Since 1985 Medecins Sans Frontieres has been offering HIV and AIDS care for the most vulnerable people, those shunned by society and desperate through poverty in the slums and prisons of Lima. In a celebration of the organisation's work and of the people whose existence it has salvaged, Magnum photographer Larry Towell brings us a dynamic and stirring series of images.

In Peru the prevalence of HIV is low, but highest amongst the most neglected members of society. Since 2004 MSF has offered care in the slum of Villa El Salvador, and it has worked in Lurigancho, one of the most populated prisons of Latin America, where the risk of contracting the virus is five to seven times higher than in the rest of the country. At the end of 2007 MSF handed over all its Peruvian projects to local authorities, leaving after almost twenty-five years.

Towell was commissioned to travel to the prison and the slums and to photograph the result of that quarter-century presence, showing that the area is now ready to continue the fight on its own. Most of these pictures were taken in the week and a half culminating on International AIDS Day, 2007. He brings us black and white images of people shunned by society and desperate through poverty, their situation exacerbated by an epidemic endemic to an already marginalised population.