Session 10- Influenza and Virology Flashcards
What is flu
An acute viral infection of the respiratory tract
Structure of the influenza virus
Orthomyxovirus are spherical, enveloped virus containing a segmented, negative strand RNA genome
2 surface antigens
- haemagglutinin (H) - 18 types binds to cell of infected person
- Neuraminidase (N) - 11 types - releases the virus from the host cell surface
Influenza A
Affects many animals undergoes antigenic drift and is responsible for pandemics
Influenza B
Only affects humans and undergoes antigenic drift- mainly affects older adults
Influenza c
Affects humans and pigs and undergoes antigenic drift and produces mild disease
How are influenza viruses transmitted
Person to person via the respiratory route- coughing, sneezing, inhaling
What are the first lines of defence in the innate immun system
1) respiratory epithelial cells are covered by a thick glycocalyx and tracheobronchial mucus that can trap viruses
2) ciliated respiratory epithelial cells continually sweep mucus up from the lower respiratory tract into the upper respiratory tract where it is swallowed
3) immunologic defences include secretatory IgA, natural killer cells and macrophages
How do viruses enter cells
They attach to sialic acid residues on host cell glycoproteins or glycolipids then entry via receptor-mediated endocytosis
What is attachment and fusion function associated with
Haemagglutinin protein
What is the viral release facilitated by
Neuraminidase protein which cleaves the sialic acid residue of the glycoprotein on the cell surface allowing release
Symptoms of i influenza
Fever Headache \ Sore throat Cough Aches Pains
Incubation time for influenza
5 days
Treatment of influenza
Antivirals
Neuraminidase inhibitors
Vaccination of vulnerable groups
What is genetic drift
Genome of the virus is constantly changing in small ways- point mutations- and this leads to genetic variation in both the surface antigens H and N
not as bad
What is antigenic shift
Major changes in the genes of flu viruses that occur suddenly when two or more different strains combine which results in a new subtype and is the
cause of widespread epidemics/pandemics
This refers to major changes in H and N proteins
VERY BAD