A debilitating tropical virus carried by mosquitoes has become established in Europe for the first time.
The Ministry of Health in Italy has confirmed about 160 cases of chikungunya in the Ravenna region in northern Italy.
Travellers have been advised to protect themselves against mosquito bites.
The European Centre for Disease Control urged pregnant women and those with chronic illnesses to seek medical advice before visiting the area.
The villages of Castiglione di Ravenna and Castiglione di Cervia have reported most of the cases.
The main symptoms of the patients were high fever and joint pain, as well as headache, muscle pain, rash and less frequently gastrointestinal symptoms.
One death was reported in a 83-year old individual with underlying medical conditions.
Professor Antoine Flahault, who coordinates French research on chikungunya, said the Italian outbreak was a "world first" outside the tropics.
Writing in the Quotidien du Medecin journal, he said the extension of the virus beyond its Indian Ocean origins was "worrying without being alarming".
He suggested that the very high density of mosquitoes in and around Ravenna had fuelled the outbreak.
"The mosquito vectors (carriers) of this disease have been in Italy for several years. All we know is that increased temperatures and humidity make the climate more tropical and favour the proliferation of mosquitoes," he said.
The virologist said the situation in Ravenna was under control and measures had been taken to reduce the number of mosquitoes.
Chikungunya gets its name from a Swahili word meaning "that which bends up" because of the arthritic-type symptoms that leave victims stooped.
Symptoms usually appear between four to seven days after being bitten and can persist for several weeks.
There is no vaccine against chikungunya.