Britons travelling to exotic locations are being warned of the risks of contracting potentially fatal malaria by health experts.
Malaria is carried by mosquitoes
The number of travellers to malarial areas has soared by around 150% over the last decade.
But people are not taking anti-malaria tablets, putting themselves at risk, the Health Protection Agency said.
Last year, three people died after 26 travellers to The Gambia contracted the most serious type of the condition.
The HPA is warning that nine out of 10 Britons who contract malaria are carrying this form of the disease - plasmodium falciparum.
Latest figures show that of the 1,722 Britons with malaria in 2003, 1,339 had plasmodium falciparum - 78% of cases, up from 17% if cases in 1977.
That year saw 16 people die from malaria, up from nine the year before.
The increasing trend of taking a break in a far-flung destination or heading of for a last-minute holiday is leading to people not thinking about malaria tablets, or forgetting to complete the whole course, the HPA said.
Travel to India has more than doubled over the last decade, and more holidaymakers are heading for destinations such as Cambodia, Thailand, the Middle East and Vietnam, according to the Association of British Travel Agents.
An HPA spokeswoman said: "It's not so much complacency, it's people thinking they won't need malaria tablets for what they see as a normal holiday.
"The indication is that, the number of cases is decreasing but the fatality rate is increasing.
"The message would be that, with the number of people being killed, it is so important to remember to take the treatment prescribed by the doctors."
She added: "A lot of people forget once they come back that they need to continue to go through the whole dose.
"In addition, people visiting friends and family who may originate from an area where malaria is present may wrongly think they are immune."
Travellers visiting malarial areas are being advised to visit their doctor or travel clinic before they go abroad to get advice on the best anti-malarial measures.
Once abroad they should use insect repellent, keep arms feet and legs covered and sleep under mosquito netting if outside.
Early signs of malarial infection include fever, a flu-like illness, shaking, muscle ache and tiredness.