At the last possible moment the engine gave a cough and started. There must have been an angel in the carburettor.

What I remember now, so many years later, is the relief I felt as the boat moved away. We never referred to the incident afterwards. If I remember aright, we carried on fishing.

But there was also the time I took an HIV test. It was in the mid-1980s, when everybody still felt insecure. Despite all the assurances about how the virus was passed on, was there a possibility that it could infect people in some other way? Nobody could be certain, and opinions were divided on whether kisses could be infectious or not. In other words, there was a grey area around the assertion that HIV was a weak virus, could survive only for about twenty minutes at room temperature, and therefore that it was not so easy to become infected, one could avoid it by simple precautionary measures.

I took a test at the hospital in Ystad. The doctor asked me why I was doing this and I said I had no reason to believe that I had been infected, but that I was doing it "for safety's sake". He had no objection. I suspected that he had probably undergone tests himself, just "for safety's sake".

Afterwards, when I had had my blood sample taken and registered, when I was on my way home in the car, I suddenly felt scared. I was so shaken that I had to pull up. It was a wet day in the autumn. I got out of the car and felt quite certain that the result of the test would be positive. Nobody, least of all me, would ever be able to explain how it had happened. Perhaps I would be the first one to demonstrate that there really was a very large grey area blurring the convictions of medical science regarding how the disease was passed on.

The three days that followed were pure nightmare. Common sense told me that I had nothing to worry about. But I gave a start every time the telephone rang. I woke up each night and stared into the darkness.

The nurse duly phoned on the third day. A shiver ran down my spine when she said who she was. But, predictably, I was not summoned back to the hospital. She simply told me, with no appearance of feeling, that the test result was negative. I thanked her for informing me, perfectly calmly, with no trace of stress, and replaced the receiver.

Then I went out into the rain and fell to my knees in the mud. I stayed like that for a long time before going back indoors. My relief had been manically exaggerated. Not joy, just relief. I can still remember the mud sticking to my trouser legs.

I had been afraid for no reason. What must it be like for those who take the test and know that there really is a risk that he or she has been infected?

Moses was the only man with whom I had real conversations during my stay in Uganda. Beatrice, who worked with people with HIV, told me that men seldom write memory books. Nor were they so willing to talk about their fate, whereas women were always prepared to talk openly about their lives. But there were exceptions, and Moses was only one of many, even though for various reasons he was the only one I ended up talking to.

The last time I spoke to him somebody took a couple of photographs with a polaroid camera that I had with me. Moses and I are sitting on a couple of wooden stools in the shade of a tree. He kept one of the pictures, I kept the other. Whenever I look at it I wonder how he is, if he's still alive, if he's in pain. And I think that the picture shows him exactly as I remember him. A face radiating great dignity. A man who has accepted that life can suddenly change course, and nothing will ever be the same again.

Moses lived not far from Christine. He had a large family, several of his children had families of their own and some lived in the same house as he did. He sat in the shade, pointing out all his grandchildren and telling me their names, their ages; and he characterised their "lust for life" in various ways. One of them, a girl, delighted in kicking a home-made football around their yard. A boy, aged about ten, could climb any tree that stood in his path. He could climb as high as you like, as quick as a flash. That was the way he liked to characterise his grandchildren, and he would keep laughing out loud. But much of the time he was melancholy.

He had written about fifteen memory books, one for each of his children and some for the older ones among his grandchildren. He didn't tell me how he had caught the virus; but his two wives were dead, no doubt he had infected them, and they had both died before him. I thought several times that I ought to ask him. But I never managed to overcome my hesitation. And now it's too late.

I asked him about the memory books.

"Somebody told me about them. Beatrice. At first I thought they weren't for me, but I couldn't get them out of my mind. One day I went to that centre where people who have the disease can go for help and advice. I spoke to another man who was also ill. He showed me a memory book he had written for one of his daughters. That made me think I ought to do the same. Even if I'm not very good at writing. I thought I could tell the tale, and one of my grandchildren could write it down. All of them can read and write. So that's what I did."

We leafed through one of the memory books he'd written. All the text was in rounded, childish letters. Everything except his signature and an admonition to "always live honourably and work hard".

He noticed that I could see the text had been written by various hands.

"I thought that even handwriting is a memory of a person. My handwriting is poor, the letters jump all over the place, but it's my handwriting. When I'm gone, my grandchildren can remember that this is how their grandfather used to write."

Then he started talking about how the fatal disease that had taken possession of his body had crept up on him.

"It came in the night. Illness never strikes when the sun is shining. Diseases, especially those that are serious and kill or blind or deform people, always creep up on you during the night."

I asked him what he meant by that.

"The mosquitoes start whining at night. They only suck your blood from sundown until the sun starts rising again. Mosquitoes carry death, malaria. Snakes and predators also roam in the hours of darkness, even if we haven't had any lions or leopards in these parts for the last ten or even fifteen years. We are convinced that disease strikes you during the night."

"A bite in the neck from a leopard can hardly be called a disease!"

"Everything that kills, be it visible or invisible, is a disease as far as I'm concerned. I know that you Europeans talk about something you call 'death from natural causes'. For us Africans that is a very peculiar way of looking at what happens in the dark."

But then he suddenly seemed to have lost interest in discussing his view that the night is the realm of death and illness. Instead he started talking about when he first realised that there was a new disease that was dangerous and invisible.

He had just started talking when the heavens opened. We took cover and sat in a part of the large house that he had to himself. One of his daughters, Laurentina, was very fat but moved gracefully and quickly despite her huge body. When we came in, she disappeared behind a curtain made from cut-up, old skirts. It was dim inside the room. Moses sat down in a sagging armchair from which he could keep an eye on what was happening outside while he spoke.

He said: "I was still very young. It was 1974, the year before Amin came to power and ruined our country. My father used to go often to Kampala to buy cheap clothes with factory faults that he put right and then cycled round the villages and sold them. One day he came home and told us about one of the young men he used to do business with in the city: he was now ill. My father said he had grown very thin in a very short space of time. He had lost his appetite, the glands under his arms had swollen up and were very tender, and now he was getting sores all over his body. He had been to the doctor, who had been unable to tell him what he was suffering from, nor could he give him any effective medicine. My father was quite sure about what he was saying. He had a keen eye, a good memory, and he often was quite certain about things before anybody else realised that something had happened. That was exactly what he said: 'Something has happened'. His business contact, Lukas was his name, was suffering from a disease that my father was convinced was something quite new. 'It has crept up in the night,' my father said. Lukas died, and his two wives also fell ill and had the same mysterious sores and one after the other they too died. Every time my father came back from Kampala, he told us about other people who had died from this same disease. Soon, so many had fallen victim to the disease that everybody was talking about why people all of a sudden became very tired and very thin and then died. But nobody knew what it was. I think that was the situation until the 1980s – in any case Amin was no longer around when the disease was finally given a name and it was understood how the infection could be spread. I was no longer so young by then. My father lived to be very old, and of course he was not surprised to find that he had eventually been proved right. What his friend Lukas had died of was a new disease that had crept up on us during the night. He had noticed it before anybody else."