FIG. 3.

Viral burden in plasma during primary infection. The viral burden, as determined by competitive RT-PCR, is expressed as the number of copies of viral RNA per milliliter plasma. The dotted line, denoting plasma samples for which viral RNA was not detected, is placed at 2,860 copies/ml, which corresponds to the threshold of detection when plasma was diluted 1/2 (see Materials and Methods). Since plasma samples collected at 3 weeks had to be diluted 1/10 as a result of an inhibitory substance, the viral burden in the three 3-week samples for which no viral RNA was detected must be considered to be less than 14,300 copies/ml of plasma. Plasma samples for which viral RNA, although detected, was present at less than 30 copies per reaction are denoted by a dashed line, corresponding to 8,580 copies/ml of plasma.