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In 2018, there was a large West Nile virus (WNV) outbreak in northern Italy. We observed five atypical cases of WNV infection that were characterised by the presence of WNV RNA and WNV IgG at the time of diagnosis, but no IgM response during follow-up. Neutralisation assays demonstrated pre-existing Usutu virus immunity in all patients. Besides challenging diagnosis, the immunological crosstalk between the two viruses warrants further investigation on possible cross-protection or infection enhancement effects.


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  1. Ministero della Salute. 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
  2. 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 
  3. 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 
  4. Di Gennaro A, Lorusso A, Casaccia C, Conte A, Monaco F, Savini G. Serum neutralization assay can efficiently replace plaque reduction neutralization test for detection and quantitation of West Nile virus antibodies in human and animal serum samples. Clin Vaccine Immunol. 2014;21(10):1460-2.  https://doi.org/10.1128/CVI.00426-14  PMID: 25100824 
  5. 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 
  6. Nikolay B. A review of West Nile and Usutu virus co-circulation in Europe: how much do transmission cycles overlap? Trans R Soc Trop Med Hyg. 2015;109(10):609-18.  https://doi.org/10.1093/trstmh/trv066  PMID: 26286946 
  7. Barzon L, Squarzon L, Cattai M, Franchin E, Pagni S, Cusinato R, et al. West Nile virus infection in Veneto region, Italy, 2008-2009. Euro Surveill. 2009;14(31):19289.  https://doi.org/10.2807/ese.14.31.19289-en  PMID: 19660244 
  8. 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 
  9. 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 
  10. 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 
  11. 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 
  12. 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.
  13. 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 
  14. Barzon L, Pacenti M, Cusinato R, Cattai M, Franchin E, Pagni S, et al. Human cases of West Nile Virus infection in north-eastern Italy, 15 June to 15 November 2010. Euro Surveill. 2011;16(33):19949. PMID: 21871228 
  15. European Centre for Disease Prevention and Control (ECDC). West Nile Fever. Stockholm: ECDC; [last accessed 27 Apr 2019]. Available from: https://ecdc.europa.eu/en/west-nile-fever
  16. Salje H, Cummings DAT, Rodriguez-Barraquer I, Katzelnick LC, Lessler J, Klungthong C, et al. Reconstruction of antibody dynamics and infection histories to evaluate dengue risk. Nature. 2018;557(7707):719-23.  https://doi.org/10.1038/s41586-018-0157-4  PMID: 29795354 
  17. Barzon L, Percivalle E, Pacenti M, Rovida F, Zavattoni M, Del Bravo P, et al. Virus and antibody dynamics in travelers with acute Zika virus infection. Clin Infect Dis. 2018;66(8):1173-80.  https://doi.org/10.1093/cid/cix967  PMID: 29300893 
  18. Lobigs M, Diamond MS. Feasibility of cross-protective vaccination against flaviviruses of the Japanese encephalitis serocomplex. Expert Rev Vaccines. 2012;11(2):177-87.  https://doi.org/10.1586/erv.11.180  PMID: 22309667 
  19. Blázquez AB, Escribano-Romero E, Martín-Acebes MA, Petrovic T, Saiz JC. Limited susceptibility of mice to Usutu virus (USUV) infection and induction of flavivirus cross-protective immunity. Virology. 2015;482:67-71.  https://doi.org/10.1016/j.virol.2015.03.020  PMID: 25827530 
  20. Barzon L, Pacenti M, Sinigaglia A, Berto A, Trevisan M, Palù G. West Nile virus infection in children. Expert Rev Anti Infect Ther. 2015;13(11):1373-86.  https://doi.org/10.1586/14787210.2015.1083859  PMID: 26325613 

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