The USA's national health protection agency, known as the Centers for Disease Control and Prevention on
September 27, 2017,
officially released the historic report stating "When ART results in viral suppression, defined as less than 200 copies/ml or undetectable levels, it prevents sexual HIV
transmission." -Eugene McCray, MD CDC
This news is the motivator for the now commonly used term, Undetectable Equals Untransmittable.