Speaking to reporters during a visit to Madeira to assess the outbreak, Leal da Costa lauded the island's dengue detection and treatment system, saying dengue-carrying mosquitoes had apparently been brought inadvertently from a tropical country earlier this year.

"With this imported Aedes aegypti mosquito we've had the cases of the illness in humans, but it is diminishing and is being treated in exemplary fashion," he said in televised comments.

He warned, however, that the complete eradication of the mosquito on the island, which is popular with tourists, "will be very difficult since it has found a habitat here".

Dengue fever is a mostly tropical viral infection producing symptoms that can range from mild flu-like illness to potentially deadly forms which develop in around 5 percent of patients. It is sometimes known as "breakbone fever" because of the severe pain it can cause.

On December 5, the health ministry said in its latest weekly report that 1,993 cases of dengue had been reported since the start of the outbreak, with a 54 percent drop in the number of cases registered in the week of November26-December2 from the preceding week and that all those infected were recovering.

A total of 118 people have received hospital treatment in Madeira since October, but there have been no deaths.

The ministry said 42 cases of the disease had been found in Britain, Germany, Sweden and France among travelers returning from Madeira.

(Reporting by Andrei Khalip; editing by Axel Bugge and Andrew Roche)

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