“At one point, I simply couldn’t stand up to get out of the car,” said Antonio Ciano, 62, an elegant retiree in a pashmina scarf and trendy blue glasses. “I fell. I thought, OK, my time is up. I’m going to die. It was really that dramatic.”

By midmonth, more than 100 people had come down with the same malady. Although the worst symptoms dissipated after a couple of weeks, no doctor could figure out what was wrong.

People blamed pollution in the river. They denounced the government. But most of all they blamed recent immigrants from tropical Africa for bringing the pestilence to their sleepy settlement of pastel stucco homes.

“Why immigrants?” asked Rina Ventura, who owns a shop selling shoes and purses. “I kept thinking of these terrible diseases that you see on TV, like malaria. We were terrified. There was no name and no treatment.”

Oddly, the villagers were both right and wrong. After a month of investigation, Italian public health officials discovered that the people of Castiglione di Cervia were, in fact, suffering from a tropical disease, chikungunya, a relative of dengue fever normally found in the Indian Ocean region. But the immigrants spreading the disease were not humans but insects: tiger mosquitoes, who can thrive in a warming Europe.

Aided by global warming and globalisation, Castiglione di Cervia has the dubious distinction of playing host to the first outbreak in modern Europe of a disease that had previously been seen only in the tropics.

“By the time we got back the name and surname of the virus, our outbreak was over,” said Rafaella Angelini, director of the regional public health department in Ravenna.

The epidemic proved that tropical viruses are now able to spread in new areas, far north of their previous range. The tiger mosquito, which first arrived in Ravenna three years ago, is thriving across southern Europe and even in France and Switzerland.

“This is the first case of an epidemic of a tropical disease in a developed, European country,” said Roberto Bertollini, director of the World Health Organisation’s Health and Environment programme. “Climate change creates conditions that make it easier for this mosquito to survive and it opens the door to diseases that didn’t exist here previously. This is a real issue. Now, today. It is not something a crazy environmentalist is warning about.”

Was he shocked to discover chikungunya in Italy, his native land? “We knew this would happen sooner or later,” he said. “We just didn’t know where or when.”

It certainly caught this town off guard on August 9, when public health officials in Ravenna received an angry call from Stefano Merlo, who owns the gas station.

August is not the season for high fevers, Angelini agreed, and within days of interviewing patients she was intrigued.

Hard-working shopkeepers could not get out of bed because their hips hurt so much. Able-bodied men could not lift spoons to their mouths. (Months later, many still have debilitating joint pain.)

From the start, doctors suspected that the disease was spread by insects, rather than people. While almost all homes had one person who was ill, family members seemed not to catch the disease from one another.

But the biggest mystery is whether chikungunya will emerge here next summer. In the tropics, it is a year-round disease, since the mosquitoes breed continually. But the virus can winter over in mosquito eggs, too, and no one knows if there are reservoirs of sleeping eggs in some pool of water in Italy.

With climate change at hand, Bertollini said, chikungunya will surely be back somewhere in Europe again.