HA entry
Hemagglutinin helps the particle attach to airway sugars.
Inhaled particles reach airway cells. Replication is fast; fever and cough follow an innate alarm.
Each copy round adds mutants. Most fail. A few drift the surface enough to matter next winter.
Parts
NA exit
Neuraminidase helps new particles leave the cell surface.
Nucleus step
Unusual for an RNA virus, influenza replication uses the host nucleus.
Airway damage
Killed cells and inflammation make secondary bacterial pneumonia more likely in some people.
Antibody target
HA head changes fastest; stem is more conserved and a research aim for broader shots.
Animal mixers
Pigs and birds can host several A viruses; that ecology is watched, not recreated at home.
Life cycle
1Inhale
Droplets or aerosols reach a new airway.
2Replicate
Airway cells make huge numbers of particles for a few days.
3Shed and feel ill
Cough and contact move virus while fever and aches peak.
4Recover or complicate
Most people recover. A minority develop pneumonia or worsening of chronic disease.
No engineering steps are described.
Keep exploring
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Familiarity 68