Two studies in the Journal of the American Medical Association, neither particularly happy.
Data from a California study published today in the November 4 issue of the Journal of the American Medical Association have revealed that Swine Flu kills more than 1 in 10 of those it affects severely enough to put in a hospital. The study, conducted by the California Department of Public Health investigated H1N1 flu cases in California between April 23 and August 11, 2009, including fatality and other clinical features. The authors found that the overall fatality associated with H1N1 flu in California was 11 percent and was highest (18 percent – 20 percent) in persons aged 50 years or older.
The spring outbreak of 2009 influenza A(H1N1) infection in Canada affected primarily young, female, and aboriginal patients without major comorbidities, and conferred a 28-day mortality of 14.3% among critically ill patients. A history of lung disease or smoking, obesity, hypertension, and diabetes were the most common comorbidities. Critical illness occurred rapidly after hospital admission and was associated with severe oxygenation failure, a requirement for prolonged mechanical ventilation, and the frequent use of rescue therapies.
Why the difference?
I suspect that the data is a bit skewed in the latter study — it focused only on patients admitted to ICU. And the young and previously healthy, I think (as a observation), are more likely to be admitted as a rule to ICU with influenza then the old with multiple co-morbities.
What’s really shocking are the mortality rates if hospitalized: 11% in the California study (up to 20% if older than 50), and 14.3% in the Canadian study.