We were lying under a sheet in a shack so humid that water was running down the walls. I hadn’t dared to open my rucksack for fear of unknown bugs getting in, so I lay in my damp clothes. I shut my eyes tightly and tried to sleep but all I could hear and feel was the gentle thud of large insects dropping off the ceiling and onto the sheet above me. It was then that I realized I needed to be violently sick. This night happened when I travelled through Sri Lanka some years ago.