Viral Respiratory Tract Infections Flashcards
What are the types of respiratory tract infections?
- Upper
- Middle
- Lower
What are the upper respiratory tract infections?
- Rhinitis
- Pharyngitis
- Tonsillitis
- Otitis Media
- Sinusitis
What is rhinitis commonly caused by?
Rhinovirus
What are the symptoms of rhinitis?
Runny nose’ and sneezing
What is pharyngitis caused by?
Adenoviruses or coxsackie virus
What does pharyngitis result in?
Fever and painful infected throat producing pus or exudates
What happens in tonsillitis?
The tonsils become red and swollen, and exudates produced
What is a common cause of tonsillitis?
EBV
What is a potential complication of tonsillitis?
Quincy
When do otitis media and sinusitis usually occur?
When sinuses or the middle ear (Eustachian tube) become occluded from inflammation
What does otitis media and sinusitis produce?
Fever and pain
What is otitis media and sinusitis caused by?
- S. Pyogenes
- S. Pneumonia
- H. Influenzae
What are the middle respiratory tract infections?
- Laryngitis
- Tracheitis
- Laryngo-tracheo-bronchitis
What does laryngitis produce?
A hoarseness and loss of voice
What does tracheitis produce?
- Tracheal tiredness
- Retrosternal pain on breathing
What is laryngo-tracheo-bronchitis known as?
Croup
How common is croup?
Relatively
What are the symptoms of croup?
- Barking cough
- Hoarseness
- Stridor
What is stridor?
High-pitched wheezing
What causes stridor in croup?
Occlusion from inflammation, as cartilage rings make trachea non-expandable
What are the lower respiratory tract infections?
- Acute bronchitis
- Bronchiolitis
- Pneumonia
What is acute bronchitis?
Cough associated with whitish sputum
What change is seen on chest X-ray with acute bronchitis?
None
In whom does bronchiolitis mainly occur?
Infants
What are the symptoms of bronchiolitis?
- Wheeze
- Cough
- Dyspnoea
How long does bronchiolitis last?
Several days
What is the most common cause of bronchiolitis?
RSV
What can viruses act as triggers to?
Underlying chronic conditions
What underlying chronic conditions can viruses act as triggers to?
- Asthma
- Cystic Fibrosis
- COPD exacerbations
What adversaries for viral RTIs are there?
- Influenza types A, B, and C
- Adenoviruses
- Respiratory syncytical virus (RSV)
- Parainfluenza virus types 1, 2, and 3
- Rhinovirus
- Coxsackie virus
- Coronaviruses
How can influenza A be further classified?
Depending on the antigens on their surface
What happens to the antigens on the surface of influenza A?
Point mutations occur
What do point mutations in the antigens on the surface of influenza A produce?
Antigenic drift
What are adenoviruses?
DNA viruses
How many serotypes are there of adenoviruses?
More than 50
How many of the serotypes of adenoviruses cause disease?
9
What is RSV?
A paramyxovirus
How many major serotypes of RSV are there?
2
How do the major serotypes of RSV differ?
In their antigenic properties
Who does RSV infect?
Children in their first 3 years of life
What does RSV cause?
Bronchitis, bronchiolitis, and pneumonia in infants
Is there a vaccine to RSV?
No
What is parainfluenza virus the major cause of?
Croup in children
How does parainfluenza virus cause croup?
By infecting the tracheobronchial tree
Where can parainfluenza virus be found in adults?
In the upper respiratory tract
What does rhinovirus cause?
Rhinitis
How many serotypes of rhinovirus are there?
More than 100
What type of viruses are rhinoviruses?
Picornaviruses
What kind of viruses are coxsackie?
Echoviruses
What do coronaviruses cause?
Coryza-like illness, similar to rhinitis
Can a virus be identified by the symptoms and syndromes caused?
No
Why can a virus not be identified simply by the symptoms and syndromes caused?
As there is so much overlap between viruses and conditions caused
What do acute viral respiratory illnesses cause?
High rates of illness in children
What is the result of acute viral respiratory illnesses caused high rates of illness in children?
They are a large proportion of GP consultations
In whom do acute viral respiratory illnesses cause a large proportion of deaths?
The elderly
What are influenza viruses made up of?
3 different subtypes, A, B, and C
What does type A influenza undergo?
Genetic shift
What do the influenza viruses contain?
A lipid protein coat
What does the lipid protein coat of influenza viruses have?
Two main antigens expressed within it
What are the main antigens expressed within the lipid protein coat of influenza viruses?
- Haemagglutin
- Neuraminidase
What are haemagglutin and neuraminidase used to do?
Classify the virus into sub-classification
How does the virus use haemagglutin?
- To adhere to the host cell
- Facilitates the entry of the viral genome into the target cells
How does the virus use neuraminidase?
To facilitate its release from the host cell
What is the clinical significance of the influenza viruses use of neuraminidase?
It can be used to some effect against influenza viruses for antiviral therapy
Give two examples of influenza viral classifications based on haemagglutin and neuraminidase?
- H1N1
- H3N2
What part of influenza viruses undergo antigenic changes?
- Haemagglutin
- Neuraminidase
What is antigenic drift?
Point mutations that occur in the virus genome that allow slightly new variants of the haemagglutin and neuraminidase to be altered slighlty.
The introduction of a new influenza subtype into the population
What does antigenic drift allow haemagglutin and neuraminidase to do?
Evade the immune system
What is antigenic drift responsible for?
Seasonal changes in the influenza virus
What is the result in the seasonal change in the influenza virus?
Vaccination against it needs to be renewed annually
What is the purpose of the antigenic drift process?
It is a process of continual evolution such that antibodies intended for its predecessor are ineffective against it
Currently, what are the stable lineages of influenza?
- H1N1
- H2N2
- H3N2
How are new strains of influenza produced?
A new subtype evolves as a result of genetic reassortment between human and animal influenza viruses
What do genetic reassortments between human and animal influenza viruses occur as a result of?
Direct reassortment, or via an intermediate host
In what species has genetic rearrangement occurred with human viruses?
- Avian flu
- Swine flu
Evaluate the use of current vaccines for influenza?
They are a good means of prevention, yet constantly have to be altered each year for that specific antigenic drift sequence
What does the influenza vaccine contain?
Attenuated viruses or purified surface antigens
What purified surface antigens may the influenza virus contain?
- HA
- NA
Who is given the vaccine for influenza?
Those at most risk of complications if infected with the virus
Who is at most risk of complications if infected with influenza?
- Over 65
- Diabetes
- Heart failure
- Renal failure
What is the purpose of the influenza vaccine?
Prevent morbidity or mortality
What are the main influenza antivirals that can be used?
Neuraminidase inhibitors
Give an example of a neurominidase inhibitor?
Zanaminvir
How do neurominidase inhibitors work?
As NA is essential for the release of viruses from virally infected cells, inhibiting the NA prevents further infection of other uninfected cells
What are the main problems with NA inhibitors?
- The rapid development of resistance
- The cost of treatment
- Only beneficial if given within 48 hours of onset of symptoms
How is diagnosis of influenza viruses made?
By direct immunoflouresence and NAAT
