Influenza

Hemagglutinin (H)

Viral protein enabling cell entry

Neuraminidase (N)

Protein helping virus exit host cells

Antigenic Drift

Small, frequent mutations → seasonal flu

Antigenic Shift

Sudden, major mutation → pandemics

1918 Flu (H1N1)

Killed 50–100 million; deadliest modern pandemic

Group 1 vs 2 Theory

Immune response based on childhood exposure

Cytokine Storm

Hyperimmune reaction causing lung fluid accumulation

Spanish Flu

Misnamed pandemic; Spain reported openly

Richard Shope

Proved flu was viral using swine studies

Chicken Embryos

Used to culture virus for vaccine development

St. Louis vs Philadelphia

Contrasting case study in public health effectiveness

Black Red Cross Nurses

Faced racism; contributed crucial care

Antibody Test

Identifies viral exposure; developed in HIV era

1977 H1N1

Reappearance of old strain; likely lab origin

Gain-of-Function

Risky research mutating viruses to predict evolution

Pandemic Memory

1918 flu largely forgotten; unlike AIDS or COVID

Vaccine Limits

Constant reformulation needed due to mutation

Incubation Period

1–5 days; allows undetected spread

Misdiagnosis

Flu long thought bacterial (Bacillus influenzae)

Colonial Mortality

Higher death rates in global south due to neglect