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How Drug Resistance Occurs
Drug resistance occurs when HIV changes so that it can survive and grow even in the presence of antiretroviral drugs. Understanding exactly how HIV becomes resistant to medications is a complex subject, but it can be broken down into a few simple parts.
HIV is a virus that can make copies of itself very quickly -- up to 10 billion copies each day. In this process, the virus also has a bad habit of making genetic mistakes as it multiplies. These mistakes, called mutations, are never corrected and the result is that a person's HIV infection is actually made up of a large number of different types, or strains, of the virus.
The antiretroviral drugs available today can stop most, but not all, strains of HIV. So drug resistance develops when some of the mutant strains of HIV are able to survive in spite of treatment. Over time, these strains become the most common ones in a person's body. Then in most cases, viral load will go up, CD4 counts will go down, and the risk of getting sick increases.
The recommended next step is drug resistance testing to choose which antiretroviral drugs to switch to in order to stay ahead of the virus.
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