A necessity: Biodegradable soap. Avoid disease without damaging the environment.

A luxury: My Nokia phone, because I can e-mail and fax from it wherever I am in the world. I'm the sort of person who wants to be in contact when I'm away.

A memento: A necklace of Nyame Nyame, the Zimbabwean river god.

If only: There is a bag that you just throw into a dirty pool and it filters clean water into the bag. If only all travellers took one with them, then people would not pick up water-borne disease.

• Dr Charlie Easmon is a specialist adviser in travel health at the Hospital for Tropical Diseases Travel Clinic, London. Travellers' Advice Line: 09061 337733.