Long-haul travel is now at record levels among Britons, having grown by 52 per cent since 1987. In the early days of package tours, the only health risk was a touch of Benidorm belly, but today's travellers are exposed to a whole new range of sometimes lethal diseases: malaria, yellow fever, dengue, hepatitis, typhoid, Japanese encephalitis and rabies.
According to researchers, many travellers are getting on to the plane without the tablets, vaccines or knowledge needed to protect them from often lethal diseases, because travel agents are failing to warn them of the dangers.
Covert researchers who asked more than 200 travel agents about package holidays in Kenya and a flight to India found that six out of 10 agencies gave no spontaneous warning about health risks for the areas involved. (In Kenya the main risk is from malaria; in India, diarrhoea is suffered by one in two travellers and can ruin a holiday.) Even after prompting, only 70 per cent of agencies offered general health advice, says Dr Ron Behrens, consultant in tropical and travel medicine at the Hospital for Tropical Diseases, London, and co-author of a report on the research with Peter Grabowski of the University of Luton.
"It shows that travel agents provide health advice inconsistently and mention health risks only when prompted. For travellers' safety the industry needs to draw attention to health risks associated with its products consistently and effectively," they say in their report.
Dr Behrens says that travel agents are legally obliged to give information about all aspects of the product they are selling, including any hazards or risks. "Yet most travel agents simply do not take it upon themselves to warn people. The travel industry does not want to frighten people off. Of course they should not give specific health advice, but they should point out the risks and get people to seek further advice, either from a GP, travel clinic or chemist."
The people most at risk, according to Dr Behrens, are "novice" travellers - people who used to visit Benidorm but now go to the Gambia, and are travelling to tropical areas without taking any health precautions. "It happens regularly," he says. "We don't know the figures but any flight will have a number of people who simply haven't been told about vaccines or tablets they need."
The Independent's travel editor, Simon Calder, has read the study, and agrees it gives cause for concern. But he has reservations about the researchers' conclusions: "None of the covert encounters ended with the sale of a holiday, so I'm not sure that the research tells the whole story. I've just bought a package to the Gambia, and when I paid for it the travel agent warned me of the health risks and then insisted that I signed a form saying I'd been told. In my experience, this is standard practice for any travel agency that wishes to avoid being sued."
A spokeswoman for the Association of British Travel Agents says, "Clearly a travel agency is not a doctor and people may want to speak to a doctor for specific advice relating to the individual which can differ between people. We have worked with the Hospital for Tropical Diseases on a tropical health line number which provides information for countries around the world. Ultimately, one should seek medical advice."
In response to the urgent need for advice, the Hospital for Tropical Diseases has now launched a course in travel medicine for GPs and specialist nurses - the second of its kind in the world. "Doctors and nurses have never received any proper training in this area," says Dr Behrens: "All they do is look at a list - the expertise isn't there. People need not only advice about vaccines but also knowledge about how to prevent diarrhoea, skin infections and insect bites, and advice to practise safe sex." The hospital is expecting 80 professionals to start a week-long session in September.
Easily the biggest health risk for British travellers abroad is of being involved in a road accident, but among diseases malaria is the most harmful. Around 2,500 people a year are treated for malaria in Britain, although doctors believe the real figure could be twice that, because of under- reporting. The incidence of the disease has increased significantly since the Seventies when there were only a few hundred cases annually.
"The bugs we have are becoming more resistant and more people are exposed to them because more of us are travelling to tropical parts. There is improved transport, people have more leisure time, and transport is cheap," says Dr Behrens. Professor David Bradley, director of the Malaria Reference Laboratory of the Public Health Laboratory Service, says: "In a year or so there may well be some improvements in what is available for chemoprophylaxis. People are working on treatments which are more effective and with fewer side-effects."
Dengue, or breakbone fever, is a mosquito-born infection and one of a new wave of so-called emerging viruses sweeping the tropics. It can be fatal, particularly among children, and has spread from central and south America to parts of the US. London's Hospital for Tropical Diseases now handles around 20 cases a year.
Disease is not the only risk tourists face on long hauls: the flights themselves can be a health hazard. Inactivity during a long flight increases the risk of deep-vein thrombosis, with pregnant women among those at risk. The Drugs and Therapeutic Bulletin warns that stress and excitement can trigger angina, and people on medication can run into problems due to confusion over changing time zones.
Cabin pressure at 35,000ft can cause pain and perforation of the eardrum if tubes are blocked; in patients who have recently had surgery, internal gas expansion can cause pain and stretch or even burst stitches.
But despite such health hazards, the unstoppable trend in travel is to places where risks are high. And for most people, the pleasure outweighs the potential painn