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Transmission of 2009 Pandemic Influenza A (H1N1) Virus among Healthcare Personnel—Southern California, 2009

Jenifer L. Jaeger MD MPH, Minal Patel MD, Nila Dharan MD, Kathy Hancock PhD, Elissa Meites MD, Christine Mattson PhD, Matt Gladden PhD, David Sugerman MD, Saumil Doshi MD, Dianna Blau DVM PhD, Kathleen Harriman PhD, Melissa Whaley MS, Hong Sun MD, Michele Ginsberg MD, Annie S. Kao PhD, Paula Kriner MPH, Stephen Lindstrom PhD, Seema Jain MD, Jacqueline Katz PhD, Lyn Finelli DrPH, Sonja J. Olsen PhD and Alexander J. Kallen MD MPH
Infection Control and Hospital Epidemiology
Vol. 32, No. 12 (December 2011), pp. 1149-1157
DOI: 10.1086/662709
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Page Count: 9
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Transmission of 2009 Pandemic Influenza A (H1N1) Virus among Healthcare Personnel—Southern California, 2009
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Objective. In April 2009, 2009 pandemic influenza A (H1N1) (hereafter, pH1N1) virus was identified in California, which caused widespread illness throughout the United States. We evaluated pH1N1 transmission among exposed healthcare personnel (HCP) and assessed the use and effectiveness of personal protective equipment (PPE) early in the outbreak.Design. Cohort study.Setting. Two hospitals and 1 outpatient clinic in Southern California during March 28–April 24, 2009.Participants. Sixty-three HCP exposed to 6 of the first 8 cases of laboratory-confirmed pH1N1 in the United States.Methods. Baseline and follow-up questionnaires were used to collect demographic, epidemiologic, and clinical data. Paired serum samples were obtained to test for pH1N1-specific antibodies by microneutralization and hemagglutination-inhibition assays. Serology results were compared with HCP work setting, role, and self-reported PPE use.Results. Possible healthcare-associated pH1N1 transmission was identified in 9 (14%) of 63 exposed HCP; 6 (67%) of 9 seropositive HCP had asymptomatic infection. The highest attack rates occurred among outpatient HCP (6/19 [32%]) and among allied health staff (eg, technicians; 8/33 [24%]). Use of mask or N95 respirator was associated with remaining seronegative (). Adherence to PPE recommendations for preventing transmission of influenza virus and other respiratory pathogens was inadequate, particularly in outpatient settings.Conclusions. pH1N1 transmission likely occurred in healthcare settings early in the pandemic associated with inadequate PPE use. Organizational support for a comprehensive approach to infectious hazards, including infection prevention training for inpatient- and outpatient-based HCP, is essential to improve HCP and patient safety.

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