West Nile virus infection in individuals with pre-existing Usutu virus immunity, northern Italy, 2018

Euro Surveill. 2019 May;24(21):1900261. doi: 10.2807/1560-7917.ES.2019.24.21.1900261.

Abstract

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.

Keywords: Usutu virus; West Nile virus; antibody cross-reactivity; cross-protection; secondary infection.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Animals
  • Antibodies, Neutralizing / blood
  • Antibodies, Viral / blood*
  • Culex / virology
  • Disease Outbreaks
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Flavivirus / genetics
  • Flavivirus / immunology*
  • Humans
  • Immunoglobulin G / blood
  • Italy / epidemiology
  • Male
  • Middle Aged
  • Neutralization Tests
  • Phylogeny
  • Polymerase Chain Reaction
  • Public Health Surveillance*
  • Real-Time Polymerase Chain Reaction
  • West Nile Fever / diagnosis*
  • West Nile Fever / epidemiology
  • West Nile Fever / virology
  • West Nile virus / genetics
  • West Nile virus / immunology
  • West Nile virus / isolation & purification*

Substances

  • Antibodies, Neutralizing
  • Antibodies, Viral
  • Immunoglobulin G

Supplementary concepts

  • Usutu virus