are RSV infections most common?
Causes seasonal outbreaks every year in autumn/early
winter in community and in hospitals
At what age do children commonly get affected by RSV?
during their first year of life
What conditions does RSV commonly cause?
Causes bronchiolitis and pneumonia especially in infants
Why are infants more susceptible to RSV
Naturally acquired maternal antibodies don’t protect against RSV so infants exposed in the first 6 months of life can develop life threatening disease especially in premature or very small babies
Re-infections with RSV are more severe later in life. T/F
F. Re-infections are common throughout life, but become less severe, more like a common cold
long term consequences of RSV
wheezing
What made it possible for increased detection in respiratory infections in older adults
Use of multiplex PCR
How long does RSV infection take to shed off?
Virus can be shed for up to 3 weeks after infection normally
Which type of immunity is needed to clear the infection?
Cell mediated immunity
How are high risk infants protected against RSV?
Passive immunisation/Antibody prophylaxis in very high-risk infants during RSV season
IV infusion of monoclonal antibodies against F protein
* Prevents severe infection
Distinguish between RSV and human metapneumovirus
Only relatively recently discovered
Equivalent, though less severe than RSV
Occurs mainly in spring as opposed to autumn for RSV
describe the structure of parainfluenza virus
single stranded, enveloped RNA viruses
how many types of parainfluenza affect humans?
Wich one is most severe? which one is least severe?
4 antigenically distinct para-influenza viruses that infect humans
Parainfluenza virus that is more severe is 3. Less severe is 4
T/F
parainfluenza virus occurs seasonally and affects only children
F
throughout the year
Affects everyone
which virus causes croup?
Parainfluenza virus
Adenovirus structure
Unenveloped ds DNA viruses
Adenovirus occurs throughout the year. T/F
T
Symptoms of adenovirus
Cause a variety of syndromes involving the mucous membranes of the eye, respiratory and gastro
intestinal tract
* E.g. pharyngitis, conjunctivitis (‘pink-eye’), pneumonia, gastro-enteritis
Can cause ________________ in children especially if malnourished and can cause persistent lung disease
severe pneumonia
Structure of enteroviruses
ss RNA virus
Why is it called enterovirus?
As name suggests enteroviruses are shed in the faeces and transmitted via faecal oral route,
though they don’t cause gastro-enteritis
What virus causes Hand, foot and mouth disease- an upper respiratory tract
infection associated with rash on hands and feet and ulcers in the mouth
Coxsackie virus
Symptoms of rhinovirus infection
nasal discharge, nasal obstruction, cough, and/or a sore or scratchy throat lasting 5- 7 days,
gradually improving
Pathogenesis of rhinovirus
Virus adheres to receptor on nasal mucosa cells
* doesn’t damage cells but causes local production of various cytokines and kinins that cause
symptoms
symptoms of infection resolve before virus has cleared. T/F
T
What medical condition does rhinovirus commonly exarcebate?
asthma
Laboratory diagnosis of viral infections
Culture of virus
* Detection of viral antigens in clinical sample by microscopy
* Serology: demonstrating antibody response to infection in serum
* Detection of viral nucleic acids
Why is viral culture ineffective?
Viruses only replicate in living cells (Don’t grow on laboratory media)
* Traditional diagnosis in cell culture systems- slow (days to weeks) labour intensive
Why is detection of viral antigens impractical?
lectron microscopy (viruses not visible on light microscopy), useful for defining morphology in detail,
but not for routine diagnosis
why is flourescence microscopy impractical
Immunofluorescence microscopy: using fluorescent labelled antibodies to visualise viral antigens, also
tricky to do
Why is serology impractical
Looking for antibody response to infection – too slow
How has the shift to molecular diagnosis helped
Detection of viral nucleic acids from clinical samples
* By PCR or similar method to amplify (increase) viral genomic material
* Can detect DNA/RNA
* Extremely sensitive – can pick up very small amounts of virus
