I once asked my boss if we shouldn’t be out helping the poor and the sick, rather than searching for the meaning of a dot inside a bug that was almost too small to see.

‘The poor and the sick will always be with us,’ he said, ‘but we will change the way people think about the world.’

He had a point, I suppose. But when I looked around me and saw a lab full of people muttering recondite gene-speak under their breath like prayers, it all began to seem very strange.

Our group of Americans looked up to this man, but I don’t know how he felt about us. He told us, perhaps only partly in jest, that they talk about two kinds of Aids in Uganda: slim Aids and fat Aids. People with slim Aids get thinner and thinner and thinner until they finally waste away. Fat Aids afflicts doctors and bureaucrats who get enormous research grants and fly around the world to exotic places and get fatter and fatter and fatter. Fat Aids has become so common in Uganda, he told us, that if you say you are working on HIV people think you are a thief.