411   Sexual Transmission Can Precede Symptoms in Primary HIV-1 Infection.

C. D. Pilcher*¹, P. Vernazza², M. Battegay³, T. Harr³, S. Vora⁴, K. Ritola¹, S. Yerly⁴, C. B. Hicks⁵, J. J. Eron Jr.¹, and L. Perrin⁴.
Cantonal Hosp., St. Gallen, Switzerland;³Univ. Hosp., Basel, Switzerland;⁴Univ. Hosp., Geneva, Switzerland; and⁵Duke Univ., Durham, NC.

Background:Epidemiologic and virologic evidence suggests that primary HIV infection (PHI) is associated with high sexual infectivity. In order to define better the timing of sexual infectivity in PHI, we examined five cases of sexual transmission occurring during the PHI of the index case (IC) and resulting in PHI in an infected partner (IP).

Methods:Transmission pairs were identified from European and US cohorts offered HAART during PHI, as defined by a positive HIV RNA, DNA or p24 with a negative ELISA or a negative or evolving WB within 30 d of study entry. Likelihood and timing of sexual transmission between IC and IP were established by sexual history and exclusion of other risk factors. Phylogenetic analysis of pol sequences was performed for confirmation of transmission within each pair.

Results:1 male to male, 3 male to female and 1 female to male pairs were identified. All paired sequences gave a bootstrap value >99/100. Transmission occurred a median of 2 days prior to symptom onset in the ICs (range - 7 to +7 d). Onset of symptoms in 4 symptomatic IPs occurred a median of 19 d (12-20 d) after transmission. Median peak HIV RNA level for ICs was 6.0 log copies/ml (5.3—7.2 log); this was greater than for 46 unselected PHI patients (median 5.4 log; p = 0.04, Mann-Whitney-U). Other STDs were confirmed within 2 pairs. Semen HIV RNA was measured in one IC and exceeded blood level.

Conclusions:Individuals with symptomatic PHI may infect sexual partners as early as 2 days prior to the acute retroviral syndrome, or 10—18 days from infection. Both biological and behavioral factors in PHI may increase transmission rate. Targeted public health strategies to facilitate the identification, counseling and treatment of subjects with PHI should include rapid contact tracing for individuals with PHI.