10 Questions
What is the primary mechanism by which the influenza virus acquires genetic variation?
Reassortment
Which of the following is a characteristic of antigenic drift?
Gradual accumulation of point mutations over time
What is the primary mode of transmission of the influenza virus?
Airborne transmission
Which of the following is a recommended method for preventing the spread of influenza?
All of the above
What is the term for the process by which the influenza virus undergoes a sudden and drastic change in its antigenic properties?
Antigenic shift
What is the main function of the hemagglutinin protein in the influenza virus?
To recognize and bind to host cells
What is the primary cause of influenza symptoms?
The immune response to the virus
Which of the following is a characteristic of the influenza virus genome?
It is a single-stranded RNA genome
What is the term for the exchange of genetic material between different influenza viruses?
Reassortment
What is the primary goal of hand hygiene practices in preventing the spread of influenza?
To reduce the transmission of the virus through direct contact
Study Notes
Influenza Virus Characteristics
- Helical and spherical in shape
- Genome: -ve sense ssRNA, segmented into 8 segments
- Envelope has Haemagglutinin (HA) and Neuraminidase (NA) glycoprotein spikes
- Infects through the respiratory route
Viral Surface Antigens
- HA (Haemagglutinin) spike: 18 types, most common are H1, 2, 3, 5 (human strains), coded by genome segment 4
- NA (Neuraminidase) spike: 11 types, most common are N1, 2 (human strains), coded by genome segment 6
- Both spikes on envelope (10 nm long) and undergo antigenic variations
Classification and Structure
- Family classification: contains 3 genera of influenza virus: A, B, C, based on antigenic differences in Nucleocapsid (NP) and Matrix proteins
- NP responsible for helical symmetry, while Matrix proteins (M1) responsible for spherical shape
- M2 protein (ion channel) facilitates uncoating of the virus
Genus Influenza A Subtypes
- Subdivided into subtypes based on antigenic variations of HA and NA surface glycoproteins (18H and 11N)
Genome
- Negative sense single-stranded RNA, segmented into 8 segments
Haemagglutinin (HA) Functions
- Viral attachment protein: binds to sialic acid receptors on respiratory epithelial cell surface
- Promotes fusion of the envelope to the cell membrane
- Hemagglutinates human, chicken, and guinea pig RBCs
- Elicits protective neutralizing antibody response
Neuraminidase (NA) Functions
- Destroys neuraminic acid of mucin covering sialic acid receptors on respiratory epithelial cell surface
- Cleaves sialic acid on glycoproteins, including cell receptor, to facilitate infection and release of virus from infected cells
- Target for antiviral drugs: zanamivir (Relenza) and oseltamivir (Tamiflu)
This quiz covers the characteristics of the influenza virus, including its genome, surface antigens, and mode of infection. It also discusses the different types of haemagglutinin and neuraminidase spikes on the viral envelope.
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