You're listening to the inquiry on the BBC World Service with me, Sonia Soda.

Each week one question, four expert witnesses and an answer. 25 years ago, AIDS looks set to become one of the biggest existential threats to human health.

Infection rates for HIV, the virus that causes AIDS, were rising.

And by the early 2000s, almost 2 million people a year were losing their lives to the

disease.

But then, it looked as though the tide was starting to turn. Hope grew that humanity

might be able to beat the deadly virus that has caused so much human suffering.

Four years ago the United Nations announced an

ambitious new goal that would have once been unthinkable to eradicate AIDS as a

public health threat by 2030.

It was a bold ambition, but was it too bold?

As experts gathered for the latest international AIDS conference in Amsterdam last month,

the optimism has started to wane.

A man synonymous with the fight against HIV and AIDS,

Professor Peter Piot, told delegates.

We are not on track to end the HIV epidemic.

We've made enormous progress, but we also feel that the discourse on ending AIDS has bred a dangerous complacency.

The facts are there.

And the facts are stark.

Once falling death and infection rates have flatlined,

and in some parts of the world they've even gone up.

So in this week's inquiry we're asking,

...