Swine flu kills more than 10% of those admitted to hospital with the virus, research by a US Government body has suggested.
A study by the Department of Public Health in California claimed that around 20% of older patients ill enough to be admitted to hospital with H1N1 were eventually killed by the condition, with a further third requiring intensive care and deaths occurring in all age groups.
The findings, published in the Journal of the American Medical Association, suggest that swine flu is potentially more dangerous than many people believe.
Investigating 1,088 cases between April 23 and August 11 this year, the study recorded 118 deaths among the test group - a mortality rate of 11%.
Fatalities were found to be most common in people aged 50 and over, for whom death rates rose to almost 20%, with viral pneumonia and acute respiratory distress syndrome being the biggest killers.
Seven per cent of deaths were among children younger than 18.
The authors say that many of those who died did so just 12 days after the onset of symptoms.
Suggesting measures to curb the risk posed by the virus, the report said: ‘Clinicians should maintain a high level of suspicion for pandemic 2009 influenza A (H1N1) infection in patients presenting currently with influenza-like illness who are older than 50 years or have known risk factors for influenza complications, regardless of rapid test results.
“Hospitalised infected cases should be carefully monitored and treated promptly with antiviral agents.”