[1] Univ Tennessee, Coll Med, Dept Med, Div Infect Dis, Memphis, TN USA
[2] Univ Tennessee, Coll Med, Dept Med, Div Pulm & Crit Care Med, Memphis, TN USA
[3] Univ Tennessee, Coll Med, Dept Otolaryngol & Maxillofacial Surg, Div Biostat & Epidemiol, Memphis, TN USA
[4] Univ Tennessee, Coll Med, Dept Prevent Med, Memphis, TN USA
[5] Reg Med Ctr, Hosp Epidemiol Unit, Memphis, TN USA
[6] Vet Affairs Med Ctr, Memphis, TN USA