Swine-origin influenza virus (SOIV) in Louisiana, 2009

Since the new flu strain--named A(H1N1) or Swine Origin Influenza Virus (SOIV) to differentiate it from the seasonal H1N1--first emerged in Mexico and the United States in April, it has spread to 74 countries around the globe. The objectives of this article are to describe the initial stages of the epidemic in Louisiana and to draw some epidemiologic lessons for the future, which could be particularly useful if the pandemic continues during the winter season 2009-2010. Between April 22, 2009 (date when the first specimen was collected) to May 31, 2009, a six week period, there were 133 cases of SOIV infection detected in Louisiana. Cases were diagnosed in late April in several regions of the state, showing that when the first cases had been identified in Mexico and California, the infection was already widespread in Louisiana. The most affected age group was between the ages of five and 25.