On 2 November 1955, I got a telephone call from Dr Le Roux of Knysna, a town about halfway between Port Elizabeth and Cape Town. He asked me if I would look after a patient, John Wiles, the son of a well-known South African painter. Dr Le Roux told me that the patient was already in an ambulance on the way to Port Elizabeth and asked me to arrange for his urgent admission to hospital because he was desperately ill with bilateral pneumonia.

John Wiles has given me permission to relate his story. He was employed by the Rhodesian Geological Service and told me that, five weeks earlier, he had been exploring a complex of caves in the Urungwe Native Reserve of Rhodesia to see if it was possible to use as fertiliser the large quantities of bat guano that were there. He had entered the cave with the Native Commissioner, a man named Dawson who knew the cave and who acted as a guide, and with a Mr Swartz. They spent the following day underground surveying the caves, which were connected by passages and were each several hundred feet long. The caves were occupied by thousands of bats, the common small variety and a larger bat with a wingspan of over two feet. The guano was very dry and was in places over six feet deep.

Twelve days later Wiles noticed a burning sensation across his chest; this discomfort worsened. He had a headache and thought he was developing an attack of malaria. The next day he took a train back to South Africa; during the four-day journey his symptoms increased. By the time he reached his father's home, at Knysna, he had a fever, his back and head were aching intolerably and he was unable to take a deep breath without pain and coughing. He called Dr Le Roux, who examined his blood for malarial parasites and trypanosomes, the organism that causes sleeping sickness, but no parasites were found in the blood smear. In spite of penicillin injections, Wiles's pain in his chest and his cough increased over the next two weeks.