L27 Viral infections of respiratory tract Flashcards
(38 cards)
The influenza virus is from the ____________ family. They are pleomorphic, with size 80-120mm with surface spikes.
They are enveloped/non-enveloped.
Othromyxoviridae
- enveloped
For the Influenza virus, there is 8 segment virus and each segment corresponds to a gene.
___________ and __________ genes encode envelop glycoproteins, which induce immune response.
How many serotypes are there in each gene?
Haemagglutinin (HA) and Neuraminidase (NA)
18H and 11N subtypes
Other than genes that encode envelop glycoproteins, there are internal genes such as ______, NS, NP; PB1, PB2 and PA [RNA polymerase].
Matrix (M)
M1 (matrix protein), M2 (ion channel)
Name the most important influenza viruses and their reservoirs.
- Influenza A: human, birds, pigs
- Influenza B: mutate more slowly, affect almost exclusively human
(3. Influenza C: affect human, but usually with minor symptoms)
How do we express the nomenclature of an influenza virus?
Subtype/animal (if human, not specified)/ location / strain/year
e.g. A/Hong Kong/483/1997 (H5N1)
What is antigenic drift?
full definition
Accumulation of minor antigenic changes due to replication error of RNA polymerase, lacking proofreading ability
(HA/NA genes)
In which type(s) of influenza virus does antigenic drift occur?
What are the consequences?
Influenza A and B
- Epidemic
- usually types A H3N2, A H1N1, B
- severe disease in high-risk groups, mild in healthy adults
What is the antigenic shift?
full definition
Gene reassortment of segments of the genome between 2 different strains, forming a new subtype with a mixture of surface antigens
(major change)
In which type(s) of influenza virus does antigenic shift occur?
What host?
- Influenza A only
- Aquatic birds (avain) as a gene pool: prone to all subtypes
What are the consequences of antigenic shift? (2)
- Pandemic production of a novel subtype with no immunity in the population
- High mortality
What are the modes of transmission of the influenza virus? (2)
- Respiratory
- droplet (>5 microns)
- ?airborne (droplet nuclei <5 micrins) for new flu - Direct contact
- contact with respiration contaminated items (e.g. fomites)
Influenza virus can survive in the environment in up to 48h. Is it easily disinfected? Why? How?
Yes, because it is an enveloped virus.
- By alcohol, soap and water/ hibiscrub/ >56 degrees
What is the common presentation of influenza virus infection?
- give examples of symptoms.
UTRI
(c.f. LRTI in avian flu)
- abrupt onset of fever and chills, sore throat, dry cough, myalgia
Symptom-wise, how to differentiate Influenza and Common cold? (2)
Influenza
- Fever
- Dry cough
Common cold
- Rhinorrhea
- Nasal congestion
Which of the following about influenza is correct?
A. There is a higher viral load in younger children than adults
B. There is a longer duration of symptom presentation in younger children
C. Younger children may present with bronchiolitis, croup and vomiting.
D. Otitis media in adults
E. Sputum production in adults
D is incorrect; should be in children
What are the 2 main approaches to diagnose influenza?
- Specimen
- Nasopharyngeal aspirate (NPA) - Detection method
- antigen detection: immunofluorescence, immunochromatography (rapid POCT)
- RT-PCR (reverse transcription) as a standard test
- cell culture rarely used
Best location of obtaining a specimen
A. Oral, oropharynx
B. Nasopharynx
C. Nasal
Sequence from better location to least good.
Nasopharynx > Nasal > oral, oropharynx
Which of the below has a higher viral yield?
A. Throat/nasal swab
B. Aspirate
B
What are the precautions when taking a nasopharyngeal aspirate?
- Require negative pressure
- Wear PPE
because it is an aerosol-generating procedure
Name the 2 main classes of antiviral treatment for Influenza. (2)
Briefly describe their MOA.
- M2 channel blockers (e.g. amantadine)
- inhibit uncoating
- not used nowadays due to resistance, ineffective for influenza B - Neuraminidase inhibitors
- Neuraminidase (NA) cleaves terminal sialic acid residues on the host cell surface to release progeny viruses
- Analogues of sialic acid to block the active site of NA
> uncleaved sialic acid residues bind to HA
> viral aggregation at the host cell surface
> reduce virion release through secretion
+/- promote production of pro-inflammatory cytokines
Name 2 neuraminidase inhibitors and state their respective route of intake and frequency.
Possible side effects?
- Zanamivir (Relenza) - Inhaltion BD - bronchospasm
- Oseltamivir (Tamiflu) - Oral BD - GI symptoms
(dosage adjustment required for Tamiflu, QD if Cr 10-30ml/min)
Baloxavir is a new anti-flu agent.
It is a cap-dependent endonuclease inhibitor
A. it interferes with viral RNA transcription
B. it blocks viral replication
C. single lV dose is needed
D. better for >12 years old
E. No dose adjustment needed for CrCl >50 min/min
F. May cause GI upset or headache
Only C is wrong
Singal Oral dose
What are the 2 main types of vaccination available for influenza?
- Inactivated vaccines (killed vaccine) [majority]
2. Live attenuated influenza vaccine (LAIV, FluMist) [one only]
Content of inactivated vaccine for influenza?
- Trivalent (2 stains of Influenza A + 1 strain of B)
2. Quadrivalent (2 stains of Influenza A + 2 strains of B
