Although young people are most likely to be affected by H1N1 influenza, the elderly have the greatest risk for death due to H1N1 infection, according to study published online November 12, 2009 in the journal Lancet.

In April 2009, the first cases of H1N1 were registered in Mexico. Using information gathered from the influenza surveillance system, Mexican researchers explored protective and risk factors for H1N1 infection, severe disease, and death. They found that people aged 10 to 30 years accounted for more than half of reported H1N1 cases. However, elderly adults aged 70 and older were more likely to have severe H1N1 influenza. Among this age group, there was a 10.3 percent risk for death due to H1N1 infection. People with chronic diseases, such as high blood pressure, diabetes, and obesity, were found to have an increased risk for death.

The researchers also report that people who were immunized with the seasonal flu vaccine had a 35 percent lower risk for H1N1 infection. Based on their findings, they conclude that, despite its spread to 168 countries around the world, this strain of H1N1 influenza has not reached the proportions of the 1918 flu pandemic. This might be due, in part, because of global communication. However, the researchers also caution that the H1N1 virus is still evolving, so the threat is not over.

Source:

The Lancet, published online 12 November 2009.