January 27, 2017
This week, a study estimates that the number of new HIV cases in the U.S. has steadily declined between 2003 and 2010, though the number of new cases remains around 40,000 a year. Another study finds that services for partners of newly diagnosed patients are most effective within 30 days of diagnosis. And drug resistance related to pre-exposure prophylaxis (PrEP) is rare, but more likely if individuals are taking emtricitabine and tenofovir disproxil fumarate (TDF) together compared to TDF alone, another study finds. Finally, research from Thailand suggests that a lower dose of atazanavir (Reyataz) may be just as effective as the current standard dose. To beat HIV, you have to follow the science!
A new method for estimating HIV incidence found a steady decline in new HIV cases between 2003 and 2010 in the U.S., the Journal of Acquired Immune Deficiency Syndromes reports.
Previous U.S. Centers for Disease Control and Prevention (CDC) estimates showed stable numbers for that period. The mathematical model used in this study is based only on reported HIV cases and does not distinguish between recently-acquired HIV and long-standing infections. Its results match those from another new model that was based on the CDC estimates and all-cause mortality data.
The Global Burden of Disease Study also estimates lower HIV prevalence than does the CDC. The results of this new method "suggest that CDC may have overestimated HIV incidence," study authors write. However, they caution that interventions to prevent HIV acquisition should be continued since there are still around 40,000 new HIV cases a year.
Partner services for those newly diagnosed with HIV who are in the acute or early stages of the infection (AEH) are effective in identifying people who may not know that they are living with HIV, a study published in AIDS found.
Such confidential contact tracing yielded the highest number of new HIV diagnoses when it was conducted within the first 30 days after the index case was diagnosed. One in seven newly diagnosed partners was also in the AEH stage and thus carried a high risk of transmitting the virus to someone else. The partners who had not acquired HIV reported behaviors that put them at risk for acquiring the virus. That group could be offered HIV prevention services, including PrEP, study authors note.
If resource limitations do not allow offering contact tracing to everyone, that service should be focused on people diagnosed with AEH within the past 30 days, study authors conclude.
Taking a combination of emtricitabine and tenofovir disproxil fumarate (Truvada, FTC/TDF) for PrEP rather than tenofovir (TDF) alone increases the likelihood of developing resistance to emtricitabine (FTC), if the person acquires HIV while on PrEP. However, the overall risk of developing an HIV mutation that prevents either of these drugs from working against the virus is quite low, a study of plasma samples from the 122 participants in the PARTNERS PrEP trial who seroconverted found.
The study, which was reported in the Journal of Infectious Diseases, used highly sensitive 454 sequencing to check for mutations in the virus known to confer resistance against the study drugs. The majority of participants who acquired HIV were not taking PrEP at the time of infection, according to the lab work. Of the 26 people who became HIV positive while taking PrEP, five developed drug-resistant mutations; three of these were already acutely infected with HIV when they were randomized to one of the two active PrEP arms, leaving two cases of breakthrough infections that developed drug resistance related to PrEP.
A lower dose of atazanavir (Reyataz) achieved the same level of viral suppression in Thai adults as the standard dose, according to a study reported in the Journal of Clinical Infectious Diseases.
Previous studies had shown that the concentration of standard-dose atazanavir (300 mg) is significantly higher in Thais than in whites. To determine whether a 200 mg dose of the medication would be sufficient for people in this ethnic group, the trial randomized 559 participants with HIV viral loads of less than 50 copies/mL to receive either 200 mg or 300 mg atazanavir, both boosted with 100 mg ritonavir and combined with two nucleoside/nucleotide reverse transcriptase inhibitors. After 48 weeks, 96.4% (lower dose) and 97.1% (standard dose) of volunteers still had viral loads below 200 copies/mL.
Furthermore, fewer people in the lower-dose group dropped out of the trial due to adverse events than did in the standard-dose arm. Study authors therefore recommend that the lower dose of the drug be routinely prescribed in Thailand for people whose HIV viral load is well controlled.
Warren Tong is the senior science editor for TheBody.com and TheBodyPRO.com. Follow Warren on Twitter: @WarrenAtTheBody.
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