Yes, the virus can become detectable again if someone with HIV stops taking their medication. This means that they can share HIV with others through sex or sharing needles. Periods, where the virus becomes detectable again, are sometimes referred to as viral "blips". Blips are when HIV levels are minimally detectable for a short time and then return to being undetectable. Even when people take their HIV medicines every day, they may experience viral blips. Viral blips are usually the result of problems with the testing equipment, but sometimes they are due to an actual increase in viral load due to another illness or receiving a new vaccine that strains the immune system. Viral blips, in which the viral load drops back to undetectable quickly, are harmless. There is no significant risk that a person with a viral blip will transmit HIV to others.