H1N1 Swine Flu of 2009 was Most Deadly for Younger Adults

The recently-discovered new strain of H7N9 bird flu continues to be a serious threat, and people continue to take precautionary measures, as it may be the next pandemic strain of influenza virus. Focusing on the previous H1N1 swine flu pandemic, a new study reveals that the swine flu of 2009 was the deadliest for people under the age of 65. Those above the age of 65 had a greater immunity due to previous exposure to similar viruses.

"Deaths from flu pandemics tend to skew younger than those from seasonal flu because of "antigenic recycling," or the fact that some parts of flu viruses have already made the rounds. Between 1918 and 1957, all flu viruses in circulation fell into the H1N1 category, so in 2009, older adults had some protection stemming from their prior experience with viruses of this type," Andrew Noymer, UC Irvine associate professor of public health and the study's co-author, said in a press statement.

He says that the swine flu pandemic was mild in the extent to which flu-related deaths took place. The most number of deaths was among the age group of 25-64.

Pneumonia and influenza deaths mostly occur in older people belonging to the age group of 65, but with the outbreak of H1N1 that soon became the prevailing flu strain in 2009, researchers noticed that death due to pneumonia and flu occurred in the age group that usually has low mortality rates. In the year 2009, nearly 53,692 deaths occurred due to pneumonia and influenza.  In 2010, the number dropped to 50,000. The mortality data was taken from the National Centre for Health Statistics.

Apart from the fatalities, the reason why the 2009 pandemic was considered unusual was because of its timing and age distribution of the deaths.

According to Noymer, the year 2009 stands as an excellent example of a virus strain with lenient mortality. Health officials should target pandemic vaccination campaigns to adults under the age of 65.