Abstract

Background
The purpose of this paper is to investigate for the epidemiologic and clinical characteristics of patients with diagnosed novel influenza A (H1N1) and to evaluate the usefulness of clinical diagnosis. Methods: Out of 696 patients who visited the community sentinel hospital for novel influenza from 27 Aug 2009 to 10 Sep 2009, 557 patients had performed the conventional RT-PCR test. Of these patients, 540 patients were enrolled to our study excluding 17 patients who had performed the test for their own request without clinical suspicion. Results: The 79 patients (14.6%) were finally diagnosed as novel influenza by conventional RT-PCR, with median age 19. Main clinical symptoms were febrile sense, cough, rhinorrhea, and sore throat. The odd ratios of the symptoms with fever, febrile sense and myalgia, acute febrile respiratory disease, influenza-likely illness, the age with 10 to 19, and students were statistically significantly higher in finally diagnosed patients group. The sensitivity, specificity, and positive and negative predictive values of rapid antigen test for influenza were 29.4%, 99.3%, 90.9%, and 85.7%, respectively. In the acute febrile respiratory disease and influenza-likely illness, the sensitivity, specificity, and positive and negative predictive value were 77.2%, 38.3%, 17.7%, and 90.7%, and 69.6%, 46.6%, 18.3%, and 89.9%, respectively. Conclusion: In the community sentinel hospital, the patients with novel influenza A (H1N1) present the clinical manifestations similar to the common seasonal influenza. Primary health care providers might have a lot of difficulties in differentiation and treatment necessitating consideration of a variety of diagnostic methods.

• Keywords: Influenza A Virus, H1N1 Subtype; RT-PCR; Rapid Antigen Test; Acute Febrile Respiratory Disease; Influenza-Likely Illness