UK Swine Flu Deaths 2010: Analysis of Cases Without Underlying Conditions

Data from UK Health Security Agency (UKHSA, formerly HPA) as of 21 October 2010.

Key Figures

• Total Deaths with Influenza A(H1N1)pdm09 as Underlying Cause: 457
• Deaths with NO Underlying Medical Conditions: 38% (~174 deaths)
• Deaths WITH Underlying Conditions: 62% (~283 deaths)

Context and Interpretation

• Pandemic period: April 2009 – March 2010 (UK first wave spring 2009, second wave autumn 2009).
• "No underlying conditions" means no *known* pre-existing risk factors per clinical records; some may have had undiagnosed conditions.
• Comparison: Seasonal flu deaths predominantly in elderly with comorbidities; pandemic H1N1 disproportionately affected younger, apparently healthy people.
• Case Fatality Ratio (CFR) estimated ~0.02–0.03% (much lower than initial fears).

Underlying Conditions in Those Who Died

• Chronic respiratory disease (asthma, COPD)
• Chronic heart disease
• Chronic kidney/liver disease
• Neurological/neurodevelopmental conditions
• Immunosuppression (disease or treatment)
• Diabetes mellitus
• Morbid obesity (BMI ≥40)
• Pregnancy/postpartum

Current Relevance

H1N1pdm09 now circulates seasonally. Annual vaccination, especially for risk groups, remains key. UKHSA publishes weekly influenza surveillance reports: gov.uk/government/collections/seasonal-influenza-guidance-data-and-analysis.