Association of avian #biodiversity and #WNV circulation in #Culex mosquitoes in Emilia-Romagna, #Italy

 

Abstract

Background

West Nile Virus (WNV) is a zoonotic arbovirus maintained in a transmission cycle between Culex mosquitoes and birds, occasionally spilling over into humans. The impact of avian biodiversity on WNV circulation remains debated, with studies reporting both negative and positive correlations (dilution and amplification effects respectively) across different settings. In Europe, this relationship remains largely unexplored, particularly in regions with high WNV transmission, such as Emilia-Romagna in Northern Italy.

Methods

We explored the association between avian biodiversity and WNV circulation in Culex mosquitoes in Emilia-Romagna using 11 years (2013–2023) of entomological surveillance data paired with two avian data sources. We calculated avian biodiversity indices (Shannon’s, Simpson’s, and Chao2) from observation records from the Farmland Bird Index project and applied linear regression models to assess their relationship with WNV detection frequency. Moreover, we used Bayesian spatiotemporal regression models and gridded weekly avian abundance estimates from the eBird project to analyse the associations between avian species richness indices and WNV transmission risk quantified by vector index (VI) at 68 geolocated mosquito traps across the region.

Results

We observed consistent negative associations between WNV detection frequency in the Culex population and avian biodiversity indices, supporting the dilution effect hypothesis (DEH). We found that non-passerine species richness was negatively associated with VI while passerine species richness showed a positive association after adjusting for covariates and spatial random effects. These findings suggest that passerines may amplify WNV transmission, whereas the presence of non-passerine species is associated with reductions in WNV circulation.

Significance

This study provides the first empirical evidence supporting the DEH for WNV in Europe. These findings have important implications for biodiversity conservation and integrated public health surveillance activities across Europe.

Source: 

Link: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014076

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#Italy, #WNV & #USUV Integrated #Surveillance - Weekly Bulletin No. 16 - 30 October 2025 (Summary)

 

{Summary}

-- During current epidemiological week (from 23 to 29 Oct. 2025), two new human cases of infection with West Nile Virus have been reported. 

-- The cumulative number of confirmed cases this season so far rose to 773 (they were 771 last week), of these: 

- 367 were West Nile Neuroinvasive Disease (WNND): 17 in Piedmont, 56 Lombardy, 35 Veneto, 4 Friuli-Venezia Giulia, 1 Liguria, 30 Emilia-Romagna, 11 Tuscany, 1 Marche, 87 Latium, 2 Molise, 83 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 3 Sicily, 28 Sardinia, 

- 56 were asymptomatic cases detected in blood donors, 

- 339 were West Nile Fever cases (of which: 1 imported from Kenya, 1  from Egypt and 1 from Maldives), 

- 3 asymptomatic cases, 

- 8 unspecified cases. 

-- Among confirmed cases, 72 fatalities have been recorded: 7 in Piedmont, 9 Lombardy, 1 Veneto, 2 Emilia-Romagna, 1 Marche, 19 Latium, 29 Campania, 2 Calabria, 1 Sicily, 1 Sardinia. 

- The Case-Fatality Rate in WNND cases is 19.6% (it was 20% in 2018, 14% in 2024). 

-- Since the start of the epidemic season, 11 confirmed human cases of Usutu virus infection were reported: 2 in Piedmont, 3 Lombardy, 2 Veneto, 1 Tuscany, 3 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_16.pdf

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#Italy, #WNV & #USUV Integrated #Surveillance - Weekly Bulletin No. 14, 15 Ocotber 2025 (ISS, edited)

 

{Summary}

-- New human cases of West Nile Virus infection continue to be reported albeit with reduced intensity. 

-- During current epidemiological week (from 9 to 15 October 2025) 26 new confirmed cases have been reported. 

-- The total number of cases so far is 767 (they were 740 last week), of these: 

- 366 were West Nile Neuroinvasive Disease (WNND): 17 in Piedmont, 56 Lombardy, 34 Veneto, 4 Friuli-Venezia Giulia, 1 Liguria, 32 Emilia-Romagna, 10 Tuscany, 1 Marche, 86 Latium, 2 Molise, 83 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 3 Sicily, 28 Sardinia, 

- 57 were asymptomatic cases among blood donors, 

- 333 were West Nile Fever cases (of which 1 imported from Kenya, 1 from Egypt and 1 from Maldive), 

- 3 asymptomatic cases, 

- eight unspecified cases. 

-- Among confirmed cases, 69 fatalities have been reported: 7 in Piedmont, 9 Lombardy, 2 Emilia-Romagna, 18 Latium, 29 Campania, 2 Calabria, 1 Sicily, 1 Sardinia. 

-- The case-fatality rate in WNND cases stands at 18.8% (in 2018 it was 20%, in 2024 it was 14%). 

-- So far this season, 10 cases of Usutu virus infection have been recorded: 2 in Piedmont, 3 Lombardy, 2 Veneto, 3 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_14.pdf

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#Italy, Integrated #WNV & #USUV #Surveillance - Weekly Bulletin No. 13, 9 October 2025 (Summary): 22 new confirmed cases

{Summary}

-- During current epidemiological week, a rise in the West Nile Virus human cases has been observed although with reduced intensity compared most recent weeks. 

-- Twenty-two new confirmed human cases have been reported during surveillance week from 2 to 8 October 2025. 

-- The cumulative number of cases rose to 740 (they were 718 last week), of these: 

- 354 were West Nile Neuroinvasive Disease (WNND): 16 in Piedmont, 53 Lombardy, 33 Veneto, 4 Friuli-Venezia Giulia, 1 Liguria, 30 Emilia-Romagna, 11 Tuscany, 1 Marche, 84 Latium, 2 Molise, 81 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 3 Sicily, 26 Sardinia,

- 57 were asymptomatic cases in blood donors, 

- 318 were West Nile Fever cases, of which 1 imported from Kenya, 1 from Egypt and 1 from Maldives, 

- 4 asymptomatic cases, 

- 7 unspecified cases. 

-- Among confirmed cases there were 68 fatalities: 7 in Piedmont, 9 Lombardy, 2 Emilia-Romagna, 18 Latium, 28 Campania, 2 Calabria, 1 Sicily, 1 Sardinia. 

- The Case-Fatality Rate in WNND cases is now at 19.2% (it was 20% in 2018 and 14% in 2024). 

-- During current epidemic season, ten Usutu Virus human cases have been confirmed: 2 in Piedmont, 3 Lombardy, 2 Veneto, 3 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_13.pdf

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#Italy, Integrated #WNV & #USUV #Surveillance - Weekly Bulletin No. 12, 2 October 2025: 38 new confirmed cases (Summary)

 

{Summary}

-- During current epidemiological week (from 25 September to 1rst October 2025), 38 new confirmed human infection with West Nile Virus have been reported. 

-- Since the beginning of the epidemic season, 718 confirmed cases have been recorded in Italy (they were 680 in the last bulletin), of these: 

- 341 were West Nile Neuroinvasive Disease (WNND): 15 in Piedmont, 51 Lombardy, 30 Veneto, 4 Friuli-Venezia Giulia, 1 Liguria, 27 Emilia-Romagna, 11 Tuscany, 1 Marche, 84 Latium, 2 Molise, 79 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 2 Sicily, 25 Sardinia, 

- 57 were asymptomatic cases in blood donors, 

- 309 were West Nile Fever cases (1 imported from Kenya, 1 Egypt, and one Maldives), 

- 4 asymptomatic cases, 

- 7 unspecified cases. 

-- Among confirmed cases, there have been 49 fatalities: 7 in Piedmont, 5 Lombardy, 2 Emilia-Romagna, 18 Latium, 14 Campania, 2 Calabria, 1 Sardinia. 

- The Case-Fatality Rate in WNND cases was 14.4% (it was 20% in 2018 and 14% in 2024. 

-- This season 10 confirmed Usutu virus human infections have been recorded: 2 in Piedmont, 3 Lombardy, 2 Veneto, 3 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_12.pdf

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#Italy, Integrated #WNV & #USUV #Surveillance - Weekly Bulletin No. 11, September 25 '25 (ISS, Summary)

 

{Summary}

-- During current surveillance week (from 18 to 24 Sept. '25), 33 new confirmed human cases of West Nile Virus have been detected. 

-- Since the beginning of the epidemic season, there have been 680 cases in total, (they were 647 last week); of these: 

- 321 were West Nile Neuroinvasive Disease (WNND): 15 in Piedmont, 44 Lombardy, 27 Veneto, 2 Friuli-Venezia Giulia, 1 Liguria, 25 Emilia-Romagna, 8 Tuscany, 1 Marche, 83 Latium, 2 Molise, 79 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 1 Sicily, 24 Sardinia), 

- 54 were asymptomatic cases in blood donors, 

- 296 were West Nile Fever cases (1 imported from Kenya, 1 Egypt and 1 Maldives), 

- 3 asymptomatic cases,  

- 6 unspecified cases. 

-- Among confirmed cases, there were 48 deaths: 7 in Piedmont, 5 Lombardy, 2 Emilia-Romagna, 17 Latium, 14 Campania, 2 Calabria, 1 Sardinia. 

- The Case-Fatality Rate among WNND cases was 14.9% (it was 20% in 2018 and 14% in 2024). 

-- During current surveillance week, nine new confirmed human cases of Usutu virus have been confirmed: 2 in Piedmont, 2 Lombardy, 2 Veneto, 3 Latium).

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_11.pdf

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#Italy, Integrated #Surveillance for #WNV & #USUV - Weekly Bulletin No. 10, 18 September '25 (Summary)

 

{Summary}

-- During current epidemiological week (11– 17 September 2025), 65 new confirmed human cases of infection with West Nile Virus have been reported. 

-- The total number of confirmed cases, since the beginning of the epidemic season, has thus risen to 647 (it was 582 last week), of these: 

- 300 were West Nile Neuroinvasive Disease (WNND): 15 in Piedmont, 39 Lombardy, 24 Veneto, 2 Friuli-Venezia Giulia, 1 Liguria, 23 Emilia-Romagna, 5 Tuscany, 83 Latium, 2 Molise, 77 Campania, 2 Apulia, 2 Basilicata, 5 Calabria, 1 Sicily, 19 Sardinia, 

- 54 were asymptomatic cases detected among blood donors, 

- 284 were West Nile Fever cases (one imported from Kenya), 

- 3 asymptomatic cases and 

- 6 unspecified casese. 

-- Among confirmed cases, there were 47 death cases: 7 in Piedmont, 5 Lombardy, 1 Emilia-Romagna, 16 Latium, 15 Campania, 2 Calabria, 1 Sardinia. 

- The Case-Fatality Rate in WNND cases was 15.8% (it was 20% in 2018 and  14% in 2024). 

-- This week nine confirmed cases of Usutu Virus infection have been reported: 2 in Piedmont, 2 Lombardy, 2 Veneto, 3 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_10.pdf

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#Italy, Integrated #Surveillance for #WNV & #USUV - Weekly Bulletin No. 9, 11 September '25 (summary): 80 new cases

{Summary}

-- During current epidemiological week (4 to 10 September), eighty new confirmed human cases of West Nile Virus infection have been reported in Italy.

-- Since the beginning of the epidemic season, there have been a total of 582 confirmed cases (they were 502 last week), of these: 

- 260 were West Nile Neuroinvasive Disease (WNND): 14 in Piedmont, 24 Lombardy, 22 Veneto, 1 Friuli-Venezia Giulia, 1 Liguria, 20 Emilia-Romagna, 3 Tuscany, 77 Latium, 2 Molise, 74 Campania, 1 Apulia, 2 Basilicata, 5 Calabria, 1 Sicily, 13 Sardinia, 

- 48 asymptomatic cases among blood donors, 

- 262 cases of West Nile Fever (1 imported from Kenya), 

- 4 asymptomatic cases, 

- 8 unspecified cases. 

-- A total of 39 fatal cases have been reported so far this season: 5 in Piedmont, 2 Lombardy, 1 Emilia-Romagna, 15 Latium, 14 Campania, 2 Calabria. 

- The Case-Fatality Rate among WNND cases is thus far at 15% (during 2018 season it was 20%, in 2024 14%). 

-- During current surveillance week there were 7 new confirmed Usutu Virus infection cases: 2 in Piedmont, 2 Lombardy, 1 Veneto, 2 Latium.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_09.pdf

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#Italy, Integrated #WNV & #USUV Viruses #Surveillance - Weekly #Bulletin No. 8, September 4 2025 (summary)

{Summary}

-- During current surveillance week (28 August - 3 September 2025): 

- 72 new confirmed human cases of West Nile Virus infection have been confirmed; 

-- The total number of cases since the beginning of epidemic season has risen to 502 (they were 430 in the last bulletin); of these: 

- 226 were West Nile Neuroinvasive Disease (WNND): 11 in Piedmont, 16 in Lombardy, 17 Veneto, 1 Friuli-Venezia Giulia, 1 Liguria, 15 Emilia-Romagna, 3 Tuscany, 71 Latium, 2 Molise, 72 Campania, 1 Apulia, 2 Basilicata, 5 Calabria, 1 Sicily, 8 Sardinia, 

- 40 were asymptomatic cases detected in blood donors, 

- 226 were West Nile Fever cases (one of them imported from Kenya),

- 5 asymptomatic cases, 

- 5 unspecified. 

-- So far there have been 33 fatal cases: 3 in Piedmont, 1 Lombardy, 1 Emilia-Romagna, 14 Latium, 12 Campania, 2 Calabria. 

- The Case-Fatality rate among WNND cases is thus far at 14.6% (in 2018 it was 20%, in 2024 14%). 

-- During current surveillance week, there have been 4 confirmed Usutu virus human infections: 2 in Piedmont, 1 Veneto, 1 Latium).

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_08.pdf

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#Italy, Integrated #WNV & #USUV #Surveillance - Weekly #Bulletin No. 7 - 28 August 2025 (summary)

 

{Summary}

-- During surveillance week from 21 to 27 August, 79 new confirmed human cases of West Nile Virus infection have been reported. 

-- Since the beginning of the epidemic season, the total number of confirmed cases have risen to 430 (they were 351 in the last bulletin); of these:

- 193 were West Nile Neuroinvasive Disease cases: 8 in Piedmont, 12 Lombardy, 14 Veneto, 1 Friuli-Venezia Giulia, 1 Liguria, 13 Emilia-Romagna, 62 Latium, 2 Molise, 64 Campania, 2 Basilicata, 5 Calabria, 1 Sicily, 8 Sardinia), 

- 38 were asymptomatic cases among blood donors, 

- 193 were West Nile Fever cases, 

- 3 asymptomatic and 

- 3 unspecified cases. 

-- Among the confirmed cases, there were 27 fatalities: 1 Piedmont, 1 Lombardy, 1 Emilia-Romagna, 11 Latium, 11 Campania, 2 Calabria). 

- The Case-Fatality Rate in WNND cases is so far at 13.9% (during 2018 it was 20%, in 2024 14%). 

-- One confirmed human case of Usutu virus infection has been confirmed in Latium's province of Latina. 

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_07.pdf

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#Italy, Integrated #Surveillance for #WNV and #USUV - Weekly #Bulletin no. 6 - August 21 2025 (summary): 76 new cases, total so far 351

{Summary}

-- During current surveillance week (14 to 20 August), seventy-six new human confirmed cases of West Nile Virus infection have been reported;

-- So far this year, 351 human cases of WNV infection were confirmed (they were 275 last week); of these:

- 158 were WNND (West Nile Neuroinvasive Disease): 6 in Piedmont, 8 Lombardy, 10 Veneto, 1 Friuli-Venezia Giulia, 8 Emilia-Romagna, 59 Latium, 54 Campania, 2 Basilicata, 5 Calabria, 5 Sardinia;

- 27 were asymptomatic cases in blood donors, 

- 162 were West Nile Fever cases, 

- 2 asymptomatic and 

- 2 symptomatic (unspecified). 

-- Among confirmed cases, there were 22 fatalities: 1 in Piedmont, 1 Lombardy, 10 Latium, 9 Campania, 1 Calabria). 

- The Case-Fatality Rate in WNND cases is thus far at 13.9% (in 2018 it was 20%, and in 2024, 14%). 

-- No confirmed cases of Usutu Virus infection have been confirmed this week.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_06.pdf

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#Italy, Integrated #Surveillance for #WNV & #Usutu Virus - Weekly Bulletin No. 5 (August 14 '25): 102 new human cases

 

{Summary}

• During current week (7-13 August '25), 102 new cases of human infection with West Nile Virus have been reported; 

• Total Number of Confirmed Cases so far this season have risen to 275 (they were 173 in the last report); 

-- among these: 

- 126 were West Nile Neuroinvasive Disease (WNND): 6 in Piedmont, 7 Lombardy, 5 Veneto, 1 FriuliVenezia Giulia, 4 Emilia-Romagna, 47 Latium, 50 Campania, 1 Basilicata, 3 Calabria, 2 Sardinia, 

- 20 asymptomatic cases among blood donors; 

- 125 West Nile Fever cases, 

- 2 asymptomatic cases and 

- 2 unspecified cases. 

• So far, 19 fatal cases were reported: 1 in Piedmont, 1 Lombardy, 8 Latium, 8 Campania, 1 Calabria. 

-- The Case-Fatality Rate of WNND cases is at 15,1% (during 2018 it was 20%, in 2024 14%). 

• No confirmed cases of Usutu Virus human infection were reported during current week. 

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_05.pdf

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#Italy, #WNV and #Usutu Virus Weekly #Surveillance #Bulletin No. 4, July 7 '25: 84 new confirmed cases (ISS)

{Summary}

-- Since the last update (July 31), eighty-four new confirmed cases of human infection with West Nile Virus have been reported. 

-- Since the start of epidemic season, there were 173 confirmed WNV cases, of which: 

- 72 were West Nile Neuroinvasive Disease (WNND): (2 in Piedmont, 2 Lombardy, 4 Veneto, 1 Friuli-Venezia Giulia, 2 Emilia-Romagna, 37 Latium, 21 Campania, 1 Basilicata, 1 Sardegna), 

- 14 were asymptomatic cases in blood donors, 

- 85 were West Nile Fever cases, 

- 1 was an asymptomatic case 

-- Among the confirmed cases, there were eleven fatalities: 1 in Piedmont, 4 Latium, 6 . 

- The case-fatality rate among WNND cases is at 15% (during 2018 season it was 20%, whereas in 2024 it was 14%). 

-- No new confirmed cases of Usutu Virus human infection have been reported during current surveillance week.

(...)

Source: High Institute of Health, https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2025_04.pdf

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#Italy, Integrated #WNV & #USUV #Surveillance - Bulletin no. 3, July 31 2025 (IZS Teramo): 57 new human cases reported

{Excerpts}

During the epidemiological week comprised between 24 and 30 July 2025, there were fifty-seven new confirmed cases of human infection with West Nile Virus.

-- Since the start of the epidemic season, eighty-nine cases have been reported (there were thirty-two cases in the last week report), of which:

-- forty were WNND (West Nile Neuroinvasive Disease):

- 2 cases in Piedmont, 1 Lombardy, 3 Veneto, 1 Emilia-Romagna, twenty-three Latium, ten Campania);

-- two cases of asymptomatic infection were detected among blood donors (one in Veneto and one in Campania);

-- forty-six cases of West Nile Fever have been confirmed: 

- one in Lombardy, five in Veneto, thirty-five in Latium, four in Campania, one in Sardinia;

-- one asymptomatic case is from Campania;

-- Among confirmed cases, eight fatalities have been recorded: one in Piedmont, two in Latium and five in Campania. The case-fatality rate among WNND so far is at 20% (during epidemic seasons 2018 it was 20% and in 2024, 14%). 

-- The first case of the 2025 season was reported in Piedmont (a sporadic case in Novara Province). The second case was notified on July 3 in Modena Town. 

-- In the current epidemiological week, no confirmed human cases of infection with Usutu virus have been reported.

(...)

Source: National Veterinary Institute of Teramo, https://westnile.izs.it/j6_wnd/home

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