Swine Flu vs. Spanish Flu: Key Differences Explained

Feature	2009 Swine Flu (H1N1pdm09)	1918 Spanish Flu (H1N1)
Virus Origin	Reassortant: swine, human, avian genes	Avian-like H1N1; direct zoonosis?
Pandemic Period	2009–2010 (1 major wave)	1918–1920 (3 waves: spring, lethal fall, winter)
Global Deaths	~150,000–575,000 (CDC est.)	50–100 million
Case Fatality Rate	<0.1%	2–3% (up to >10% in some groups)
Age Most Affected	Children, young adults, pregnant women	Young adults 20–40 (W-shaped curve)
Medical Countermeasures	Antivirals (oseltamivir), vaccine (months later), ICU support	None (no antivirals, no vaccine, limited supportive care)
Societal Impact	School closures, travel screening, moderate disruption	Mass mortality, economic collapse, wartime censorship

Both were H1N1 but differed vastly in virulence, population immunity, and medical context.