By how much can lifestyle changes and antiretroviral medications reduce the transmission of HIV?

Antiretroviral medications, when taken consistently, can effectively reduce the viral load in an individual with HIV to undetectable levels. This is crucial because individuals who maintain an undetectable viral load cannot transmit HIV to sexual partners, a fact encapsulated in the phrase "Undetectable = Untransmittable" (U=U).

Moreover, lifestyle changes such as consistent condom use, reducing the number of sexual partners, and engaging in regular healthcare follow-ups can further mitigate the risk by enhancing overall health and reducing risk behaviors.

Research indicates that the combination of these approaches—maintaining adherence to antiretroviral therapy and implementing proactive lifestyle changes—can lead to a reduction in HIV transmission rates of around 90% or more. This significant reduction illustrates the effectiveness of a comprehensive strategy that includes medical and behavioral interventions in managing HIV transmission risk.

In the context of the other choices, while some levels of lifestyle changes and medication adherence can lead to reductions in transmission risks, they fall short of the nearly complete effectiveness reached through optimal adherence to treatment and healthy lifestyle adaptations. Hence, stating that transmission can be reduced by 90% reflects the most realistic and evidence-based understanding of the impact that effective treatment and preventive measures have on HIV transmission.