Lecutre 18 Flashcards
What are common sites of respiratory virus infection?
The middle ear and sinuses of the head
What size of bacteria that are deposited in upper and lower airways?
1-5 micrometer. Viruses in coughed secretions will be deposited in high concentrations in the upper airways but can also reach the lower airways.
To cause disease they must attach, enter cells and replicate.
What does influenza attach to?
Sialic acid
What does Respiratory Syncytial virus attach to?
Heparin-like glycosaminoglycan
What does Rhinoviruses attach to?
Intercellular adhesion molecule 1
How does Respiratory Virus pathogensis
Attach to and enter respiratory epithelial cells
Replicate inside cells
Death of infected cells
due to viral replication and release
and/or immune responses
Impaired function of respiratory tract
Death or recovery
What are the consequences of manifestations of respiratory tract virus infections?
Result from damage to epithelium:
* narrowed airways due to swollen tissues
* obstructed airways due to loss of cilia,
viscous mucous, shed cells
Result from inflammation:
* fever, achiness, malaise, anorexia
What are the consequences of manifestations of respiratory tract virus infections in young and old people?
Generally more severe:
in very young infants narrow airways before illness
and very old people damaged airways before illness
May include bacterial infection of affected tissues
Most frequently managed problems
in NZ general practice
URTI 5.5%
Acute bronchitis 5.4%
Otitis media 4.9%
Tonsillitis 3.9%
What bacteria are the Common causes of respiratory infections?
Streptococcus pneumonia
Haemophilus influenzae
Moraxella catarrhalis
Streptococcus pyogenes
What viruses are the Common causes of respiratory infections?
Rhinoviruses
Coronaviruses
RSV
Influenza virus
Which infections are almost always due to viruses?
Colds Bronchitis Pharyngitis Influenza most respiratory infections don’t need an antibiotic
Influenza A structure?
HA (1-16)
NA (1-9) = surface proteins
Segmented genome = 8 RNA molecules
Describe the drift in influenza viruses
gradual accumulation
of mutations in genes with minor changes in HA and NA
Describe the shift in influenza viruses
abrupt reassortment of
genes between two strains with major changes in HA
and NA
What happens during influenza infections and what would you do?
Illness lasting 5-6 days
3-4 days in bed, off work
Morbidity, and mortality, esp in young and elderly
Episodes of illness approx every 7 years
What symptoms do you see during influenza?
Abrupt onset
Fever, chills, headaches, myalgia, malaise
Dry cough, pharyngeal pain, nasal discharge
Recovery with immunity
How do you diagnose influenza diagnosis?
Clinical presentation
Virus isolation on cell cultures
Detection of influenza antigens
PCR of influenza RNA
Serology
When and what happens when antibodies work?
Antibodies to surface proteins:
appear at 10-14 days post infection
enhanced if previous infection with similar strain
persist lifelong
protect against recurrent infection with same strain
What injections would you give for influenza?
Modestly effective treatment
Oseltamivir = “Tamiflu”
Moderately effective vaccine
changed annually
to anticipate drift in circulating strains
What are Respiratory syncytial virus? Stats?
RNA virus similar to measles and mumps
viruses
In culture adjacent infected cells merge
forming syncytia
60% children infected in 1st year,
100% by 3rd year
How does respiratory syncytial virus work?
Causes disease of any part of airway from nose and
middle ear to lungs
What disease does RSV cause and what are the consequences?
Bronchiolitis is the most common severe illness
(also known as “croup”)
affects children aged <3 years
wheezing and breathlessness for a couple of days
no vaccine and no antiviral treatment
How do you treat bronchiolitis?
Chest X ray of an infant with “croup” due to RSV bronchiolitis .
The arrows show inflammation of the bronchioloes
some benefit from corticosteroid therapy
What are rhinoviruses derived from?
picoviruses - tiny
What are rhinoviruses?
Very small RNA viruses
99 serotypes
Replicates in cells at
33-350C (nose not lungs)
Nasal and maxillary sinus disease in adults with cold
How are Rhinoviruses transmitted, incubated, where, symptoms and recovery?
Transmitted by respiratory droplets and
contaminated surfaces
Incubation period 1-4 days
Infection of nose and sinuses
Nasal mucous, sneezing, cough, sore throat
Minor fever, muscle aches etc
Recovery in 1-2 weeks
What are the treatments for Rhinoviruses?
Recovery with long-lasting immunity to that
serotype.
Symptomatic treatment
No effective antiviral treatment
No effective vaccine
