Doctors in Italy are shocked by the recent death of 4-year-old Sonia Zago from malaria.
Though there were 212 million cases of malaria globally in 2015, according to the World Health Organization, Europe was declared malaria-free that same year.
Zago was admitted to the hospital on Saturday in Trento, Italy with a high fever, according to Italian newspaper Corriere della Sera. She fell into a coma and was diagnosed with cerebral malaria, which can cause brain damage and is among the most fatal forms of malaria, according to the Mayo Clinic.
The young girl was transferred to a neighboring hospital that specializes in tropical diseases for treatment, but died on Monday morning.
Zago had never traveled abroad and the Anopheles mosquito that can transmit malaria is not known to live in Italy, according to NPR. So doctors are at a loss trying to determine how Zago became infected.
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"It's a mystery, almost impossible," Paolo Bordon, general manager of the provincial health service, told Corriere della Sera.
Italy has been malaria-free since the 1950s, NBC News reports, and was officially declared malaria-free by the WHO in 1970. While there have been some cases of malaria in the country since, they have primarily been cases of tourists infected abroad in countries where malaria remains common.
"This is the first time in 30 years of career that I have been involved in a case of native malaria in Trentino," an infectious disease specialist at Trento's Santa Chiara Hospital told Corriere della Sera.
According to UNICEF, 90% of malaria cases worldwide occur in Sub-Saharan Africa, killing more than 1 million people each year, most of whom are children under the age of five.
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Malaria is difficult to eradicate, but preventable. The disease was endemic in Italy through the first half of the 20th century because of the country’s coastal and marshy areas, which attract mosquitos, according to NPR. However, a campaign launched in 1947 managed to successfully eradicate malaria in Italy, primarily through the use of pesticides.
Italy’s Ministry of Health has dispatched a team of experts to investigate, and officials are considering the possibility that an infected insect was brought into the country by a traveler, according to NPR.
Doctors are also considering the possibility, though highly improbable, that Zago was infected when she shared a treatment ward with two children who had contracted malaria in Burkina Faso, while she was seeing treatment for diabetes, according to the BBC.