Influenza Flashcards
Influenza Major Serotypes
A, B, C
Influenza Order
Mononegavirales
Family
Orthomyxoviridae
Genera
Influenzavirus
Structure
Spherical, pleomorphic
Characteristics
Enveloped, ssRNA negative-strand virus
Capsid
Helical
Capsid Assembly
Citoplasm
Segments are monocistronic except___ and ______
Non
structural (NS1, NS2), Matrix (M1, M2)
genes
Influenza A & B virus has ____ segments which is ____
8, complete
Influenza C has ____ segments
7
Unique Properties of Influenza (4 traits)
- High mutability
- Genetic diversity
- Genetic reassortment
- Antigenic change
Where does RNA transcription and translation take place?
Nucleus
What are envelope glycoprotein spikes?
- Hemagglutinin (HA)
- Neuraminidase (NA)
Function of HA (haemagglutinin)
Viral entry into target cell
Function of (NA) neuraminidase
Release of viral particles from target cells and help in dissemination of virion particles throughout respiratory tract
Function of PA (acidic polymerase protein)
Endonuclease activity and help in cap snatching mechanism
Function of PB1 (basic polymerase protein - 1)
Viral mRNA transcription by 5’ cap snatching mechanism
Function of PB2 (basic polymerase protein - 2)
Unprimed replication of viral mRNA
Function of PB1-F2
Apoptosis of Host Cell
Function of M1 (Matrix Protein)
Role of attachment of vNRP to cell membrane and provide stability
Function of M2 (ion-channel protein)
Help in releasing vRNP from endosome to cytoplasm
Function of NP (nucleoprotein particle)
Participate in the nuclear import and export of vRNP and viral replication
Function of NS1 (nonstructural protein - 1)
Suppress IFN-Beta and host protein production
Function of NS2 (nonstructural protein - 2)
Help in nuclear import of vRNP
Surface glycoproteins are _____ and serve _______
antigenic, Special functional importance to the virus
The high frequency of variations of these two result in new serologic types
Hemagglutinin and Neuraminidase
Function of Hemagglutinin
*Binding to host receptor
* Internalization of the virus
*Facilitation of membrane
fusion events
*Target of neutralizing
antibodies
__, __, and __ are most associated with human infection
H1, H2, H3
Function of Neuraminidase
*Hydrolyzes the mucus on respiratory epithelium
*Destroys unoccupied
hemagglutinin receptors
__ and __ are most associated with human infection
N1 and N2
Only type ____ has subtypes
A
How many HA subtypes are there and how many affect humans?
16 HA, 4 affect humans (H1-H3, H5)
How many NA subtypes are there and how many affect humans?
9 NA, 2 affect humans (N1, N2)
What type of flu is H1N1? (Seasonal, Pandemic, Zoonotic)
Seasonal, Pandemic, Zoonotic
What type of flu is A(H3N2)? (Seasonal, Pandemic, Zoonotic)
Seasonal, Zoonotic
What type of flu is Spanish flu? (Seasonal, Pandemic, Zoonotic)
Pandemic
What type of flu is Type B and C? (Seasonal, Pandemic, Zoonotic)
Seasonal
Lineage of Type B influenza
Victoria and Yamagata
What type of flu is H5N1 and H9N2? (Seasonal, Pandemic, Zoonotic)
Zoonotic
Major Reservoirs of Influenza
Birds, swine, horses, dogs, cats, domestic
poultry
Minor Changes - antigenic _____; Majora Changes - antigenic _____
drift, shift
What happens in antigenic drift?
- minor mutations in the
hemagglutinin antigen - makes prior immunity less effective
- Occurs among influenza A viruses
What happens in antigenic shift?
- major changes occur in surface antigens
that occurs by reassortment - virus strains appear more different
antigenically from previously seen strains;
makes prior immunity less effective
TRUE OR FALSE: Antigenic drift occurs in all influenza viruses
FALSE, only influenza A
Influenza transmission happens through ___
coughing and sneezing
Children can be infectious for ___ days
=> 10
Young children can shed virus for __ days before their illness onset
=<6
Severely immunocompromised persons can shed virus for _____
weeks or months
Adults infectious from the day ____
before symptoms begin until 5 days after illness onset
Theories for the emergence of pandemic viruses
*Genetic reassortment between human and
animal viruses
*Direct transfer of viruses between animals and humans
*Re-emergence of viruses from unrecognized or unsuspected reservoirs.
Also known as the avian strain
H5N1
“swine flu” and also known as influenza
____, emerged in Mexico
A/H1N1
__ and __ subtypes are known to cause the
highly pathogenic form of the disease
H5 and H7
Influenza A (H7N9) circulate among ____
birds
Transmission of Influenza A(H7N9)
respiratory droplets or contact
TRUE OR FALSE: Influenza A(H7N9) is considered to be low pathogenic
avian influenza
TRUE
In March 2013, there was an Influenza A(H7N9) in what country?
China
In the Philippines, what influenza strand affected a cumulative of 24 provinces?
H5N1
Strand H5N6 affected which province?
Guimba, Nueva Ecija
Strand H7N7 affected which province?
Mexico, Pampanga
Influenza causes the cellular ____ and _______ of superficial mucosa
destruction, desquamation
Influenza can lead to ____
Secondary bacterial superinfection
In influenza pathogenesis, there is a disruption of ____
mucociliary escalator
Local symptomatic phase
cellular damage, edema
Systemic symptomatic phase
cytokines, interferon
HA binding, endocytosis, M2 ion channel, HA2 fusion peptide are terms correlated in what part of pathogenesis?
Attachment, Penetration, and Uncoating
In transcription and translation, nucleocapsid ____ the _____
enters. nucleus
In transcription and translation, RNA polymerase transcribes ____ to _____
(-) ssRNA, (+) ssRNA
What happens in viral replication
- (+) ssRNA acts as a template to produce new (-) ssRNA.
- Nucleocapsid forms with viral RNA and NP proteins.
In maturation and release, _____ is exported to ______
nucleocapsid, cytoplasm
In maturation and release, __ and __ is inserted into host cell membrane
HA & NA
Incubation period length
2 days (range 1-4 days)
Symptoms of Influenza
Abrupt onset of fever, myalgia,
sore throat, nonproductive
cough, headache
Immunity depends on __________ and ___________
immunity to previous variant circulating in
population and on relatedness of the two variants
Most epidemics are due to antigenic (drift/shift)
shift
Antibody against H protein: protective; Ab against N protein: ____
Disease severity
Diagnostic Tests for influenza
- Viral culture
- Serology
- Rapid antigen testing
- polymerase chain reaction (PCR)
- Immunofluorescence
TRUE OR FALSE: Throat swab
specimens are typically more effective than nasopharyngeal specimens
False, opposite
Treatment
Neuraminidase inhibitors (NAIs) Oseltamivir and Zanamivir
Treatment is beneficial for:
- pregnant patients
- patients with progressing lower respiratory disease or pneumonia
- patients with underlying medical conditions