[1] Inst Hlth Carlos III, Natl Ctr Microbiol, Unit Viral Infect & Immun, Madrid 28220, Spain
[2] Hosp Univ Valme, Unidad Clin Enfermedades Infecciosas, Seville 41014, Spain
[3] Hosp Univ Marques Valdecilla, Gastroenterol & Hepatol Dept, Santander 39008, Spain
[4] Univ Cantabria, Sch Med, Inst Valdecilla IDIVAL, E-39005 Santander, Spain
[5] Univ Complutense Madrid, Internal Med Serv, Univ Hosp Infanta Leonor, Sch Med,Gregorio Maranon Hlth Res Inst, Madrid 28009, Spain
[6] Inst Hlth Carlos III, Unidades Comunes Cientif Tecn, Bioinformat Unit, Madrid 28220, Spain