Dengue fever detected in Spaniards who have never been in the tropics

A tropical disease passed on by mosquitoes, dengue causes high fever, general body aches and pains, and vomiting.

There is no vaccine, and anyone who travels to rural areas in the tropics is normally advised to use strong fly repellent with DEET as one of its ingredients.

The confirmed cases are two Spaniards from the same family who live in Alhama (Murcia) and are said to be in their 50s or early 60s.

Neither had ever travelled to a high-risk area, and it is believed the disease may have been passed on by the so-called 'tiger mosquito', which has a sting that causes much greater irritation than 'mainstream' mosquitoes.

A third case, within the same family, has not been confirmed, but the patient is around the same age and has not travelled outside of Spain recently.

All three were in Cádiz when they contracted the infection.

Spanish health authorities say the two definite dengue cases are a man and a woman who live together in Alhama, but are not partners, and that the third possible patient lives in Madrid.

In each case, tropical disease experts have confirmed the infection was caught in Spain, which has never happened before.

They suspect other cases may have gone undetected in the past, since sometimes a dengue infection does not present any symptoms.

Dengue cannot be transmitted between humans, but is caused by the 'flavivirus', of which tiger mosquitoes and other mosquitoes found in the tropics are carriers.

Generally, it is not life-threatening, but is extremely unpleasant.

Government health sources say a case of dengue in a patient who has not travelled to the tropics could have been transmitted in one of two ways – either a carrier mosquito became trapped on a plane or ship, or an 'ordinary' mosquito may have bitten someone already infected and then stung the people currently in hospital.

The only insect in Spain able to transmit the virus is the Aedes Albopictus, or 'tiger mosquito', which were first found in the country about five years ago and are mainly concentrated on the Mediterranean.

In parts of neighbouring countries, such as France and Italy, with a tiger mosquito presence, sporadic cases of dengue or even Chikungunya – transmitted by the Aedes Aegypti mosquito which also carries malaria and Zika – have been confirmed in the last few years.

Health authorities in Spain say local councils and regional governments take stringent measures to combat tiger mosquitoes, which are most prevalent in summer.

Tropical disease experts say it is 'no surprise' to find dengue cases in Spain, but that they are likely to be rare and isolated and there is no major risk to the population.

Damp areas, rural parts and anywhere near water are the most likely to house tiger mosquito nests, but only during warm periods.

Anyone likely to visit these areas should use a strong insect repellent.