Influenza Viruses

• influenza viruses are (–)ssRNA organisms

• influenza viruses type A, B and C

• influenza genome is very diverse

Structure of influenza

• The structure of influenza virus consists of a lipid envelope surrounding the viral genome and proteins

• The viral envelope contains two major glycoproteins: hemagglutinin (HA) and neuraminidase (NA)

Designation of strains of influenza

• Strains are designated based on their HA and NA types; for example, H1N1 or H3N2.

Genomic diversity of influenza

• Genome of flu viruses: 14,000 nucleotides of negative-sense single-stranded RNA

• Influenza virus genome segmented into eight fragments of RNA containing 11 genes - encodes approximately 14 proteins

• Structure significant for spread and severity of disease symptoms

Creation of new viral strains

• New flu strains form through antigenic shift where genetic material from different flu viruses combine to make it more deadly

Infection and replication:

• Steps:

1. Influenza virus binds to host cell receptors

2. The virus enters the cell

3. The virus releases its genetic material into the cell

4. The virus's genetic material is transcribed into viral proteins

5. The viral proteins are assembled into new virus particles

6. The new virus particles are released from the cell

Cellular pathology of influenza infection:

• Damage caused by direct effects such as cell lysis or indirect mechanisms like cytokine release contributing significantly towards symptoms severity including fever coughing sneezing body pains sore throat nasal congestion fatigue etc.