MMSC 415 Part 2: Primary (Oxthomyoxoviridaoe Influenza)

Orthomyxoviridae

Family of enveloped, segmented single-stranded RNA (ssRNA) viruses that includes influenza viruses.

Hemagglutinin (H / HA)

Influenza surface protein that binds to host sialic acid residues to allow viral entry.

Neuraminidase (N / NA)

Influenza surface enzyme that cleaves newly formed budding viruses from infected host cells.

Influenza A

Most severe influenza type that infects both humans and animals and undergoes antigenic shift and drift.

Influenza B

• Influenza type that only infects humans and consists of two lineages: B/Victoria and B/Yamagata.

Influenza C

Influenza type with only 7 RNA segments that lacks a neuraminidase gene and causes mild upper respiratory illness.

Antigenic Drift

Gradual, continuous minor structural changes in H and N antigens caused by point mutations during RNA replication, leading to annual seasonal outbreaks.

Antigenic Shift

Abrupt, major antigenic change resulting in novel H or N antigens via genetic reassortment when two strains co-infect the same cell (e.g., in pigs), causing pandemics.

Oseltamivir (Tamiflu) / Zanamivir (Relenza) / Peramivir (Rapivab)

Neuraminidase inhibitor antiviral drugs used to treat influenza.

Baloxavir (Xofluza)

Endonuclease inhibitor antiviral drug that blocks viral RNA transcription.