Sexual transmission of HIV-1 among serodiscordant couples in Porto Alegre, southern Brazil.
BACKGROUND
A cohort of 93 heterosexual HIV serodiscordant couples with no prior antiretroviral use were identified in a large referral center from February 2000 to January 2006 in southern Brazil.


METHODS
Review of clinic records retrospectively identified 56 cases of untreated index cases whereas 37 couples were identified prospectively. Demographics, medical, and laboratory data were obtained. During follow-up, 41/93 index cases (44%) initiated antiretrovirals (ARVs) and from 52 without ARV use, 4 were lost to follow-up. Median viral loads were used to compare transmitters versus nontransmitters (Mann-Whitney test).


RESULTS
Sixty-seven (72%) index cases were female (49% identified during ante-natal care). Unprotected sexual intercourse as a risk factor for HIV-1 infection was significantly higher as compared to intravenous drug use (P < 0.0001) in female index partners but not in male index cases. Sexually transmitted diseases were identified in 22 cases (24%). Six HIV-1 seroconversions occurred (6.5%). In all cases index partners were not using ARVs at the time of seroconversion. Among 26 couples with a male index case, there were 4 seroconversions (15%) and among 67 female index cases there were 2 seroconversions (3%). All seroconversions occurred with virus loads >1000 copies/mL. Eight female index cases (22%) reported no condom use.


CONCLUSIONS
Heterosexual transmission occurred more frequently from HIV-infected males to females (rate ratio 3.5; CI, 95% 0.8-16.5 P = 0.259), although without statistical significance, probably because of the small sample. Transmitters showed significantly higher median viral loads (P = 0.042) suggesting that heterosexual transmission of HIV is more a function of viral load than gender of index case. ARV use may play a role in the prevention of HIV-1 heterosexual transmission. Other factors may be involved and should be further evaluated in larger cohorts.
Melo
Marineide Gonçalves
MG
Department of Infectious Diseases, Hospital Nossa Senhora da Conceição/GHC, Porto Alegre, Brazil.
Santos
Breno Riegel
BR
De Cassia Lira
Rita
R
Varella
Ivana S
IS
Turella
Maria Lourdes
ML
Rocha
Tauí Melo
TM
Nielsen-Saines
Karin
K
D001938:Brazil / Q000453:epidemiology; D005260:Female; D015483:HIV Antibodies / Q000032:analysis; D015658:HIV Infections / Q000453:epidemiology / Q000517:prevention & control / Q000635:transmission*; D018023:HIV Seronegativity; D015497:HIV-1; D020010:Heterosexuality; D006801:Humans; D015994:Incidence; D008297:Male; D012307:Risk Factors; D012747:Sexual Partners; D012749:Sexually Transmitted Diseases / Q000453:epidemiology / Q000517:prevention & control / Q000635:transmission*
D015483:HIV Antibodies