Using data from the Population-based HIV Impact Assessment (PHIA) surveys conducted in Eswatini, Lesotho, Malawi, Namibia, Tanzania, Zambia, and Zimbabwe from 2015 to 2017, the researchers estimated that close to 40 percent of children aged 1–14 years of age who are living with HIV across these seven countries were undiagnosed, amounting to 166,000 children living with HIV who were not diagnosed or on antiretroviral therapy (ART).