Prevalence of antiretroviral therapy in the U.S.A. / transmission risk
Oct 17, 2010
First let me say that I admire the work you do in educating the public on this issue.
I have a twofold question for you concerning the real probability of becoming infected with HIV via a single heterosexual encounter. This question is in no way meant to undermine the advice you consistently give about practicing safe sex, it is only meant to help myself and others understand the real risk of HIV acquisition through unprotected vaginal sex.
I have read a number of large long-term studies looking at HIV transmission in couples with one infected and one uninfected partner which seem to suggest that if the infected partner is on a regimen of antiretroviral treatment, the risk of transmission to the uninfected partner plummets even when consistently practicing unprotected sex. In one such study that took place in Spain, not a single transmission took place.
So my twofold question to you is - in the United States what is the prevalence of women with HIV who are on antiretroviral drugs? And, if a woman is on antiretroviral drugs, what is the real risk that she would transmit HIV to her partner after a single exposure? Based on the studies I have read, it would seem to be far less than the 1/1000 or 1/2000 numbers often sited.
Thank you in advance for your response and keep up the good work.
P.S. As a side question, if antiretroviral therapy really almost negates the likelihood of transmission, could giving all HIV positive people the treatment result in the burnout of the epidemic?
Response from Dr. Frascino
When effective combination antiretroviral therapy is used consistently and drives the plasma HIV viral load to undetectable levels for at least six months, it is indeed true that the risk of HIV transmission is significantly decreased; however, the risk is not completely eliminated for variety of reasons.
As for the "real world" experience of using HIV treatment as prevention, the results are mixed. See below.
Prevalence data on HIV-positive women on antiretroviral therapy is difficult to obtain. Please note not all prescribed antiretroviral therapy results in suppression of the viral load to undetectable levels and even if treatment does knock HIV viral load in the blood into the undetectable range, it's still possible to have detectable virus in semen/ejaculate or vaginal fluids. Also, approximately 20% of the over-one-million HIV-infected folks in the U.S. have absolutely no idea they are infected with the virus.
That said, in my opinion, widespread or universal treatment of HIV of those who are infected would be an overall effective prevention strategy to decrease the number of new infections in a community.
Does 'real world' study cast doubt on use of HIV treatment as prevention? TREATMENT AS PREVENTION Michael Carter Published: 07 October 2010
Treatment with antiretroviral drugs did not reduce the rate of HIV transmission in serodiscordant heterosexual couples in the Henan province of China, investigators report in the October edition of the Journal of Acquired Immune Deficiency Syndromes.
The transmission rate in couples where the HIV-infected partner was taking antiretroviral treatment was 5% compared to a rate of 3% in other couples.
In an accompanying editorial, Dr Myron Cohen says that the results "demand a giant pause" and show that the ability of HIV treatment to reduce the risk of transmission outside the setting of clinical studies is uncertain.
However, the investigators note that the high transmission rate seen in couples where HIV treatment was used could be due to poor adherence. A separate study showed that 66% of patients in Henan province had sub-optimal adherence to their HIV treatment six months after starting HIV treatment.
Henan province has a high number of HIV infections due to unsanitary procedures for collecting commercial blood donations. Thousands became infected with HIV after selling blood at clinics with poor infection control methods.
The quality of HIV care in some parts of China has been questioned, owing to high rates of treatment failure and drug resistance reported in the country compared to treatment programmes in Africa and Latin America. China Daily reported in 2004 that many patients stopped taking antiretroviral drugs after a few months due to a lack of attention to side-effects by health care professionals.
The study published this week involved 1927 serodiscordant couples. HIV incidence was retrospectively monitored between early 2006 and the end of 2008. Individuals were interviewed about their HIV risk behaviour.
The patients contributed a total of 4918 person-years of follow-up (median, 2.8 years). There were 84 seroconversions (4%). This provided an incident rate of 1.71 per 100 person-years.
Sex in the previous three months was reported by 91% of couples where transmission occurred compared to 83% of those where it did not (p < 0.05).
More frequent sexual intercourse was also associated with an increased risk of transmission. The transmission rate was five times higher in couples having sex four times or more a month than in couples where intercourse was less frequent (RR = 5.24, 95% CI, 2.55-10.77).
Consistent condom use was reported by 93% of couples. Not using condoms was significantly associated with an increased risk of transmission (RR = 8.42; 95% CI, 4.83-14.67).
Only seven individuals reported extra-marital sex, and one of these seroconverted. Only one patient reported injected drug use, but this individual did not contract HIV. None of the men surveyed reported sex with another man.
A total of 1369 patients (80%) were taking HIV therapy. There was no significant difference in the transmission rate between couples where antiretroviral therapy was used and those where it was not (5% vs. 3%). No information was provided about viral load.
However, the investigators did find that the 266 patients who had switched antiretroviral therapy were less likely to transmit the virus to their partners than the patients who remained on the same regimen for the duration of the study (RR, 2.66; 95% CI, 1.15-6.15).
Finally, the investigators found that poor psychological functioning was associated with an increased risk of seroconversion.
"The incident rate from our study is similar to the incident rate of 2.3 per 100 person-years reported among a cohort of injecting drug users from a high prevalence region in southwestern China", comment the investigators. They add: "This suggests that HIV-negative spouses living in serodiscordant relationshipscould be considered one of China's high-risk groups."
Dr Cohen suggests that the study could have wider implications, and should cause those who advocate the use of treatment as prevention to "pause".
"Will ART suppress transmission of HIV under 'real life' conditions?", he asks, "it seems wise to try and answer this question before we fully deploy a 'Test and Treat strategy', expecting to detect a benefit to the general population."
However, increasing the number of patients taking HIV therapy in routine care has already been credited with falls in HIV incidence in San Francisco and British Columbia.
Wany L et al. HIV transmission among serodiscordant couples: a retrospective study of former plasma donors in Henan, China. J Acquir Immune Defic Syndr, 55: 232-38, 2010.
Cohen MS HIV treatment as prevention: to be or not to be? J Acquir Immune Defic Syndr, 55, 137-8, 2010.
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