Clinical and epidemiological findings in patients with pandemic A (H1N1) 2009 influenza in uppsala county, Sweden

Background:Descriptive analyses of influenza A (H1N1) 2009 were conducted on the pandemic (H1N1) 2009 influenza cases in Uppsala County. Uppsala County, situated close to the Stockholm urban area, has approximately 330 000 inhabitants. The pandemic influenza became a notifiable disease on May 2009 under the Swedish Communicable Disease Act, which implies that suspected influenza cases must be laboratory-verified and reported to the county medical officer and to the Swedish Institute for Infectious Disease Control.Methods:The analyses were performed using the patients' unique identification code via an electronic database system (eCRF) complemented by the patients' records.Results:In all, 456 confirmed influenza cases were reported from June 2009 to the end of December 2009. The main outbreak was restricted to 5 weeks in the autumn of 2009 when 82% of the cases were reported. Thirty-five percent of the patients had underlying medical risk conditions. No difference in symptoms was found between patients with underlying medical conditions and patients without risk. However, 64% of the patients with underlying medical conditions received antiviral therapy compared with 24% for the other patients. Patients with medical conditions received the vaccination in the beginning of the epidemic, whereas patients without risk received the vaccination at a later time. Forty-nine patients admitted vaccination, and of these, 46 received the vaccination 1week or less before onset of illness. The study showed that the epidemiological and clinical picture did not differ from seasonal influenza and that younger age groups were more affected than older age groups (i.e., older persons had some protection, probably through earlier contact with similar virus strains).Conclusions:The pandemic-based information from national and international authorities was crafted in the shadow of the threat from H5N1 avian influenza and was not in proportion to mainly mild-to-moderate illness caused by the 2009 H1N1 pandemic.