Seropositivity for Influenza A(H1N1)pdm09 Virus among Frontline Health Care Personnel oleh Kumar Alagappan, Robert A. Silverman, Kathy Hancock, Mary Frances Ward, Meredith Akerman, Fatimah S. Dawood, Alicia Branch, Sandra De Cicco, Evelene Steward-Clark, Megan McCullough, Karen Tenner, Jacqueline M. Katz