Dynamics of SEN virus infection among injection drug users.

SEN virus (SENV) is a recently discovered group of DNA viruses whose members (SENV-D and SENV-H) are linked to posttransfusion hepatitis. Of 397 injection drug users (IDUs) in Baltimore, Maryland, SENV-D infection was detected by polymerase chain reaction in serum samples from 130 (32.7%) and SENV-H infection in 149 (37.5%). Of 41 IDUs in whom SENV-D DNA was initially detected, retesting for viral persistence a median of 9.3 years later detected SENV-D in 25 (61.0%), whereas SENV-H was detected on retesting in only 14 (26.9%) of 52 IDUs in whom the virus was originally found. Reinfection was apparent (>5% nucleotide difference) in 77.8% of IDUs who repeatedly tested positive for SENV-D DNA and in 55.6% of those who repeatedly tested positive for SENV-H DNA. Among Baltimore IDUs, SENV-D and SENV-H infections are common and dynamic, including both viral clearance and reinfection. The clinical significance of SENV infection in this setting remains unknown.