[1] Univ Southampton, Fac Med, Acad Unit Clin & Expt Sci, Southampton SO9 5NH, Hants, England
[2] Hlth Protect Agcy, Publ Hlth Lab, Southampton, Hants, England
[3] Univ Hosp Southampton NHS Fdn Trust, NIHR Wellcome Trust Clin Res Facil, Southampton, Hants, England
[4] Univ Hosp Southampton NHS Fdn Trust, Southampton NIHR Resp Biomed Res Unit, Southampton, Hants, England