[1] Univ London Imperial Coll Sci Technol & Med, Infect Dis Sect, London, England
[2] Univ Cambridge, Dept Vet Med, Cambridge, England
[3] Univ Massachusetts, Sch Med, Program Gene Funct & Express, Program Mol Med, Worcester, MA USA
[4] Univ Geneva, Dept Microbiol & Mol Med, Geneva, Switzerland