West Nile Virus, cos’è, come contagia e qual è il rischio

Scritto da Matteo Morreale
Contenuti dell'articolo

Il primo decesso in Italia nel 2024 per il virus del Nilo occidentale ha attirato l’attenzione, ma è importante affrontare la situazione con calma e informarsi correttamente. La malattia da West Nile Virus (WNV), sebbene possa sembrare allarmante, raramente causa gravi complicazioni. In questo articolo, vedremo di cosa si tratta, come proteggersi e come mantenere la serenità.

Che cos’è il west nile virus?

Il West Nile Virus è un virus originario dell’Africa, ora diffuso in molte parti del mondo, compresa l’Italia. Appartiene al complesso antigenico del virus dell’encefalite giapponese, condividendo con esso alcune caratteristiche antigeniche. Cosa significa? Che alcuni degli elementi strutturali e proteici del virus sono riconosciuti dal nostro sistema immunitario.

Il virus viene trasmesso principalmente dalle zanzare infette, che acquisiscono il virus nutrendosi di sangue di uccelli infetti. Gli esseri umani e altri mammiferi possono essere infettati tramite la puntura di queste zanzare, ma il virus non si trasmette da persona a persona.

Ovviamente, come praticamente qualunque malattia, vanno inclusi i casi di trasfusioni infette o trapianti di organi infetti il virus. Non penso di doverlo precisare ma.. meglio dirlo.

Altre malattie trasmesse con vettori

Molte persone non sanno che numerosi virus non si trasmettono da uomo a uomo, ma necessitano di un vettore, come una zanzara, per diffondersi. Alcuni esempi includono:

  • Dengue
  • Zika
  • Chikungunya
  • Lyme
  • Malaria
  • tante altre.

Qual è il rischio di contrarre la malattia?

La maggior parte delle persone infette dal WNV non presenta sintomi o manifesta solo sintomi lievi, come febbre, mal di testa, dolori muscolari, nausea o eruzioni cutanee. In rari casi, l’infezione può causare gravi malattie come l’encefalite o la meningite, specialmente negli anziani o in persone con un sistema immunitario compromesso.

Quali sono i dati dalla letteratura scientifica

  • Circa il 25% degli infetti sviluppa la febbre da virus del Nilo occidentale.
  • Solo 1 su 150-250 infetti sviluppa una malattia neuroinvasiva.
  • Il rischio di complicanze gravi è maggiore con l’età avanzata, in presenza di tumori (specialmente malignità ematologiche) o dopo un trapianto d’organo.
  • La mortalità tra coloro che sviluppano complicanze neuroinvasive è del 10%.

Come proteggersi

La prevenzione è essenziale per proteggersi dal West Nile Virus. Ecco alcune misure semplici ma efficaci:

  • Utilizzare repellenti per insetti: Specialmente quando si è all’aperto.
  • Installare zanzariere: Su finestre e porte per impedire l’ingresso delle zanzare.
  • Rimuovere l’acqua stagnante: Intorno alla casa, poiché le zanzare depongono le uova in queste aree.

Queste precauzioni possono ridurre significativamente il rischio di infezione. In caso di sintomi sospetti, è fondamentale consultare un medico per una diagnosi accurata.

Paper e pubblicazioni sul West Nile Virus

  1. Zou S, Foster GA, Dodd RY, et al. West Nile fever characteristics among viremic persons identified through blood donor screening. J Infect Dis 2010; 202:1354.
  2. Lindsey NP, Staples JE, Lehman JA, et al. Surveillance for human West Nile virus disease – United States, 1999-2008. MMWR Surveill Summ 2010; 59:1.
  3. Carson PJ, Borchardt SM, Custer B, et al. Neuroinvasive disease and West Nile virus infection, North Dakota, USA, 1999-2008. Emerg Infect Dis 2012; 18:684.
  4. Sutinen J, Fell DB, Sander B, Kulkarni MA. Comorbid conditions as risk factors for West Nile neuroinvasive disease in Ontario, Canada: a population-based cohort study. Epidemiol Infect 2022; 150:e103.
  5. Visentin A, Nasillo V, Marchetti M, et al. Clinical Characteristics and Outcome of West Nile Virus Infection in Patients with Lymphoid Neoplasms: An Italian Multicentre Study. Hemasphere 2020; 4:e395.
  6. Patnaik JL, Harmon H, Vogt RL. Follow-up of 2003 human West Nile virus infections, Denver, Colorado. Emerg Infect Dis 2006; 12:1129.
  7. Nett RJ, Kuehnert MJ, Ison MG, et al. Current practices and evaluation of screening solid organ donors for West Nile virus. Transpl Infect Dis 2012; 14:268.
  8. Winston DJ, Vikram HR, Rabe IB, et al. Donor-derived West Nile virus infection in solid organ transplant recipients: report of four additional cases and review of clinical, diagnostic, and therapeutic features. Transplantation 2014; 97:881.
  9. Soto RA, McDonald E, Annambhotla P, et al. West Nile Virus Transmission by Solid Organ Transplantation and Considerations for Organ Donor Screening Practices, United States. Emerg Infect Dis 2022; 28:403.
  10. Kumar D, Drebot MA, Wong SJ, et al. A seroprevalence study of West Nile virus infection in solid organ transplant recipients. Am J Transplant 2004; 4:1883.
  11. Freifeld AG, Meza J, Schweitzer B, et al. Seroprevalence of West Nile virus infection in solid organ transplant recipients. Transpl Infect Dis 2010; 12:120.
  12. Glass WG, McDermott DH, Lim JK, et al. CCR5 deficiency increases risk of symptomatic West Nile virus infection. J Exp Med 2006; 203:35.
  13. Lim JK, McDermott DH, Lisco A, et al. CCR5 deficiency is a risk factor for early clinical manifestations of West Nile virus infection but not for viral transmission. J Infect Dis 2010; 201:178.
  14. Murray K, Baraniuk S, Resnick M, et al. Risk factors for encephalitis and death from West Nile virus infection. Epidemiol Infect 2006; 134:1325.
  15. Bode AV, Sejvar JJ, Pape WJ, et al. West Nile virus disease: a descriptive study of 228 patients hospitalized in a 4-county region of Colorado in 2003. Clin Infect Dis 2006; 42:1234.
  16. Goates C, Tsuha S, Working S, et al. Seronegative West Nile Virus Infection in a Patient Treated with Rituximab for Rheumatoid Arthritis. Am J Med 2017; 130:e257.
  17. Owens M, Choe L, Rivera JE, Avila JD. West Nile virus neuroinvasive disease associated with rituximab therapy. J Neurovirol 2020; 26:611.
  18. Nash D, Mostashari F, Fine A, et al. The outbreak of West Nile virus infection in the New York City area in 1999. N Engl J Med 2001; 344:1807.
  19. Orton SL, Stramer SL, Dodd RY. Self-reported symptoms associated with West Nile virus infection in RNA-positive blood donors. Transfusion 2006; 46:272.
  20. Brown JA, Factor DL, Tkachenko N, et al. West Nile viremic blood donors and risk factors for subsequent West Nile fever. Vector Borne Zoonotic Dis 2007; 7:479.
  21. Pealer LN, Marfin AA, Petersen LR, et al. Transmission of West Nile virus through blood transfusion in the United States in 2002. N Engl J Med 2003; 349:1236.
  22. Murray K, Walker C, Herrington E, et al. Persistent infection with West Nile virus years after initial infection. J Infect Dis 2010; 201:2.
  23. Loeb M, Hanna S, Nicolle L, et al. Prognosis after West Nile virus infection. Ann Intern Med 2008; 149:232.
  24. Carson PJ, Konewko P, Wold KS, et al. Long-term clinical and neuropsychological outcomes of West Nile virus infection. Clin Infect Dis 2006; 43:723.
  25. Haaland KY, Sadek J, Pergam S, et al. Mental status after West Nile virus infection. Emerg Infect Dis 2006; 12:1260.
  26. Patel H, Sander B, Nelder MP. Long-term sequelae of West Nile virus-related illness: a systematic review. Lancet Infect Dis 2015; 15:951.
  27. Watson JT, Pertel PE, Jones RC, et al. Clinical characteristics and functional outcomes of West Nile Fever. Ann Intern Med 2004; 141:360.
  28. Ferguson DD, Gershman K, LeBailly A, Petersen LR. Characteristics of the rash associated with West Nile virus fever. Clin Infect Dis 2005; 41:1204.
  29. Petersen LR, Brault AC, Nasci RS. West Nile virus: review of the literature. JAMA 2013; 310:308.
  30. Huhn GD, Dworkin MS. Rash as a prognostic factor in West Nile virus disease. Clin Infect Dis 2006; 43:388.
  31. Davis LE, DeBiasi R, Goade DE, et al. West Nile virus neuroinvasive disease. Ann Neurol 2006; 60:286.
  32. Lindsey NP, Hayes EB, Staples JE, Fischer M. West Nile virus disease in children, United States, 1999-2007. Pediatrics 2009; 123:e1084.
  33. Gaensbauer JT, Lindsey NP, Messacar K, et al. Neuroinvasive arboviral disease in the United States: 2003 to 2012. Pediatrics 2014; 134:e642.
  34. Popescu CP, Florescu SA, Hasbun R, et al. Prediction of unfavorable outcomes in West Nile virus neuroinvasive infection – Result of a multinational ID-IRI study. J Clin Virol 2020; 122:104213.
  35. Sejvar JJ. Clinical manifestations and outcomes of West Nile virus infection. Viruses 2014; 6:606.
  36. Sejvar JJ, Haddad MB, Tierney BC, et al. Neurologic manifestations and outcome of West Nile virus infection. JAMA 2003; 290:511.
  37. Kramer LD, Li J, Shi PY. West Nile virus. Lancet Neurol 2007; 6:171.
  38. Sejvar JJ, Bode AV, Marfin AA, et al. West Nile virus-associated flaccid paralysis. Emerg Infect Dis 2005; 11:1021.
  39. Al-Shekhlee A, Katirji B. Electrodiagnostic features of acute paralytic poliomyelitis associated with West Nile virus infection. Muscle Nerve 2004; 29:376.
  40. Li J, Loeb JA, Shy ME, et al. Asymmetric flaccid paralysis: a neuromuscular presentation of West Nile virus infection. Ann Neurol 2003; 53:703.
  41. Jeha LE, Sila CA, Lederman RJ, et al. West Nile virus infection: a new acute paralytic illness. Neurology 2003; 61:55.
  42. Leis AA, Stokic DS, Webb RM, et al. Clinical spectrum of muscle weakness in human West Nile virus infection. Muscle Nerve 2003; 28:302.
  43. Sejvar JJ, Bode AV, Marfin AA, et al. West Nile Virus-associated flaccid paralysis outcome. Emerg Infect Dis 2006; 12:514.
  44. Ahmed S, Libman R, Wesson K, et al. Guillain-Barré syndrome: An unusual presentation of West Nile virus infection. Neurology 2000; 55:144.
  45. Park M, Hui JS, Bartt RE. Acute anterior radiculitis associated with West Nile virus infection. J Neurol Neurosurg Psychiatry 2003; 74:823.
  46. Almhanna K, Palanichamy N, Sharma M, et al. Unilateral brachial plexopathy associated with West Nile virus meningoencephalitis. Clin Infect Dis 2003; 36:1629.
  47. Jani C, Walker A, Al Omari O, et al. Acute transverse myelitis in West Nile Virus, a rare neurological presentation. IDCases 2021; 24:e01104.
  48. Pepperell C, Rau N, Krajden S, et al. West Nile virus infection in 2002: morbidity and mortality among patients admitted to hospital in southcentral Ontario. CMAJ 2003; 168:1399.
  49. Kanagarajan K, Ganesh S, Alakhras M, et al. West Nile virus infection presenting as cerebellar ataxia and fever: case report. South Med J 2003; 96:600.
  50. Garg S, Jampol LM. Systemic and intraocular manifestations of West Nile virus infection. Surv Ophthalmol 2005; 50:3.
  51. Bains HS, Jampol LM, Caughron MC, Parnell JR. Vitritis and chorioretinitis in a patient with West Nile virus infection. Arch Ophthalmol 2003; 121:205.
  52. Hershberger VS, Augsburger JJ, Hutchins RK, et al. Chorioretinal lesions in nonfatal cases of West Nile virus infection. Ophthalmology 2003; 110:1732.
  53. Vandenbelt S, Shaikh S, Capone A Jr, Williams GA. Multifocal choroiditis associated with West Nile virus encephalitis. Retina 2003; 23:97.
  54. Khairallah M, Ben Yahia S, Ladjimi A, et al. Chorioretinal involvement in patients with West Nile virus infection. Ophthalmology 2004; 111:2065.
  55. Chan CK, Limstrom SA, Tarasewicz DG, Lin SG. Ocular features of west nile virus infection in North America: a study of 14 eyes. Ophthalmology 2006; 113:1539.
  56. Rousseau A, Haigh O, Ksiaa I, et al. Ocular Manifestations of West Nile Virus. Vaccines (Basel) 2020; 8.
  57. Kaiser PK, Lee MS, Martin DA. Occlusive vasculitis in a patient with concomitant West Nile virus infection. Am J Ophthalmol 2003; 136:928.
  58. Kuchtey RW, Kosmorsky GS, Martin D, Lee MS. Uveitis associated with West Nile virus infection. Arch Ophthalmol 2003; 121:1648.
  59. Hasbun R, Garcia MN, Kellaway J, et al. West Nile Virus Retinopathy and Associations with Long Term Neurological and Neurocognitive Sequelae. PLoS One 2016; 11:e0148898.
  60. Montgomery SP, Chow CC, Smith SW, et al. Rhabdomyolysis in patients with west nile encephalitis and meningitis. Vector Borne Zoonotic Dis 2005; 5:252.
  61. Paddock CD, Nicholson WL, Bhatnagar J, et al. Fatal hemorrhagic fever caused by West Nile virus in the United States. Clin Infect Dis 2006; 42:1527.
  62. Georges AJ, Lesbordes JL, Georges-Courbot MC, et al. Fatal hepatitis from West Nile virus. Ann Inst Pasteur Virol 1988; 138:237.
  63. Perelman A, Stern J. Acute pancreatitis in West Nile Fever. Am J Trop Med Hyg 1974; 23:1150.
  64. Sherman-Weber S, Axelrod P. Central diabetes insipidus complicating West Nile encephalitis. Clin Infect Dis 2004; 38:1042.
  65. Pergam SA, DeLong CE, Echevarria L, et al. Myocarditis in West Nile Virus infection. Am J Trop Med Hyg 2006; 75:1232.
  66. Smith RD, Konoplev S, DeCourten-Myers G, Brown T. West Nile virus encephalitis with myositis and orchitis. Hum Pathol 2004; 35:254.
  67. O’Leary DR, Kuhn S, Kniss KL, et al. Birth outcomes following West Nile Virus infection of pregnant women in the United States: 2003-2004. Pediatrics 2006; 117:e537.
  68. Paisley JE, Hinckley AF, O’Leary DR, et al. West Nile virus infection among pregnant women in a northern Colorado community, 2003 to 2004. Pediatrics 2006; 117:814.
  69. Pridjian G, Sirois PA, McRae S, et al. Prospective study of pregnancy and newborn outcomes in mothers with West nile illness during pregnancy. Birth Defects Res A Clin Mol Teratol 2016; 106:716.
  70. Nguyen Q, Teran S, Snedeker J, et al. CNS sequelae in an infant with congenital West Nile virus infection. Infect Med 2005; 22:626.
  71. Alpert SG, Fergerson J, Noël LP. Intrauterine West Nile virus: ocular and systemic findings. Am J Ophthalmol 2003; 136:733.
  72. Murray KO, Garcia MN, Rahbar MH, et al. Survival analysis, long-term outcomes, and percentage of recovery up to 8 years post-infection among the Houston West Nile virus cohort. PLoS One 2014; 9:e102953.
  73. Hart J Jr, Tillman G, Kraut MA, et al. West Nile virus neuroinvasive disease: neurological manifestations and prospective longitudinal outcomes. BMC Infect Dis 2014; 14:248.
  74. Samaan Z, McDermid Vaz S, Bawor M, et al. Neuropsychological Impact of West Nile Virus Infection: An Extensive Neuropsychiatric Assessment of 49 Cases in Canada. PLoS One 2016; 11:e0158364.
  75. Tyler KL, Pape J, Goody RJ, et al. CSF findings in 250 patients with serologically confirmed West Nile virus meningitis and encephalitis. Neurology 2006; 66:361.
  76. Procop GW, Yen-Lieberman B, Prayson RA, Gordon SM. Mollaret-like cells in patients with West Nile virus infection. Emerg Infect Dis 2004; 10:753.
  77. Petropoulou KA, Gordon SM, Prayson RA, Ruggierri PM. West Nile virus meningoencephalitis: MR imaging findings. AJNR Am J Neuroradiol 2005; 26:1986.
  78. Zak IT, Altinok D, Merline JR, et al. West Nile virus infection. AJR Am J Roentgenol 2005; 184:957.
  79. Ali M, Safriel Y, Sohi J, et al. West Nile virus infection: MR imaging findings in the nervous system. AJNR Am J Neuroradiol 2005; 26:289.
  80. Gandelman-Marton R, Kimiagar I, Itzhaki A, et al. Electroencephalography findings in adult patients with West Nile virus-associated meningitis and meningoencephalitis. Clin Infect Dis 2003; 37:1573.
  81. Rodriguez AJ, Westmoreland BF. Electroencephalographic characteristics of patients infected with west nile virus. J Clin Neurophysiol 2007; 24:386.
  82. Flaherty ML, Wijdicks EF, Stevens JC, et al. Clinical and electrophysiologic patterns of flaccid paralysis due to West Nile virus. Mayo Clin Proc 2003; 78:1245.
  83. Arboviral Diseases, Neuroinvasive and Non-neuroinvasive 2015 Case Definition. Centers for Disease Control and Prevention. Available at: https://ndc.services.cdc.gov/case-definitions/arboviral-diseases-neuroinvasive-and-non-neuroinvasive-2015/. (Accessed on August 01, 2022).
  84. Prince HE, Tobler LH, Lapé-Nixon M, et al. Development and persistence of West Nile virus-specific immunoglobulin M (IgM), IgA, and IgG in viremic blood donors. J Clin Microbiol 2005; 43:4316.
  85. Busch MP, Kleinman SH, Tobler LH, et al. Virus and antibody dynamics in acute west nile virus infection. J Infect Dis 2008; 198:984.
  86. Roehrig JT, Nash D, Maldin B, et al. Persistence of virus-reactive serum immunoglobulin m antibody in confirmed west nile virus encephalitis cases. Emerg Infect Dis 2003; 9:376.
  87. Prince HE, Tobler LH, Yeh C, et al. Persistence of West Nile virus-specific antibodies in viremic blood donors. Clin Vaccine Immunol 2007; 14:1228.
  88. Staples JE, Gibney KB, Panella AJ, et al. Duration of West Nile Virus Immunoglobulin M Antibodies up to 81 Months Following West Nile Virus Disease Onset. Am J Trop Med Hyg 2022; 106:1721.
  89. Martin DA, Biggerstaff BJ, Allen B, et al. Use of immunoglobulin m cross-reactions in differential diagnosis of human flaviviral encephalitis infections in the United States. Clin Diagn Lab Immunol 2002; 9:544.
  90. Johnson BW, Kosoy O, Martin DA, et al. West Nile virus infection and serologic response among persons previously vaccinated against yellow fever and Japanese encephalitis viruses. Vector Borne Zoonotic Dis 2005; 5:137.
  91. Petersen LR, Busch MP. Transfusion-transmitted arboviruses. Vox Sang 2010; 98:495.
  92. Busch MP, Caglioti S, Robertson EF, et al. Screening the blood supply for West Nile virus RNA by nucleic acid amplification testing. N Engl J Med 2005; 353:460.
  93. Busch MP, Wright DJ, Custer B, et al. West Nile virus infections projected from blood donor screening data, United States, 2003. Emerg Infect Dis 2006; 12:395.
  94. Barzon L, Pacenti M, Ulbert S, Palù G. Latest developments and challenges in the diagnosis of human West Nile virus infection. Expert Rev Anti Infect Ther 2015; 13:327.
  95. Tilley PA, Fox JD, Jayaraman GC, Preiksaitis JK. Nucleic acid testing for west nile virus RNA in plasma enhances rapid diagnosis of acute infection in symptomatic patients. J Infect Dis 2006; 193:1361.
  96. Lustig Y, Mannasse B, Koren R, et al. Superiority of West Nile Virus RNA Detection in Whole Blood for Diagnosis of Acute Infection. J Clin Microbiol 2016; 54:2294.
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