作者单位:St Jude Childrens Res Hosp, Dept Infect Dis, Memphis, TN 38105 USA[1]Univ N Carolina, Dept Biostat, Chapel Hill, NC USA[2]Univ N Carolina, Dept Microbiol & Immunol, Chapel Hill, NC USA[3]Univ N Carolina, Dept Family Med, Chapel Hill, NC 27514 USA[4]Univ N Carolina, Dept Pediat, Chapel Hill, NC USA[5]Univ N Carolina, Gillings Sch Global Publ Hlth, Dept Nutr, Chapel Hill, NC 27515 USA[6]