Intercell is offering free flights and hotel accommodation up to the value of 1,600 (£1,400) to 900 volunteers who are prepared to test a remedy for one of the most common holiday afflictions - travellers' diarrhoea.  
 
In the "Trek Study", willing backpackers who develop travellers diarrhoea will be paid to attend a clinic and injected with a new agent to see how they react, the Independent reports.