[Pandemic influenza one year after the first wave: what did we learn?]

During year 2009 our nation experimented the first influenza pandemic wave due to the novel influenza A (H1N1) 2009 virus that emerged in the Northern hemisphere at the end of April, 2009. Estimated attack rate was about 6 to 12% affecting mainly to schoolchildren who presented with a mild disease. Age groups with highest risk of hospitalization were elderly people and children under 5 years old. Elderly patients and patients with co-morbidities had the highest risk to die. We have learned that clinical diagnosis of influenza has a laboratory confirmation in about 80% of cases but its correlation is lower in kids under 5 years old, especially in infants when RSV co-circulates with influenza virus. Laboratory diagnostic methods like DFA and immuno-chromatography have about 80% of sensitivity but a significantly lower rate in elderly patients compared to PCR. The clinical impact of this new virus justifies the recommendation to vaccinate traditionally established risk groups and to prescribe antiviral treatment to patients that acquire severe influenza or have risk factors to progress to complications.