The European Centre for Disease Prevention and Control (ECDC.L) which monitors disease in the European Union, said the outbreak was "significant but not entirely unexpected" given that the most efficient carriers of the disease, mosquitoes known as Aedes aegypti, have an established presence in Madeira.

"Portuguese public health authorities are implementing control measures to reduce the risk of sustained transmission locally, the export of infected vectors from the island, and to minimise the impact on the affected population," it said.

The first local transmissions of dengue fever in Europe were recorded in France and Croatia in 2010.

Earlier this year, Greek health officials attributed the death of an 80-year-old man to its first case of dengue since an outbreak there in 1927-28.

The ECDC said the risk for tourists visiting Madeira and for residents of the island would "depend on the course of the outbreak in the coming weeks and the effectiveness of the control measures."

It did not recommend any restrictions on travel or tourism to Madeira, but advised people to protect themselves adequately against mosquito bites, particularly during the day which is when dengue-carrying mosquitoes are most active.

Jane Jones, a travel-associated infection expert at the Britain's Health Protection Agency HPA.L, stressed that dengue fever cannot be passed from person to person and infection can only occur after being bitten by a mosquito carrying the virus.

"To minimise the risk of being bitten it is advisable to wear appropriate clothing to cover up - such as long sleeve tops and trousers, and to use insect repellents," she said in a statement.

In the past 50 years there has been a thirty-fold jump in dengue cases worldwide as the disease has thrived in the mega-cities of the tropics and been spread by globalisation.

The disease is a viral infection that can cause a range of symptoms, from mild flu-like illness to more serious illnesses including rashes and bone pain. Severe and potentially deadly forms develop in around 5 percent of patients.

The World Health Organisation officially puts dengue infections at between 50 million and 100 million a year, though many experts think this assessment from the 1990s is a significant under-estimate. It is estimated to kill about 20,000 people a year, and the majority of cases are in South-East Asia and the Western Pacific.

The ECDC advised authorities in geographical areas neighbouring Madeira, such as the Canary Islands, as well as other EU member states to consider stepping up surveillance of Aedes mosquito populations to assess their risk of seeing dengue fever spread. (Additional reporting by Ben Hirschler; Editing by Jon Hemming)

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