DOI:10.1111/irv.12123 www.influenzajournal.com
Original Article
Severe acute respiratory infections caused by 2009 pandemic influenza A (H1N1) among American Indians— southwestern United States, May 1–July 21, 2009 Anil Suryaprasad,a,b John T. Redd,b Kathy Hancock,c Alicia Branch,c Evelene Steward-Clark,c Jacqueline M. Katz,c For the Influenza Serology Working Groupc,* Alicia M. Fry,c James E. Cheek,b For the American Indian and Alaska Native Pandemic Influenza A (H1N1) Investigation Teama,b,c,d,e,f,g,h,i,j,k,l,* a
Epidemic Intelligence Service, Scientific Education and Professional Development Program Office, Centers for Disease Control and Prevention, Atlanta, GA, USA. bDivision of Epidemiology and Disease Prevention, Indian Health Service, Albuquerque, NM, USA. cInfluenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA. dDivision of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA. eImmunization Services Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA. fArizona Department of Health Services, Phoenix, AZ, USA. gTuba City Regional Healthcare Corporation, Tuba City, AZ, USA. hWinslow Indian Health Care Center, Winslow, AZ, USA. iWhiteriver Indian Health Service Hospital, Whiteriver, AZ, USA. jSells Indian Health Service Hospital, Sells, AZ, USA. k Phoenix Indian Medical Center, Phoenix, AZ, USA. lFlagstaff Medical Center, Flagstaff, AZ, USA. Correspondence: Anil Suryaprasad, Epidemic Intelligence Service Officer, 1600 Clifton Road NE, MS G-37, Atlanta, GA 30333, USA. E-mail:
[email protected] *See Appendix 1 for authors in the Influenza Serology Working Group and the American Indian and Alaska Native Pandemic Influenza A (H1N1) Investigation Team. Accepted 18 April 2013. Published Online 30 May 2013.
Background During April–July 2009, U.S. hospitalization rates for 2009 pandemic influenza A (H1N1) virus (H1N1pdm09) infection were estimated at 45/100 000 persons. We describe rates and risk factors for H1N1pdm09 infection among American Indians (AIs) in four isolated southwestern U.S. communities served by the Indian Health Service (IHS).
We reviewed clinical and demographic information from medical records of AIs hospitalized during May 1–July 21, 2009 with severe acute respiratory infection (SARI). Hospitalization rates were determined using denominator data provided by IHS. H1N1pdm09 infection was confirmed with polymerase chain reaction, rapid tests, or convalescent serology. Risk factors for more severe (SARI) versus milder [influenza-like illness (ILI)] illness were determined by comparing confirmed SARI patients with outpatients with ILI.
Methods
Among 168 SARI-hospitalized patients, 52% confirmed H1N1pdm09 infection and 93% had >1 high-risk
Results
had
condition for influenza complications. The H1N1pdm09 SARI hospitalization rate was 131/100 000 persons [95% confidence interval (CI), 102–160] and was highest among ages 0–4 years (353/ 100 000; 95% CI, 215–492). Among children, asthma (adjusted odds ratio [aOR] 32; 95% CI, 12–84) and age
