Whether a person is travelling abroad for business or pleasure or is going to live in another country, he or she should obtain information about the climate, environment and health risks at their destination (including any stopovers that involve personal contacts with local people). Certain risks to health in another country may always be present; sometimes hazards to health may be temporary because of a local epidemic or sudden adverse environmental circumstance, such as a drought, earthquake or volcanic eruption, any of which can cause problems in obtaining supplies of food, clean water and medicine. Any intending travellers with an existing illness should find out from their doctors whether they are fit to travel; whether the country of destination will admit them; whether they will be able to obtain appropriate treatment; and if so, how it will be paid for. Healthy travellers are also advised to enquire about health-care arrangements (including payments) in their destination country in case they fall ill while away. Some countries have reciprocal arrangements with the UK. Travellers should take sensible precautions about drinking water and food, as hygiene standards vary widely throughout the world. Pharmacists are usually helpful with advice on over-the-counter remedies for travel sickness and traveller’s tummy. Recent media publicity has alerted air travellers, especially those flying long distances, about the risks of developing deep vein thrombosis (DVT), sometimes called ‘economy-class syndrome’. Sitting in a relatively confined position for several hours can cause blood clots to form in the deep veins of the legs: ocasionally small clots break away and are carried in the bloodstream to the lungs where they form clots in the circulation called pulmonary emboli (see PULMONARY EMBOLISM) – a potentially fatal disorder. The risk of developing DVT is greatly reduced by exercising the feet and knees while sitting, by walking around the aircraft when possible, drinking plenty of water but little or no alcohol, and wearing (properly fitting) elastic stockings on the legs. Anyone who has already had a DVT should seek medical advice before travelling by air. Travel agents have a responsibility to advise their clients about health risks, and the travel trade has access to directories giving up-to-date information on visa requirements, recommended immunisations (see VACCINE; IMMUNISATION), climate, current health hazards and currency allowances. They cannot, however, be expected to give detailed individual advice, especially if the traveller has an existing medical condition. There are many publications of help to travellers, and authoritative advice is available from organisations listed in this appendix. Travellers returning home who fall ill – even several months later – should always tell their doctor where they have visited and when, in case their illness originated in another country.