It's now more than three years since I met Pepile, but I still think of her often.

Samkelisiwe embraces her mother in the TB ward of Ngwelezane Hospital, Natal, South Africa. Their picture is one of over 1000 taken by Positive Lives, a collaboration bringing together photographers, charities and people living with HIV

She died of Aids soon after I met her.

I'll be thinking of her even more than usual over the coming weeks as the BBC launches a two-week season of programmes and online coverage devoted to the HIV epidemic.

Pepile was seven years old, and had been infected when her neighbour raped her. He thought that he would be cured of Aids if he had sex with a young girl.

She lived, and died, in South Africa, the country where there are more people living with HIV/Aids than anywhere else in the world.

Globally, the number of those infected is now more than 42 million; by the end of the decade it will have grown by another 45 million. Half of the people living with HIV/Aids are women; more than half are under the age of 24.

Stark statistics

Enough numbers? Here are some more: the populations of India, Russia and China make up half of the world's total population.

In all three countries, there are already clear signs of an Aids epidemic taking hold.

The race against what the UN Secretary-General Kofi Annan has called "the genocide of a generation" is a marathon, not a sprint.

Nearly a million people are believed to be infected in Russia; more than a million in China, between four and five million in India.

Every time I see those numbers, I think of Pepile. Her father and brother had already died of Aids by the time I met her: the estimate now is that there are 14 million children around the world who have lost one or both of their parents to Aids.

Hitting the poor

Perhaps you live in a country where Aids is under control. Lucky you.

But do you, or people you know, travel to countries where it is widespread? Do people from those countries come to where you live? Globalisation means that viruses can cross borders just as easily as people can.

It is, of course, the poorest countries that suffer most. But whereas in the past it was the weakest who died in epidemics-usually the very young and the very old-Aids is different.

It kills young adults: the producers, the parents, the farmers. If factory workers die, production falls. If parents die, children are orphaned and their education brought to a halt. And if farmers die, food production suffers, and those who are left behind go hungry.

Funds for the fight

In 1999, the world's richest countries made available about $300 m to fight HIV/Aids.

Within three years that figure had risen 10-fold to $3 billion. By 2005, it's estimated that at least $10.5 billion will be needed.

The money is needed to buy drugs, to enable people with HIV/Aids to live longer. It is needed to pay for education-to teach girls how to say no to unwanted or unprotected sex.

And it is needed to pay for health care, because all the available evidence shows that where basic health care is deficient, Aids spreads more quickly.

Wake-up call

There is, as yet, no known cure for Aids. But there are known ways to slow its spread and to reduce its capacity to destroy communities.

The race against what the UN Secretary-General Kofi Annan has called "the genocide of a generation" is a marathon, not a sprint.

When political leaders talk about it openly and honestly, when the world's richest countries wake up to the scale of the disaster, and when individual men and women learn how to change their behaviour to minimise the risk of infection - then, and only then, might we able to say that the race is being won.

Have your say

This BBC News Interactive and BBC World Service website - www.bbcnews.com/aids - will be offering a host of interactive debates, features, personal stories and information in the weeks running up to World Aids Day on 1st December 2003.

This is your chance to put your own questions to world experts and celebrities involved in the battle with HIV, and to share your experiences with our audience around the world.

We will be tackling issues ranging from the race to bring anti-HIV drugs to poor countries with impoverished health systems, to the mammoth task of changing sexual practices in communities where many people simply don't believe Aids exists.

We will be asking whether the world's leaders are doing enough-and what more they could and should be doing.