Influenza Mortality Rate
The mortality rate from seasonal influenza in the United States ranges from approximately 12,000 to 52,000 deaths annually, with case-fatality rates varying dramatically by age: 0.4-0.6 per 100,000 in persons aged 0-49 years, 7.5 per 100,000 in those aged 50-64 years, and 98.3 per 100,000 in adults over 65 years. 1
Seasonal Influenza Mortality: The Core Numbers
Adults over 65 years account for more than 90% of all influenza-related deaths, making age the single most critical mortality risk factor. 1 During typical influenza seasons from 1990-1999, approximately 36,000 influenza-associated pulmonary and circulatory deaths occurred per season in the United States, compared to 19,000 deaths during 1976-1990. 1
Age-Stratified Mortality Rates
The mortality burden is heavily concentrated in older adults:
- Ages 0-49 years: 0.4-0.6 deaths per 100,000 population 1
- Ages 50-64 years: 7.5 deaths per 100,000 population 1
- Ages ≥65 years: 30 to >150 deaths per 100,000 population during epidemic seasons 1
Epidemic Variability
From 1972-1995, more than 20,000 influenza-associated deaths occurred during each of 11 different U.S. epidemics, and more than 40,000 deaths occurred in 6 of these 11 epidemics. 1 The overall annual estimate is approximately 30,000 to 35,000 deaths per year in the United States. 2, 3
Pandemic Mortality: A Different Picture
Pandemic influenza demonstrates vastly different mortality patterns compared to seasonal influenza:
2009 H1N1 Pandemic (Low-Moderate Severity)
- Total deaths: Approximately 12,000 in the United States 1
- Case-fatality rate: <0.5% overall 2
- Age distribution: 87% of deaths occurred in persons ≤65 years (mean age 43 years), completely reversing the typical seasonal pattern 1
Historical Pandemics
- 1968 H3N2 pandemic: ~30,000 U.S. deaths, with approximately half in those ≥65 years 1
- 1957 H2N2 pandemic: ~70,000 U.S. deaths, with 64% in older adults despite highest infection rates in school-aged children 1
- 1918 H1N1 pandemic: ~500,000 U.S. deaths with case-fatality rate of 2-3%, and 99% of deaths in persons ≤65 years 1
Global Burden
Globally, influenza affects nearly 10% of the world's population annually, resulting in approximately 500,000 deaths each year. 4 This translates to more than 200,000 hospitalizations and over 30,000 deaths annually in the United States alone. 2, 3
Critical Mortality Risk Factors
Beyond age, specific populations face dramatically elevated mortality risk:
- Nursing home residents: Highest mortality rates, but vaccination prevents 80% of deaths even when vaccine effectiveness against illness is only 30-40% 5
- Chronic medical conditions: Persons with cardiopulmonary disease, metabolic disorders, or immunosuppression face substantially higher mortality 5
- Infants <6 months: Hospitalization rates of 1,040 per 100,000 population, comparable to elderly adults 1
Temporal Trends and Virus Type
Influenza A (H3N2) seasons are associated with significantly higher mortality than H1N1 or influenza B seasons. 1 H3N2 viruses predominated in 90% of seasons from 1990-1999 compared to 57% from 1976-1990, partially explaining the increase in deaths during the later period. 1
The number of influenza-associated deaths is increasing over time, driven primarily by the aging U.S. population rather than increased virulence. 1
Key Clinical Caveat
Death from influenza rarely results from direct respiratory failure alone—instead, mortality typically occurs through gradual multi-organ failure, exacerbation of underlying cardiopulmonary conditions, and secondary bacterial pneumonia (particularly methicillin-resistant Staphylococcus aureus). 6, 3 This explains why >90% of deaths are coded as "pneumonia and influenza" rather than influenza alone. 1