Italy: Tropical disease affects the brain, 8 dead and dozens infected

The West Nile virus (WNV) is spreading in Italy and has led to an increase in the number of reported cases within a week. According to a July 31 report by the Italian health authority ISS, 57 new infections were registered within a week.

The West Nile virus, originally native to tropical regions, has also established itself in Europe due to climate change and is now considered endemic in Italy. It is transmitted by mosquitoes. The most severely affected regions are near the major cities of Rome and Naples, as well as in northern Italy, from Piedmont to Veneto.

Neurological complications occurred in 40 cases, or almost half of the registered infections. The virus attacks the brain and causes meningitis or encephalitis, i.e., inflammation of the brain and meninges. According to the report, the mortality rate for these neuroinvasive forms was 20 percent. This is six percent higher than last year, when Italy also battled a major outbreak of West Nile virus .

The news agency Ansa reports a ninth death. A 76-year-old man died in a hospital in Grazzanise, a municipality near Naples.

• Worldwide distribution: West Nile virus (WNV) is widespread on all continents and is transmitted seasonally in Southern Europe. Countries such as Italy, Greece, and France, as well as parts of the Balkans and Turkey, are particularly affected.
• Transmission routes: Transmission occurs primarily through mosquitoes, which transmit the virus from infected birds to humans and other mammals. Other possible routes of infection include organ transplants, blood transfusions, and pregnancy.
• Course of the disease: Most infections are asymptomatic. About 20 percent of those affected develop flu-like symptoms, while only about one percent become seriously ill, usually with a neuroinvasive disease such as meningitis or encephalitis.
• Diagnosis: Detection is performed via RT-PCR in the first few days, followed later by antibody tests. Due to possible cross-reactions with other flaviviruses, confirmation by plaque reduction neutralization testing (PRNT) or sequencing is necessary.
• Blood donation risk: WNV can be transmitted through non-virus-inactivated blood products. In affected regions, blood donors must either take a 28-day break or be tested for WNV RNA to ensure the safety of blood products. According to the report, two people in Italy were also infected while donating blood in 2025.

According to a bulletin from the Robert Koch Institute (RKI), the 2025 season for mosquito-borne pathogens has also begun in Germany. West Nile virus has been detected in Germany since 2019, with recent increases in infection rates (26 cases in 2024). What's worrying is that, according to the Robert Koch Institute (RKI), the pathogen can also overwinter in more northern regions, which is why the agency expects further spread.