Early treatment may not be early enough

Giving monkeys antiretroviral therapy from just three days after exposure to simian immunodeficiency virus does not prevent a subsequent rebound of viral replication, suggesting that viral reservoirs are established early. See Letter p.74 Reservoirs of virus infection, impervious to antiviral drugs, are a serious obstacle to attempts to eradicate human immunodeficiency virus type 1 (HIV-1). Dan Barouch and colleagues explore the timing of the formation of these reservoirs in a monkey model. They find that antiviral treatment as early as three days after infection of macaques with simian immunodeficiency virus — prior to the onset of viraemia — fails to prevent the seeding of viral reservoirs, and the virus eventually rebounds when drug treatment is discontinued.