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Usutu virus (USUV) is a mosquito-borne flavivirus, which shares its transmission cycle with the phylogenetically related West Nile virus (WNV). USUV circulates in several European countries and its activity has increased over the last 5 years.


To describe human cases of USUV infection identified by surveillance for WNV and USUV infection in the Veneto Region of northern Italy in 2018.


From 1 June to 30 November 2018, all cases of suspected autochthonous arbovirus infection and blood donors who had a reactive WNV nucleic acid test were investigated for both WNV and USUV infection by in-house molecular methods. Anti-WNV and anti-USUV IgM and IgG antibodies were detected by ELISA and in-house immunofluorescence assay, respectively; positive serum samples were further tested by WNV and USUV neutralisation assays run in parallel.


Eight cases of USUV infection (one with neuroinvasive disease, six with fever and one viraemic blood donor who developed arthralgia and myalgia) and 427 cases of WNV infection were identified. A remarkable finding of this study was the persistence of USUV RNA in the blood and urine of three patients during follow-up. USUV genome sequences from two patients shared over 99% nt identity with USUV sequences detected in mosquito pools from the same area and clustered within lineage Europe 2.


Clinical presentation and laboratory findings in patients with USUV infection were similar to those found in patients with WNV infection. Cross-reactivity of serology and molecular tests challenged the differential diagnosis.


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  1. Barzon L. Ongoing and emerging arbovirus threats in Europe. J Clin Virol. 2018;107:38-47.  https://doi.org/10.1016/j.jcv.2018.08.007  PMID: 30176404 
  2. Woodall JP. The viruses isolated from arthropods at the East African Virus Research Institute in the 26 years ending December 1963. Proc E Afr Acad. 1964;2:141-6.
  3. Weissenböck H, Kolodziejek J, Url A, Lussy H, Rebel-Bauder B, Nowotny N. Emergence of Usutu virus, an African mosquito-borne flavivirus of the Japanese encephalitis virus group, central Europe. Emerg Infect Dis. 2002;8(7):652-6.  https://doi.org/10.3201/eid0807.020094  PMID: 12095429 
  4. Weissenböck H, Bakonyi T, Rossi G, Mani P, Nowotny N. Usutu virus, Italy, 1996. Emerg Infect Dis. 2013;19(2):274-7.  https://doi.org/10.3201/eid1902.121191  PMID: 23347844 
  5. Percivalle E, Sassera D, Rovida F, Isernia P, Fabbi M, Baldanti F, et al. Usutu virus antibodies in blood donors and healthy forestry workers in the Lombardy Region, Northern Italy. Vector Borne Zoonotic Dis. 2017;17(9):658-61.  https://doi.org/10.1089/vbz.2017.2126  PMID: 28759350 
  6. Grottola A, Marcacci M, Tagliazucchi S, Gennari W, Di Gennaro A, Orsini M, et al. Usutu virus infections in humans: a retrospective analysis in the municipality of Modena, Italy. Clin Microbiol Infect. 2017;23(1):33-7.  https://doi.org/10.1016/j.cmi.2016.09.019  PMID: 27677699 
  7. Pierro A, Gaibani P, Spadafora C, Ruggeri D, Randi V, Parenti S, et al. Detection of specific antibodies against West Nile and Usutu viruses in healthy blood donors in northern Italy, 2010-2011. Clin Microbiol Infect. 2013;19(10):E451-3.  https://doi.org/10.1111/1469-0691.12241  PMID: 23663225 
  8. Faggioni G, De Santis R, Pomponi A, Grottola A, Serpini GF, Meacci M, et al. Prevalence of Usutu and West Nile virus antibodies in human sera, Modena, Italy, 2012. J Med Virol. 2018;90(10):1666-8.  https://doi.org/10.1002/jmv.25230  PMID: 29797606 
  9. Bakonyi T, Jungbauer C, Aberle SW, Kolodziejek J, Dimmel K, Stiasny K, et al. Usutu virus infections among blood donors, Austria, July and August 2017 - Raising awareness for diagnostic challenges. Euro Surveill. 2017;22(41):17-00644.  https://doi.org/10.2807/1560-7917.ES.2017.22.41.17-00644  PMID: 29043962 
  10. Cadar D, Maier P, Müller S, Kress J, Chudy M, Bialonski A, et al. Blood donor screening for West Nile virus (WNV) revealed acute Usutu virus (USUV) infection, Germany, September 2016. Euro Surveill. 2017;22(14):30501.  https://doi.org/10.2807/1560-7917.ES.2017.22.14.30501  PMID: 28422005 
  11. Allering L, Jöst H, Emmerich P, Günther S, Lattwein E, Schmidt M, et al. Detection of Usutu virus infection in a healthy blood donor from south-west Germany, 2012. Euro Surveill. 2012;17(50):20341. PMID: 23241231 
  12. Gaibani P, Pierro AM, Cavrini F, Rossini G, Landini MP, Sambri V. False-positive transcription-mediated amplification assay detection of West Nile virus in blood from a patient with viremia caused by an Usutu virus infection. J Clin Microbiol. 2010;48(9):3338-9.  https://doi.org/10.1128/JCM.02501-09  PMID: 20592138 
  13. Carletti F, Colavita F, Rovida F, Percivalle E, Baldanti F, Ricci I, et al. Expanding Usutu virus circulation in Italy: detection in the Lazio region, central Italy, 2017 to 2018. Euro Surveill. 2019;24(3):1800649.  https://doi.org/10.2807/1560-7917.ES.2019.24.3.1800649  PMID: 30670139 
  14. Aberle SW, Kolodziejek J, Jungbauer C, Stiasny K, Aberle JH, Zoufaly A, et al. Increase in human West Nile and Usutu virus infections, Austria, 2018. Euro Surveill. 2018;23(43):1800545.  https://doi.org/10.2807/1560-7917.ES.2018.23.43.1800545  PMID: 30376913 
  15. Nikolay B, Diallo M, Boye CS, Sall AA. Usutu virus in Africa. Vector Borne Zoonotic Dis. 2011;11(11):1417-23.  https://doi.org/10.1089/vbz.2011.0631  PMID: 21767160 
  16. Cavrini F, Gaibani P, Longo G, Pierro AM, Rossini G, Bonilauri P, et al. Usutu virus infection in a patient who underwent orthotropic liver transplantation, Italy, August-September 2009. Euro Surveill. 2009;14(50):19448. PMID: 20070935 
  17. Pecorari M, Longo G, Gennari W, Grottola A, Sabbatini A, Tagliazucchi S, et al. First human case of Usutu virus neuroinvasive infection, Italy, August-September 2009. Euro Surveill. 2009;14(50):19446. PMID: 20070936 
  18. Santini M, Vilibic-Cavlek T, Barsic B, Barbic L, Savic V, Stevanovic V, et al. First cases of human Usutu virus neuroinvasive infection in Croatia, August-September 2013: clinical and laboratory features. J Neurovirol. 2015;21(1):92-7.  https://doi.org/10.1007/s13365-014-0300-4  PMID: 25361698 
  19. Simonin Y, Sillam O, Carles MJ, Gutierrez S, Gil P, Constant O, et al. Human Usutu virus infection with atypical neurologic presentation, Montpellier, France, 2016. Emerg Infect Dis. 2018;24(5):875-8.  https://doi.org/10.3201/eid2405.171122  PMID: 29664365 
  20. Italian Ministry of Health. Piano nazionale integrato di sorveglianza e risposta ai virus West Nile e Usutu – 2018. [National surveillance and response integrated plan for West Nile and Usutu viruses - 2018]. Rome: Italian Ministry of Health; 2018. Italian. Available from: http://www.trovanorme.salute.gov.it/norme/renderNormsanPdf?anno=2018&codLeg=65084&parte=1%20&serie=null
  21. Barzon L, Pacenti M, Franchin E, Pagni S, Martello T, Cattai M, et al. Excretion of West Nile virus in urine during acute infection. J Infect Dis. 2013;208(7):1086-92.  https://doi.org/10.1093/infdis/jit290  PMID: 23821721 
  22. Cavrini F, Della Pepa ME, Gaibani P, Pierro AM, Rossini G, Landini MP, et al. A rapid and specific real-time RT-PCR assay to identify Usutu virus in human plasma, serum, and cerebrospinal fluid. J Clin Virol. 2011;50(3):221-3.  https://doi.org/10.1016/j.jcv.2010.11.008  PMID: 21156352 
  23. Becker N, Jöst H, Ziegler U, Eiden M, Höper D, Emmerich P, et al. Epizootic emergence of Usutu virus in wild and captive birds in Germany. PLoS One. 2012;7(2):e32604.  https://doi.org/10.1371/journal.pone.0032604  PMID: 22389712 
  24. Manarolla G, Bakonyi T, Gallazzi D, Crosta L, Weissenböck H, Dorrestein GM, et al. Usutu virus in wild birds in northern Italy. Vet Microbiol. 2010;141(1-2):159-63.  https://doi.org/10.1016/j.vetmic.2009.07.036  PMID: 19720475 
  25. Scaramozzino N, Crance JM, Jouan A, DeBriel DA, Stoll F, Garin D. Comparison of flavivirus universal primer pairs and development of a rapid, highly sensitive heminested reverse transcription-PCR assay for detection of flaviviruses targeted to a conserved region of the NS5 gene sequences. J Clin Microbiol. 2001;39(5):1922-7.  https://doi.org/10.1128/JCM.39.5.1922-1927.2001  PMID: 11326014 
  26. Ravagnan S, Montarsi F, Cazzin S, Porcellato E, Russo F, Palei M, et al. First report outside Eastern Europe of West Nile virus lineage 2 related to the Volgograd 2007 strain, northeastern Italy, 2014. Parasit Vectors. 2015;8(1):418.  https://doi.org/10.1186/s13071-015-1031-y  PMID: 26265490 
  27. Venkatesan A, Tunkel AR, Bloch KC, Lauring AS, Sejvar J, Bitnun A, et al. , International Encephalitis Consortium. Case definitions, diagnostic algorithms, and priorities in encephalitis: consensus statement of the international encephalitis consortium. Clin Infect Dis. 2013;57(8):1114-28.  https://doi.org/10.1093/cid/cit458  PMID: 23861361 
  28. Barzon L, Pacenti M, Franchin E, Martello T, Lavezzo E, Squarzon L, et al. Clinical and virological findings in the ongoing outbreak of West Nile virus Livenza strain in northern Italy, July to September 2012. Euro Surveill. 2012;17(36):20260. PMID: 22971328 
  29. Lustig Y, Mannasse B, Koren R, Katz-Likvornik S, Hindiyeh M, Mandelboim M, et al. Superiority of West Nile Virus RNA detection in whole blood for diagnosis of acute infection. J Clin Microbiol. 2016;54(9):2294-7.  https://doi.org/10.1128/JCM.01283-16  PMID: 27335150 
  30. Barzon L, Pacenti M, Franchin E, Lavezzo E, Masi G, Squarzon L, et al. Whole genome sequencing and phylogenetic analysis of West Nile virus lineage 1 and lineage 2 from human cases of infection, Italy, August 2013. Euro Surveill. 2013;18(38):20591.  https://doi.org/10.2807/1560-7917.ES2013.18.38.20591  PMID: 24084339 
  31. Calzolari M, Chiapponi C, Bonilauri P, Lelli D, Baioni L, Barbieri I, et al. Co-circulation of two Usutu virus strains in Northern Italy between 2009 and 2014. Infect Genet Evol. 2017;51:255-62.  https://doi.org/10.1016/j.meegid.2017.03.022  PMID: 28341546 
  32. Katoh K, Standley DM. MAFFT: iterative refinement and additional methods. Methods Mol Biol. 2014;1079:131-46.  https://doi.org/10.1007/978-1-62703-646-7_8  PMID: 24170399 
  33. Nguyen LT, Schmidt HA, von Haeseler A, Minh BQ. IQ-TREE: a fast and effective stochastic algorithm for estimating maximum-likelihood phylogenies. Mol Biol Evol. 2015;32(1):268-74.  https://doi.org/10.1093/molbev/msu300  PMID: 25371430 

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