Simian varicella virus (SVV) DNA was detected in blood mononuclear cells (MNCs) of adult African green monkeys 7 days to 23 months after intratracheal inoculation with 10(3) plaque forming units. Infectious virus was not detected in MNCs at 14 months postinfection (p.i.), and electron microscopic (EM) analysis of MNCs from two monkeys 21 months p.i. did not reveal virus particles. Real-time quantitative PCR analysis of DNA from blood MNCs taken at multiple intervals from SVV-infected monkeys M7 and M8 revealed a 10- to 100-fold decrease, but not clearance of SVV DNA in MNCs between 11 and 17 months p.i. Thereafter, the SVV DNA copy number did not decrease further between 17 and 23 months p.i. PCR analysis of MNCs sorted by flow cytometry revealed SVV DNA in T cells (CD4(+), CD8(+)) and B cells (CD20(+)), but not in monocyte-macrophages (CD14(+)), 10 days p.i. At 11 and 23 months p.i., SVV DNA was found exclusively in CD4(+) and CD8(+) T cells. Whether the detection of SVV DNA in CD4(+) and CD8(+) MNCs many months after the resolution of acute varicella reflects continued infection of these cells that began at the time of acute varicella or represents infection acquired by MNCs trafficking through infected tissues is unknown.