Impact of the Novel Influenza A (H1N1) during the 2009 Autumn-Winter Season in a Large Hospital Setting in Santiago, Chile

• Published in: Clinical infectious diseases Vol. 50; no. 6; pp. 860 - 868
• Main Authors: Torres, Juan Pablo, O'Ryan, Miguel, Herve, Beatrice, Espinoza, Ricardo, Acuña, Guillermo, Mañalich, Jaime, Chomalí, May
• Format: Journal Article
• Language: English
• Published: Oxford The University of Chicago Press 15.03.2010; University of Chicago Press; Oxford University Press
• Subjects: Adolescent; Adult; Age; Age distribution; Antigens, Viral - analysis; Antiviral Agents - therapeutic use; ARTICLES AND COMMENTARIES; Biological and medical sciences; Child; Child, Preschool; Childrens health; Chile - epidemiology; Demographics; Emergency medical care; Emergency Service, Hospital; Epidemics; Female; H1N1 subtype influenza A virus; Hospitals; Humans; Infant; Infectious diseases; Influenza A virus; Influenza A Virus, H1N1 Subtype - isolation & purification; Influenza, Human - epidemiology; Influenza, Human - pathology; Influenza, Human - therapy; Influenza, Human - virology; Intensive care units; Male; Medical sciences; Middle Aged; Nasopharynx - virology; Patients; Pneumonia; Polymerase chain reaction; Reverse Transcriptase Polymerase Chain Reaction; School age children; Swine flu; Symptoms; Vaccines; Viruses; Young Adult; South America; Chile; America; Santiago Chile; Infection; Hospital; Winter; Influenza A (H1N1)
• ISSN: 1058-4838; 1537-6591
• DOI: 10.1086/650750

Background. In Chile, the novel influenza A (H1N1) epidemic began in the middle-high income area of Santiago. Clinical and laboratory surveillance was intensified with the aim to characterize the epidemic and determine its impact in a large hospital setting. Methods. Demographic and clinical data were obtained from all patients whose symptoms met the clinical definition of influenza A (H1N1) infection during the epidemic period. Laboratory confirmation was obtained by use of a nasopharyngeal antigen detection test for influenza A and/or influenza A (H1N1) polymerase chain reaction (PCR). A case was considered confirmed if the antigen detection test result for influenza A and/or the PCR test result were positive. Results. The total number of emergency department (ED) visits increased by 88.5% from a mean of 14,489 ED visits in 2006–2008 to a mean of 27,308 ED visits in 2009, during the epidemic period. There were 10,048 patients who were clinically diagnosed with influenza A (H1N1), and they represented 78% of all visits, of which 4591 (45.6%) were laboratory confirmed. The median time from symptom onset to diagnosis was 1 day, and 99.7% of individuals received antiviral treatment. School-aged children represented 67% of ED visits at the beginning of the epidemic and 24% of ED visits at the end of the epidemic. Only 2% of cases were hospitalized; of these, 70% of cases occurred in patients 6–50 years of age, and 32% of cases occurred in patients who had an underlying medical condition. Eleven patients (age range, 1–53 years) required admission to the intensive care unit (ICU); 6 of these patients had pneumonia with or without hemodynamic shock. No influenza-associated deaths occurred. Conclusions. Many cases of influenza A (H1N1) occurred in school-aged and adult individuals who required an ED visit; these visits resulted in a low impact on the use of hospital beds. Aggressive ICU management and/or experience in extracorporeal membrane oxygenation significantly improved outcomes. Early antiviral treatment may have played an important role in the low number of severe cases. Vaccines targeted for school-aged children and young adults may modify the first epidemic wave in the northern hemisphere.