Introduction: Respiratory infections increased in Mexico in 2009 due to an epidemic of influenza.
Methods: To compare symptoms and infectivity of influenza A(H1N1) and seasonal influenza we evaluated epidemiological data and microbiological sampling of health workers (HW) and patients who probably had influenza.
Results: From April to November 2009 we studied 83 HW (29 with influenza A(H1N1) and 8 with seasonal influenza) and 71 patients (26 and 11, respectively). The subtypes of influenza had similar clinical data.
Conclusions: Fifteen patients with immunosuppression or chronic diseases developed fatal pneumonia; the infectivity was greater for influenza A(H1N1).
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