Diagnosis of west nile virus human infections: overview and proposal of diagnostic protocols considering the results of external quality assessment studies.

West Nile virus, genus Flavivirus, is transmitted between birds and occasionally other animals by ornithophilic mosquitoes. This virus also infects humans causing asymptomatic infections in about 85% of cases and <1% of clinical cases progress to severe neuroinvasive disease. The virus also presents a threat since most infections remain unapparent. However, the virus contained in blood and organs from asymptomatically infected donors can be transmitted to recipients of these infectious tissues. This paper reviews the presently available methods to achieve the laboratory diagnosis of West Nile virus infections in humans, discussing the most prominent advantages and disadvantages of each in light of the results obtained during four different External Quality Assessment studies carried out by the European Network for 'Imported' Viral Diseases (ENIVD).

Detection of West Nile virus RNA (lineages 1 and 2) in an external quality assessment programme for laboratories screening blood and blood components for West Nile virus by nucleic acid amplification testing.

BACKGROUND: A second Italian external quality assessment programme was run in 2011 to assess the performance of blood transfusion centres in detecting West Nile virus RNA in plasma. MATERIALS AND METHODS: Each participant received two panels containing negative samples and samples positive for West Nile virus lineages 1 and 2, some of which with a viral concentration close to or below the 95% limit of detection of the respective commercial nucleic acid amplification test assay: the PROCLEIX WNV assay or the Cobas TaqScreen West Nile virus test. RESULTS: Eleven laboratories took part in the external quality assessment programme. All of them correctly identified the positive samples with a viral concentration above the 95% limit of detection. No false positive results or pre-/post-analytical errors were observed. DISCUSSION: The External quality assessment programme run in 2011 allowed participants to assess the performance of the nucleic acid amplification test methods applied in their seasonal routine screening of blood donations. The results confirm the 95% limit of detection reported by the test kits' manufacturers for both West Nile virus lineages.