The disease is caused by a protozoan parasite. Called Sarcocystis, it is common amongst animals – both wild and domesticated – and tends to occur in tropical and sub-tropical countries. There are two types that have been observed in humans – muscular and intestinal – and the current outbreak is of the muscular type. Humans can pick up the infection by eating food that has been contaminated by faeces from an infected animal; the parasite reproduces and forms cysts within muscle tissue. When symptomatic, people can suffer from fatigue, fever and muscle pains. Travellers are advised to observe scrupulous personal hygiene – all meat should be thoroughly cooked before it is eaten, and freezing meat prior to cooking can kill the parasites.