Intermittent low-level viremia (LLV) can occur in the very early stages of primary HIV infection, before the ramp-up phase of HIV viremia, according to a new report.

The findings suggest a theoretical risk that infective plasma could bypass current screening methods, but such a risk would be small, contributing to an estimated 1 in 5 million cases, Dr. Michael P. Busch of Blood Centers of the Pacific in San Francisco and colleagues write.

“Pathogen reduction methods, already applied to the manufacture of plasma components and derivatives and in various stages of trials and development for other blood components, seem to offer the best chance to counter the small theoretic risk of HIV transmission during the very early period of the infection,” Dr. Busch and colleagues conclude in the June 1st issue of the Journal of Acquired Immune Deficiency Syndromes.

Dr. Busch and his team assembled 15 panels of serial samples from plasma donors who eventually developed HIV infection. In 6 of the 15 panels, LLV was identified in samples preceding the first sample with HIV-1 RNA levels above 100 copies/mL, and separated from that sample by at least one negative sample. The LLV tests occurred 9 to 25 days before the first 100 copies/mL sample appeared.

The researchers estimate that the “blips” represent an HIV plasma concentration of 1 to 10 copies/mL, well below the 1,500 copies/mL necessary for heterosexual transmission. It is conceivable, however, that plasma with this LLV could be infective if used for plasma or platelet transfusion, they note.

The finding “presumably reflects intermittent escape or leakage of small amounts of HIV from mucosal and lymphoid tissues near the entry site into the bloodstream or from rare circulating infected CD4+ cells,” Dr. Busch and his team write.

“This observation confirms the capacity for early spread and dissemination of HIV after mucosal penetration, a property that needs to be taken into account in vaccine development and in other strategies for prevention and early treatment.”

J Acquir Immune Defic Syndr 2005;39:133-137.