The influenza A H1N1 virus is both similar and different from previous influenza A viruses that have caused seasonal flu in recent years. The symptoms associated with the H1N1 virus are very similar to those of other influenza A viruses causing seasonal flu.
One difference between the 2009 H1N1 virus and seasonal influenza A viruses is the time of year in which the infection is at its peak. The influenza 2009 H1N1 virus was prevalent during warmer weather months in 2009, whereas the peak time for seasonal influenza viruses is winter months.
Another way in which the H1N1 virus differs from seasonal flu viruses is the age group that is most affected. The number of cases and severity of the disease has been greater in the younger population, whereas most seasonal influenza virus-related deaths have been reported in those age 65 and older.
