Human neuroinvasive Toscana virus infections in Italy from 2016 to 2023. Increased incidence in 2022 and 2023

Background: Toscana virus (TOSV) is transmitted to humans through bites of infected sand flies. Neuroinvasive TOSV infections are leading causes of meningitis/encephalitis in southern Europe and notifiable in Italy since 2016. In 2022-23, Italy experienced extreme climate anomalies and a concomitant increase in mosquito and tick-borne disease transmission.AimTo identify the spatiotemporal distribution and risk groups of neuroinvasive TOSV infections in Italy in 2022-23 vs 2016-21.MethodsWe retrospectively described all autochthonous, laboratory-confirmed neuroinvasive TOSV cases notified to the national surveillance system in 2016-23 using frequencies, proportions, incidences and incidence risk ratios (IRRs) with 95% CIs, stratified by year, sex, age, region/autonomous province (AP) of infection/exposure and infection/exposure municipality by urbanisation level.ResultsIn 2022-23, 276 cases were notified (average annual incidence: 2.34/1,000,000 population) vs 331 cases in 2016-21 (0.92/1,000,000), with increased incidence extending into September. In 2022-23, infections were acquired in 12/21 regions/APs, predominantly in Emilia Romagna (57.6%; 159/276) as in 2016-21, including four regions/APs with no local infections in 2016-21. Similar to 2016-21, during 2022-23 residence in rural municipalities (vs urban), male sex, working age (19-67 years) and age > 67 years (vs ≤ 18 years) were identified as risk factors with IRRs of 2.89 (95% CI: 2.01-4.17), 2.17 (95% CI: 1.66-2.84), 5.31 (95% CI: 2.81-10.0) and 5.06 (95% CI: 2.59-9.86), respectively.ConclusionItaly experienced a nearly 2.6-fold increase in neuroinvasive TOSV incidence in 2022-23 vs 2016-21. Raising public awareness on risk factors and personal protection measures may enhance prevention efforts.