[1]China Japan Friendship Hosp, Ctr Resp Med, Dept Pulm & Crit Care Med, Beijing 100029, Peoples R China.
[2]Natl Clin Res Ctr Resp Dis, Beijing, Peoples R China.
[3]Chinese Acad Med Sci & Peking Union Med Coll, Beijing, Peoples R China.
[4]Chinese Acad Med Sci, Inst Resp Med, Beijing, Peoples R China.
[5]Capital Med Univ, Dept Resp Med, Beijing, Peoples R China.
[6]Univ Oxford, Ctr Trop Med & Global Hlth, Oxford, England.
[7]Univ Virginia, Sch Med, Dept Med, Charlottesville, VA 22908 USA.
[8]Chinese Ctr Dis Control & Prevent China CDC, Natl Inst Viral Dis Control & Prevent, Beijing, Peoples R China.