Torque teno virus in the lower respiratory tract: association with immunosuppression but not mortality in severe pneumonia—a multicenter retrospective cohort study - Xian Zhang; Lifei Chen; Fang Wang; Xiaofang Xu; Yueming Wu; JunLong Xu; Yongan Xu; Xuwei He (European Journal of Clinical Microbiology & Infectious Diseases, 2026)