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Malaria travels back to Europe

Researchers test insecticides in the garden of the Swiss Tropical Institute, Basel, in 1958 (STI)

It is less than 30 years since endemic malaria was finally eradicated in western Europe.

However 12,000 cases are imported every year, brought back by travellers from tropical countries. These result in about 60 deaths annually.

Drainage, drugs and insecticide contributed to malaria's disappearance along with improved sanitation, nutrition and living conditions.

In the last major outbreak in the Netherlands in 1946 nearly 2,400 people were infected in the town of Zaandam.

Southern Europe remained in the grip of seasonal epidemics until the 1950s when DDT spraying helped bring it under control.

It was not until 1975 that the last pocket of indigenous malaria in Greek Macedonia was considered eliminated and the World Health Organization declared the continent free of the disease.

Hitching a ride

In the early 19th century, malaria occurred in Switzerland in the river valleys of the Rhine, Limmat and Reuss and near Lakes Zurich and Lucerne.

Better drainage and improved river maintenance gradually reduced breeding places for mosquitoes.

"Through the famous drainages that were undertaken in the 19th century, we basically got rid of malaria," said Marcel Tanner, director of the Swiss Tropical Institute.

By the second half of the century, pockets of the disease were confined to the Neuchâtel valley and the cantons of Ticino, Vaud and Valais along the Rhone, mainly between Sion and Geneva.

Numerous imported cases were seen in Switzerland during the Second World War in refugees from Italy and eastern Europe.

Then, in 1970, two military recruits who were stationed near Zurich airport contracted malaria though they had never visited any endemic countries.

It is believed that a few infected anopheles mosquitoes were carried to Switzerland from Africa inside an aircraft.

Other cases of airport malaria have been reported around Europe, including two more from the Zurich area.

In 1999, Switzerland witnessed its first case of malaria transmitted though a blood transfusion when a 70-year-old hospital patient died two weeks after an operation.

Full circle

Anopheles mosquitoes - the vectors of malaria - still exist in Switzerland but experts say the return of endemic malaria is unlikely today.

"If you had an extremely warm summer and a high number of anopheles biting about 50 to 100 infected people in the same place and favourable temperature conditions to complete the cycle, this could lead to transmission," said Tanner.

"This is the situation we had during the Second World War when troops from southern Italy, carrying the parasite, were concentrated in one camp. You had anopheles around the camp and the summers of 1944 and 1945 were very warm.

"The malaria parasite needs a certain optimal temperature to develop in the mosquito. If you don't get the temperature, the mosquitoes die before the cycle is complete.

Fatal mistake

Every year since 1988, about 300 people have acquired malaria abroad and brought it back to Switzerland, resulting in a handful of deaths.

The figures represent a tiny fraction of the two million annual departures from Switzerland to tropical countries.

Tanner said imported malaria was understandable given the huge rise in international travel but that the fatalities could be avoided.

"People coming down with malaria think it's flu or they consult a doctor but fail to mention that they have travelled to tropical areas," he said. "In both cases, diagnosis is delayed and it can lead to a life-threatening condition."

Avoiding mosquito bites remains the key to successful prevention said Tanner. He added that it was also essential for travellers to continue taking prophylactic drugs upon their return.

swissinfo, Vincent Landon

In brief

Malaria is a life-threatening parasitic disease transmitted by mosquitoes.

It was once thought to come from fetid marshes - hence the name mal aria (bad air).

In 1880, scientists discovered the real cause - a one-cell parasite called plasmodium.

It is spread by the bite of a female anopheles mosquito which needs blood to nurture her eggs.

During the mid 20th century, many countries with temperate climates eradicated the disease.

Today malaria is found throughout the tropical and sub-tropical regions of the world.

It causes more than 300 million acute illnesses and at least one million deaths annually.

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