Malaria is now being brought back by increasing numbers of people returning from long-haul holidays in Africa, South America and South-east Asia, and doctors suspect that, in many cases, people have stopped taking prescribed medication either because of side-effects or the fears of them.
And with more than 250,000 people going on long-haul holidays this Christmas, there are fears that there may be a record number of cases of the disease. In the last year, 10 people in Britain have died of malaria, and over 2,000 cases have been reported, double the number that was treated 20 years ago.
Malaria is a disease caused by a parasite in the red blood cells that is passed on by a bite from an infected mosquito. Classic symptoms are periodic attacks of chills and fever, but it can also produce fatal complications, affecting the liver, kidneys and brain. It is one of the world's biggest health problems, with 500 million cases a year and 2.7 million deaths.
It is endemic in many areas. The first line of defence is to prevent mosquitoes from biting by using repellents and mosquito nets. But for most people, protection will come from using one of four different antimalaria drugs: mefloquine, chloroquine, proguanil or maloprim. Which particular drug is appropriate varies with the area being visited and with the prescribing doctor.
Although there is a risk of side effects and the drugs do not give 100 per cent protection, one estimate is that, in the UK, the use of mefloquine alone prevents around 3,000 cases of malaria a year, saving 11 lives and pounds 22m in hospital treatment costs.
Although in most cases any side effects are relatively minor compared to the potential effects of the disease itself - ranging from nausea and dizziness to panic attacks and mouth ulcers - doctors are increasingly concerned that people are not taking the drugs because of adverse publicity.
"Antimalaria drugs have a bad name which, on the whole, is undeserved, and I believe it has a big impact on the use of them and on the protection people are getting. People need to take professional advice, see their GP or go to a travel clinic," says Dr Ronald Behrens, consultant in travel medicine at the Hospital for Tropical Diseases in London.
The concern is supported by evidence from an audit of patients at his hospital, reported in the British Medical Journal, which found that 80 per cent had either not taken antimalaria drugs or had not taken them properly. In some cases they had been given the wrong medical advice because of confusion over antimalaria medication.
A 50-year-old woman who was admitted to the hospital with liver failure and haemorrhaging had been told by a GP practice nurse that antimalaria drugs had too many side effects. Instead she had opted for a homoeopathic solution which failed to protect her.
A 55-year-old man, admitted on Christmas Eve last year, contracted malaria after his own doctor advised he stop taking the antimalaria drugs while he was in Nigeria. He developed malaria and liver failure. A 37-year- old woman who was treated for fever, jaundice, shock and a reduced level of consciousness had decided not to take her medication when she went to the Sudan.
Sophie Marmol developed malaria while in the Gambia: "I had blood tests there, and then came back and was sick. I had further tests and they found I had malaria. I had treatment with quinine and I was kept in for five days," she says.
"My mistake was that I stopped taking my antimalaria drugs. If I hadn't stopped I wouldn't have got malaria, it's as simple as that. I stopped because I was getting diarrhoea, but after my experience my advice to everyone is to take anti- malaria drugs."
According to the Hospital for Tropical Diseases, one of the problems is that reports about side-effects of antimalaria drugs have confused and alarmed people.
"Cases of malaria occurring over the Christmas holidays make it clear that some travellers are not getting balanced, clearly presented information about anti- malaria drugs," they say in their BMJ report.
But there is also a gung-ho attitude to taking antimalaria drugs, according to Dr Steve Gillespie, reader in microbiology at the Royal Free Hospital, London.
"Lots of people go off on safari, they all meet up in the bar and the Australians, the Brits and the Americans all find that they are taking different medication. Then they come to the conclusion that doctors don't know what they are talking about, they stop taking the drug, and then they die.
"People must be aware that malaria can kill. I would never dream of not taking antimalaria drugs," he says.
Apart from side-effects, another complication for doctors trying to get the message across is that antimalaria drugs are not 100 per cent effective, although mefloquine does give 90 per cent protection in some areas, particularly sub- Saharan Africa.
Andy Ramsay, 37, caught malaria in Tanzania, despite taking antimalaria drugs: "I was taking my medication but sometimes it does break through. You get a headache and flu-like symptoms. I was given quinine, which was not very pleasant. Although I did get malaria, people must tackle their anti- malaria drugs. There are side-effects, but people dying from side- effects are a lot less rare than people dying of malaria," he says.
A further complication is that travellers can get confused.
"Each country has a different malaria requirement, so it gets very complicated. Malaria areas are most of sub-Saharan Africa and many parts of South America. South-east Asia is very variable, from none in most of Thailand to a lot in Burma and rural Cambodia," says Dr Behrens.
"People need to be properly educated and it's not just about taking tablets, but starts with bite avoidance. Everybody should get full professional advice on all related issues of malaria avoidance."
Dr Anthony Bryceson, consultant physician at the Hospital for Tropical Diseases, says that anyone who returns from holidays in malaria areas this Christmas and has flu-like symptoms should see their doctor.
"Death is usually due to people not thinking about it because flu-like symptoms are common at this time of year," he says.
The safest holiday destinations this Christmas are the coldest. But there are dangers even here. While almost all malaria is caught overseas, the increase in long-haul travel has led to cases in Europe of "baggage malaria", where mosquitoes have survived in airliners long enough to bite and infect victims who just happen to be passing through the airport.