It’s more the former than the latter.
Other studies show that when most people who are HIV+ find out their status, they drastically reduce their risk behaviors that would otherwise potentially transmit the virus to others. What this study shows is that when HIV “cocktail” drugs were introduced in the mid 1990s, it didn’t seem to reduce the rate of transmission.

This may mean that prevention programs that teach both positive and negative people about the virus and how to protect themselves from spreading it seems to have worked, even though we’ve never funded prevention efforts to the scale they need to be.

Is it saying that HIV+ people aren’t giving the virus to people…

JUST BECAUSE. Or that the Virus, as in the physical BIOLOGICAL CELL (or whatever the classification is) is not transmitting?