Influenza Flashcards
What is the Flu?
flu is an acute viral infection of the respiratory
tract (nose, mouth, throat, bronchial tubes and
lungs)
it is a highly infectious illness which spreads
rapidly in closed communities
Structure of Influenza
SsRNA
Two surface antigens:
Haemagglutinin
Neuraminidase
Replication of influenza viruses
SsRNA replicates to produce more ssRNA and mRNA which codes for the viral proteins.
SsRNA replicated and assembles with the proteins into a nucleocapsid
Transmission of influenza
Respiratory route
Small particle aerosols - remain in air
Large particles or droplets - contaminate surfaces and individuals directly
Barriers to influenza virus
Respiratory epithelial cells are covered in mucus.
Ciliates respiratory epithelial cells sweep mucus upwards to be swallowed.
Muco-ciliary escalator
Macrophages, Natural killer cells, antibodies
How does influenza enter the cell
Hemagglutinin protein on surface binds to receptor and is taken in by receptor mediated endocytosis
Symptoms of Influenza
Fever Headache Cough Nausea Fatigue
Groups more prone to serious infections
Young children Older people Underlying health conditions Pregnant women Obese people
How is it diagnosed
Symptoms and clinical assessment
Treatment of influenza
Antivirals
Neuraminidase inhibitors - oseltamivir
Prevention - vaccine
What is antigenic drift
minor changes (natural mutations) in the genes of flu viruses that occur gradually over time – cause seasonal epidemics
What is antigenic shift
major changes in the genes of flu viruses that occur suddenly when two or more different strains combine. This results in a new subtype – cause widespread epidemics/pandemics
Consequences of antigenic shift
Antigenic shift leads to a new subtype of influenza virus May not have been seen in circulation in population for many years
Immune systems of many individuals have no defence against this new subtype
How does flu actually kill people
Immune system overreacts
Secondary infections
