First Human Usutu Virus Reported in Asti (Piedmont, Italy, August 2022) and Early Follow-Up

The recent emergence of West Nile virus (WNV) and Usutu virus (USUV) in some European countries has triggered an increase in animal and human cases across Europe. Wild birds, serving as key reservoirs for WNV and USUV, often act as crucial indicators for the introduction and spread of these viruses. Currently, there is no durable large‐scale monitoring for WNV in Belgium, and specific monitoring for USUV is lacking. In Flanders, passive WNV monitoring in birds has been in place for many years, while initial efforts to initiate active monitoring started in 2022. Here, we present the results of a limited study conducted during the vector seasons of 2022 and 2023 in Flemish bird populations to actively and passively monitor the prevalence of WNV and additionally assess the presence of USUV. Several real‐time reverse transcription‐PCR tests were employed for virus detection, revealing the absence of WNV‐RNA during both vector seasons. Conversely, USUV‐RNA was identified in 2022 through active surveillance, affecting two (5.5%) out of 36 birds (Corvus corone), and in passive surveillance, impacting eight (72.7%) out of 11 birds (Turdus merula [6] and Rhea pennata [2]). In 2023, active surveillance was more extensive and identified 16 (7.2%) USUV‐RNA positive birds (Buteo buteo [1], T. merula [14] and Athene noctua [1]) out of 222 examined birds, while passive surveillance detected two (7.1%) positive birds (T. merula [1], and Larus marinus [1]) out of 28. Viral sequence information was obtained from seven USUV‐positive birds using whole genome sequencing or Sanger sequencing. Phylogenetic analysis placed all identified strains within the Africa 3 lineage. This restricted WVN monitoring effort in Flanders did not reveal WNV presence, but found indications of an endemic USUV circulation in Belgium. It is crucial to intensify monitoring efforts for WNV in the coming years, considering its endemic status in several European countries and its expanding geographical range in northern Europe.

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The Re-Emergence of Neuroinvasive Flaviviruses in Croatia During the 2022 Transmission Season

Bogdanic,

Savic,

Klobucar

et al. 2024

Microorganisms

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(Re-)emerging arboviruses, such as tick-borne encephalitis virus (TBEV), West Nile virus (WNV), and Usutu virus (USUV), are continuously increasing in incidence. We analyzed the epidemiological characteristics of flavivirus infections in humans, sentinel animals, and mosquitoes detected in the 2022 transmission season in Croatia. From April to November 2022, 110 hospitalized patients with neuroinvasive diseases (NID) were tested for the presence of arboviruses. RT-qPCR was used to detect TBEV, WNV, and USUV RNA. An ELISA and virus neutralization tests were used for the detection of flavivirus antibodies. TBEV infection was confirmed in 22 patients with NID. WNV NID was detected in six patients. TBE showed male predominance (81.8%; male-to-female ratio of 4.5:1). All but one WNV patients were males. TBE occurred from April to August, with the majority of patients (83.3%) being detected during the May–June–July period. WNV infections were recorded in August and September. In addition to human cases, asymptomatic WNV infections (IgM positive) were reported in 10 horses. For the first time in Croatia, WNV NID was observed in one horse that presented with neurological symptoms. Furthermore, USUV was confirmed in one dead blackbird that presented with neurological symptoms. A total of 1984 mosquitoes were collected in the City of Zagreb. Two Ae. albopictus pools tested positive for flavivirus RNA: one collected in July (USUV) and the other collected in August (WNV). A phylogenetic analysis of detected human and avian strains confirmed WNV lineage 2 and the USUV Europe 2 lineage. The presented results confirm the endemic presence of neuroinvasive flaviviruses in continental Croatia. The continuous monitoring of virus circulation in humans, sentinel animals, and mosquitoes is needed to reduce the disease burden.

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First Human Usutu Virus Reported in Asti (Piedmont, Italy, August 2022) and Early Follow-Up

Cited by 3 publications

References 18 publications

Usutu virus avian and human infection after more than 25 years of circulation

Usutu virus avian and human infection after more than 25 years of circulation

West Nile Virus Monitoring in Flanders (Belgium) During 2022–2023 Reveals Endemic Usutu Virus Circulation in Birds

The Re-Emergence of Neuroinvasive Flaviviruses in Croatia During the 2022 Transmission Season

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