'Test and Treat'-- A double-edged sword

The News in HIV the past few weeks has been the same message: Get people tested. Get people antiretrovirals.

It saves lives.



Test and Treat in Los Angeles: A mathematical model of the effects of test-and-treat for the MSM population in LA County.

This group of folks looked at a very specific question: What are the anticipated effects of ASAP HIV testing and ASAP antiretrovirals in the homosexual community of LA? If we start implementing this strategy now, in 2013, what will the HIV landscape in this community look like in 2023?

First, the good news--

The people who are HIV+, but dont know, could drop from 20% to 5%.

People in the community living with HIV (on meds)  increases from 62 to 76%. While this might look bad (more people with HIV/AIDS??), its actually good. The number goes up because the people progressing from HIV to AIDS drops 39%, and HIV/AIDS deaths drop 19%. More people will be living with HIV because fewer people would be dying.

But if HIV+ people are staying healthier and living longer, does that mean they will be infecting MORE people?  Nope! The model has new infections dropping 34%.

This is great news, right? Combined with all the stuff we learned earlier, GREAT NEWS!!

The great news comes at a cost.

Everyone is on meds.  No one completely clears the virus. Drug resistance develops. We know this.

So all of these good stats have to be looked at in light of this one--

The prevalence of multi-drug resistance HIV doubles. Up to 9%.

9% might not seem like that big of a number, not that big of a deal, but it is a BIG deal to the people infected with them. They have a limited number of antiretrovirals they can use. All the benefits of antiretroviral use? Go right out the window for these folks. When (not if) their virus becomes resistant to the rest of the available drugs, they are screwed.

Completely screwed.





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Does cycling anti-retrovirals have any effect on resistance? In other words, could you use cocktail A until resistance develops, then cocktail B, and then switch back to A after resistance to B develops?

By Kevin Bonham (not verified) on 22 Mar 2013 #permalink

Kevin, your plan works OK for individuals; its not a overly good idea from the point-of-view of population-based medicine.

Switching drugs from one where resistance has formed to another can help a patient. But at a population level it is a recipe for disaster - you re-enforce the resistant strain during drug withdrawal, meaning you improve your chance of developing multiply-resistant strains.

That later bit may not make a lot of sense. By its very nature, weaning off a drug means that the level of that drug in your body enters a range where mildly resistant virions can readily out-replicate non-resistant ones. This means you emphasize any resistance towards the drug you're withdrawing, all while adding in a new drug. The end effect is a burst of replication followed by a strong selective force - i.e. ideal conditions to select a partially resistant strain to the new drug, from a population resistant to the former drug.

The more 'obvious' option is to add in drug 'B' before withdrawing 'A'. That's not always possible (drug interactions, combined toxicity, etc), and even if possible can still create a selective effect for dually-resistant strains.

A thought regarding drug resistance:

What if we combined retrovirals with an extremely agressive approach to education about exactly how HIV is transmitted (i.e. the science behind it, more than just "sex"), as well as social programs giving free HIV testing to the population?

Would we be able to cut multi-drug resistance off at the pass, so to speak, and drop HIV infection rates to extremely low levels, and perhaps almost completely eliminate it?

By Metalogic42 (not verified) on 22 Mar 2013 #permalink

Abbie, thanks for sharing your knowledge with the rest of us... and for working for the betterment of humankind. (That sounded really lofty, but "you're too cool for words" seemed less poetic. ; )