[1] McGill Univ, Meakins Christie Labs, Montreal, PQ H2X 2P2, Canada
[2] CHUM Res Ctr, Montreal, PQ, Canada
[3] Univ British Columbia, Pulm Res Lab, Vancouver, BC, Canada
[4] Harvard Univ, Sch Publ Hlth, Boston, MA USA
[5] Massachusetts Gen Hosp, Infect Dis Unit, Boston, MA 02114 USA
[6] Harvard Univ, Sch Med, Boston, MA USA