Human immunodeficiency virus (HIV) is a virus that attacks your immune system, specifically your infection-fighting CD4 T cells. Once your CD4 T cell count drops below 200 cells per milliliter of your blood, your condition is considered to have progressed to acquired immunodeficiency syndrome (AIDS), the end-stage of HIV where you are at risk for serious, often fatal ifections. Today, treatment is so sophisticated that HIV should never progress to AIDS. However, treating HIV does not come without its fare share of challenges – the greatest of which being HIV drug resistance. You may think of drug resistance as your body becoming too accustomed to a drug or stimulant -- like coffee. After you’ve been drinking it for a while, one cup just doesn’t cut it. With HIV, it means something entirely different. HIV drugs work by clearing the virus from your bloodstream and preventing it from destroying your immune system. HIV therapy doesn’t completely eliminate HIV (we can’t cure HIV… yet), because the virus hides in a few cells in the body that the medications just can’t adequately access. But effective HIV therapy keeps the virus suppressed to a point where it can no longer function properly, in essence putting the virus into a dormant stage. If left untreated, however, HIV is anything but dormant. Unchecked HIV makes copies of itself (replicates) extremely rapidly, chewing up CD4 T cells in the process. Imagine copying a sequence of 10,000 letters by hand from one piece of paper to another, and doing it as quickly as you can, over and over again – you are likely to make a few mistakes here and there. Well, it’s no different for HIV. During the rapid replication process, the virus occasionally makes copy errors, known as mutations, which can cause slight changes in the shape of viral proteins. HIV uses these mutations to its advantage, because sometimes the mutated versions of the virus can resist the effects of HIV medications. Once the virus has mutated and become resistant to a particular medication, that drug will never work again to control your virus. Drug-resistant mutations have the potential to wipe out entire classes of HIV medications, making it extremely difficult to find another treatment regimen that works. Preventing Drug Resistance Quite simply, the most common reason for the development of HIV drug resistance is people not taking their medication as prescribed. Just a few missed doses may be enough for the virus to begin replicating at a high level again, and during this period of increased viral replication, the virus has the potential to create new mutations that might allow the virus to become resistant to your medications.Once resistant mutations develop to your regimen, that therapy will no longer be effective against your virus ever again. In fact, I tell my patients that taking their medication every day is the single most important thing they can do for their health and well-being. If you develop unexplained flu-like symptoms, such as fevers, sweats, body aches, and rash, you should see your doctor to have your viral load re-tested to make sure your virus has not developed drug resistance – even if you have been taking your medications as directed. While rare, resistance can develop while on appropriate therapy, sometimes because there were “hidden” drug-resistant mutations unknown at the time treatment was started, and sometimes because other medications or conditions may be hindering the effectiveness of your HIV therapy. Needless to say, communication with your infectious disease (ID) physician, and all of your physicians, is critical. If another doctor prescribes a new medication, or even a higher dosage for you, make sure to run it past your ID healthcare provider. To help ensure good communication, it’s important to see your ID provider often. I like to see my patients at least every 3-6 months to make sure their viral load hasn’t suddenly become detectable. If it has, there’s a good chance their virus has developed drug resistance. A genotype test will tell me if their virus has mutated, if that mutation is causing drug resistance, and then which medications are still useful against that virus. Bottom line? HIV should never again be a death sentence. Adhere to your medication and keep in contact with your doctor, and you will live as long a life as if you were never infected. And if there is any reason you can’t take your medication every day, whether due to side effects, financial trouble, life changes, or simply forgetting, let your doctor know. More times than not, there’s an easy fix to the problem – which is more than I can say for HIV drug resistance.