Aida was nowhere to be seen for the rest of my long conversation with her mother. It was almost afternoon, when we had to leave to drive back to Kampala and had other appointments, before I saw Aida again. She was with Christine's mother and some of the other girls, not Christine's daughters but the daughters of her sister. One sister had already died of Aids. They were preparing dinner. I watched Aida fetch the vegetables that Christine's father had been peeling all day.

Christine said:"When I'm gone, Aida will have to take on a lot of responsibility. I am trying to live for as long as I can for her sake."

"Does she know about it?"

Christine looked at me in surprise.

"Of course she knows about it."

"What did you tell her?"

"What had to be said. She will become the mother of her brothers and sisters, and if my parents are still alive she will become their new daughter once I'm gone."

"How did she react?"

"She was distressed. What else would you expect?"

We went to the car that was parked in the shade of some tall trees whose name I have never managed to remember. I had said goodbye to everybody, and worked out that Christine's family comprised sixteen people. Christine, who had been a schoolteacher and still worked whenever she had the strength, was the only one in this large family who had any income, and even that was extremely modest. She had a very direct way of assessing her wages in relation to her own fate.

"The monthly cost of antiretroviral drugs is precisely twice what I earn."

She shook her head before continuing.

"Obviously, you have to ask yourself if it is the drugs that are too expensive, or if it's me who isn't earning enough. The answer is straightforward. My small wage has always been sufficient to feed my family, but it's not enough money to save me from death."

So Christine wasn't taking any medication at all. She said she felt more weary now than she had done the previous year. She had been feeling ill for seven years. When her husband suddenly began losing weight and fading away, she knew. The day after her husband died, she went for a test. The result was no surprise. She kept everything to herself for a year. Then she told people, first her sister and then her mother. Whereupon her sister told her that she too was ill.

"I told Aida once she had celebrated her thirteenth birthday. I noticed that the disease was beginning to affect me. It was no longer dormant in my body. It had started moving."

"What did she say?"

"You've asked that already. She said nothing. She was distressed. I believe she already knew that I was ill."

"How could she know that?"

"Aida's a bright girl who listens to what people are saying. And she's not afraid to ask. But most important of all is that she doesn't believe all those people who say that this disease does not even exist."

We had reached the car. The driver was asleep. Flies were buzzing around, there was a smell of crushed banana and wet soil. Christine looked at me.

"You are not surprised? You must know that lots of people, many too many, still think there is no such disease as Aids. Or else they think it's a disease they can get rid of in various terrible ways."

I nodded, because I did know.

When we drove off, Aida was standing with a huge pan in her hand. Christine waved, as did her mother and other members of the family. Aida didn't wave because she was holding something in her hand. But I knew even then that I would be returning.

How can you sometimes know things you don't know? You just know.

That evening I thought about what Christine had said. About all those people who still refused to accept that there was such a disease as Aids. And those who did not deny the existence of the disease, yet maintained that there were strange and wondrous ways of curing it. I remembered a sign I'd seen fifteen years before in Zambia, somewhere between Kabwe and Kapiri Mposhi. "I'll repair your bike while my brother cures you of Aids."

I thought about what is happening in South Africa right now. The incidence of rapes has been growing for a long time. Until only a few years ago, most of the rape victims were grown women, or at least teenagers. Not any longer. Since 2001, in some parts of the country, there has been an increase in the number of rapes of children, and most repugnant of all: rapes of infants. This has to do with the widespread, lunatic belief that you can be cured of Aids by having intercourse with a virgin.

How can one fight such mad ideas? People are desperate. How will it be possible to control the Aids epidemic if people continue holding such impossible beliefs?

Christine had talked about her work. About her work as a teacher of the next generation.

She said: "Every time I face my class, it's as if my vision becomes blurred. The same as it is with my father's eyes. Sometimes he complains – although he is not the complaining kind – that everything round about him seems to be duplicated many times over. He sees ten of me, and just as many of my mother. It's the same with me when I'm standing in front of my pupils. Despite the fact that I don't have a problem with my eyesight. Not yet, anyway, although I know that many people with Aids go blind before they die. I see my pupils multiply before my eyes. And I see all the children who have not yet become my pupils. All those who will never learn how to read and write. Being able to read and write means being able to survive. How else can you find out how diseases are spread, how else can you learn how to protect yourself and survive? Of course medicines are important, of course I wish my wages were sufficient for my treatment. But it's just as important that all the children I see as blurred images have access to the knowledge that could save them from an all-too-early death. I want them not to have to write memory books for their own children because they die so young."

That is what Christine said. Several times. She wanted me to remember. That's why she kept repeating it.

Memory books. Writings as death approaches, about death and about life.

This is what this text I am writing is supposed to be about.

I did not go to Uganda so that a girl named Aida would show me the mango plant she tended with such care and concealed under a pile of twigs so that the family's pigs wouldn't gobble it up. I had travelled to Uganda to meet people who were preparing for death by writing little books for their children.

I do not recall the first time I heard about these memory books, but I recognised straight away that they were something I ought to find out more about. These memory books, small exercise books with pasted-in pictures and texts written by people who could barely recite the alphabet, could prove to be the most important documents our time has produced. When all the official reports, minutes, balance sheets, poetry collections, plays, formulae for the control of robots, computer programmes, all the archive materials that represent the foundation on which our life and our history is based – when all that has been forgotten, it could be that these slim volumes, these memoirs left behind by human beings who died too soon, prove to be the most significant documents of our epoch.

Five hundred years from now, what will be left from our time and the ages that preceded us? The Greek tragedies, of course, Shakespeare, and a few other things. Most treasures will be lost, and if not completely forgotten, then kept alive only by a tiny minority. But these memory books could well live on and tell future generations about the terrible affliction that affected our age, that killed millions of people and made millions of children orphans.