New figures from the Health Protection Surveillance Centre (HPSC) have revealed that malaria cases here have risen by over 100% in the first six months of 2006, with 42 cases reported. Just 19 cases were reported in the same period last year.

"There is a very limited number of explanations as to why this is happening, " said Dr Simon Collins of the Tropical Medicine Bureau in Dublin.

"Because more and more people are travelling to countries where malaria is present, higher numbers are becoming infected. But it is also a fact that people aren't getting enough advice on how to prevent malaria and aren't taking the medication."

Malaria is spread among humans by the bite of a malaria-infected mosquito, and if not treated properly can be fatal. Christopher Gallagher (24) from Derry died last May after contracting the disease in northern Thailand.

Ninety per cent of malaria cases occur in Africa, but the disease is also present in parts of Central and South America and South-east Asia, which is currently a very popular destination for Irish tourists.

A survey carried out in Dublin Airport last year revealed that 22% of travellers did not see the need to take preventative medication when there was nothing wrong with them.

Certain anti-malarial tablets have also gained a bad reputation in recent years for their strong side-effects.

"People have got very nervous about the side-effects of anti-malarial tablets, but that's only part of the truth, " said Collins, who has worked with malaria patients in Africa.

"One tablet [Lariam] can badly affect one in five patients, but there are a couple of very good tablets with minimal side effects. People need to talk to their doctor at length about what is best for them."

Malaria is not the only disease that Irish people are picking up abroad. In the past two years, there have been three reported cases of West Nile Virus, another mosquito-borne disease. No other northern Europe country has ever reported any cases.

According to Dr Jeff Connell of the National Virus Research Laboratory (NVRL) in UCD, they have tested for 20 cases of dengue fever in the last two years and believe many more cases are going undiagnosed.

Dengue fever is another mosquitoborne disease found in malaria areas that can only be prevented through the use of mosquito repellents. It causes severe headaches, joint pain and, in some cases, long-term depression.

"We would recommend that anyone coming home from these areas who is suffering from severe headaches, pain around the eyes and maybe a rash should get tested, " said Connell.