The impact of altitude on hospitalization and hospital mortality from pandemic 2009 influenza A (H1N1) virus pneumonia in Mexico

OBJECTIVE: To determine the effect of altitude of residence on influenza A (H1N1). MATERIALS AND METHODS: We analyzed 207 135 officially notified of influenza-like illness (ILI) cases, 23 048 hospitalizations and 573 deaths during the first months of the novel pandemic influenza A H1N1 virus, to examine if residents of high altitude had more frequently these adverse outcomes. RESULTS: Adjusted rates for hospitalization and hospital mortality rates increased with altitude, probably due to hypoxemia.