Treating HIV very early can shrink the viral reservoir, or long-lasting pool of hidden infected cells, by 99%. Antiretrovirals do not reach this reservoir, so they cannot cure HIV. Researchers analyzed blood and tissue samples from 170 people in Thailand who had acquired HIV within the past two weeks and started antiretroviral therapy a median of two days after diagnosis. Participants who started treatment during the earliest stages of acute infection (known as Fiebig Stages I to III) showed a steep decline in the number of infected cells. The rare ones that persisted were mostly found in the gut and lymph nodes. In contrast, starting antiretrovirals later, during chronic infection, only slightly reduces the reservoir. Since people who start treatment very early have viral reservoirs 100 times smaller than those who start antiretrovirals later, it may be easier to eradicate these “mini-reservoirs” using various cure approaches, says senior study author Nicolas Chomont, PhD, of the University of Montreal Hospital Research Centre.