Mosquitos transmit the malaria parasite between hosts. A vaccine that works by administering chemically weakened parasite cells. PHILIPPE HUGUEN/AFP/Getty Images

A four-year-old girl has died in Italy after she mysteriously contracted malaria, almost 40 years after the country was declared free of the disease.

The girl, from Trentino in the north of the country close to the Swiss-Austria border, had not been abroad and doctors are unsure how she contracted the condition.

She had initially been treated at a hospital in her hometown but after concerns were raised when she lost consciousness, she was transferred to Brescia's Civil Hospital who specialise in tropical diseases.

A full investigation has been launched to find out how the girl managed to contract the deadly disease, despite the fact that she had never left the country in her life.

There have been thousands of cases of malaria in Italy over the past few years, but almost all of these have been in people who have travelled abroad to countries at risk of the condition.

In December, Italy's health ministry revealed that of the 3,500 cases between 2011 and 2016, all bar seven had been imported from another country.

Despite these numbers, Italy has been free of malaria as an indigenous disease to the country since 1970, however health officials in recent years have warned that the effects of climate change may increase these numbers.

Warmer temperatures have attracted new species of insects, particularly the Asian Tiger mosquito, which is known to regularly transmit the disease.