Occult hepatitis C virus infection during an outbreak in a hemodialysis unit in Thailand

Control of hepatitis C virus (HCV) in hemodialysis populations is a major public health priority, but the preferred methods to prevent and rapidly detect HCV outbreaks in these populations remains subject to debate. We enrolled 231 hemodialysis patients at three dialysis centers in Chiang Mai, Thailand. Patients were followed every 6 months for 3 years and tested for the presence of serum HCV antibody and HCV RNA at each visit. We additionally isolated and tested peripheral blood mononuclear cells (PBMCs) for HCV RNA collected at the 30-month follow-up visit. Fifty-one study participants negative for anti-HCV at the baseline enrollment visit sero-converted overthe course of the 3-year follow-up period. Of 11 individuals who transiently lost detectable serum HCV viremia, we were able to detect HCV RNA from the PBMCs of two individuals. Our results suggest that occult HCV infection may be common among hemodialysis patients, and serum HCV RNA testing may be supplemented with PBMC testing to maximize diagnosticsensitivity and aid in outbreak containment. Further work on the diagnostic implications of HCV compartmentalization in hemodialysis and other settings is urgently needed.