Study of pandemic A nH1N1 influenza (2009-2010). Guiding signs in primary care and comparison with hospitalized cases

Objectives: to analyze the prediction’s capacity of clinical symptoms to diagnose nH1N1 Influenza in outpatients who were chosen by Aragon’s Sentinel surveillance Network. To compare outpatients with hospitalized cases during influenza A virus pandemic (2009-2010).

Methods: retrospective study of a randomized group of patients with symptoms of influenza who had laboratory-confirmation by PCR-RT and of all patients admitted to the reference hospital of Aragon. Comparison of epidemiological and clinical characteristics in outpatients and between outpatients and hospital cases.

Results: there were no clinical differences between the laboratory-confirmed by PCR-RT cases and the other outpatients, so it was not possible to find defining symptoms of infection. Hospitalized patients were younger, with higher percentage of underlying disease and comorbidity.

Conclusions: the epidemic of influenza A behaved as a benign disease, symptoms were similar to seasonal influenza. The clinical finding of having influenza symptoms in a high incidence week (weeks 43-48) was moderately predictive of influenza A infection.