IntroductionIn 2020, the first Dutch West Nile virus (WNV) infected birds were detected through risk-targeted surveillance of songbirds. Retrospective testing of patients with unexplained... Show moreIntroductionIn 2020, the first Dutch West Nile virus (WNV) infected birds were detected through risk-targeted surveillance of songbirds. Retrospective testing of patients with unexplained neurological disease revealed human WNV infections in July and August 2020. Bird ringers are highly exposed to mosquito bites and possibly avian excrements during ringing activities. This study therefore investigates whether bird ringers are at higher risk of exposure to WNV and Usutu virus (USUV).MethodsDutch bird ringers were asked to provide a single serum sample (May – September 2021) and to fill out a survey. Sera were screened by protein microarray for presence of specific IgG against WNV and USUV non-structural protein 1 (NS1), followed by focus reduction virus neutralization tests (FRNT). Healthcare workers (2009–2010), the national immunity cohort (2016–2017) and blood donors (2021) were used as control groups without this occupational exposure.ResultsThe majority of the 157 participating bird ringers was male (132/157, 84%) and the median age was 62 years. Thirty-seven participants (37/157, 23.6%) showed WNV and USUV IgG microarray signals above background, compared to 6.4% (6/94) in the community cohort and 2.1% (2/96) in blood donors (p < 0.01). Two seroreactive bird ringers were confirmed WNV or USUV positive by FRNT. The majority of seroreactive bird ringers travelled to EU countries with reported WNV human cases (30/37, 81%) (p = 0.07). No difference was observed between bird ringers with and without previous yellow fever vaccination.DiscussionThe higher frequency of WNV and/or USUV IgG reactive bird ringers indicates increased flavivirus exposure compared to the general population, suggesting that individuals with high-exposure professions may be considered to complement existing surveillance systems. However, the complexity of serological interpretation in relation to location-specific exposure (including travel), and antibody cross-reactivity, remain a challenge when performing surveillance of emerging flaviviruses in low-prevalence settings. Show less
The Flavivirus genus contains nearly 80 viruses, including many important human pathogens such as dengue virus, yellow fever virus, West Nile virus and tick-borne encephalitis virus. To reduce and... Show moreThe Flavivirus genus contains nearly 80 viruses, including many important human pathogens such as dengue virus, yellow fever virus, West Nile virus and tick-borne encephalitis virus. To reduce and prevent the impact of flavivirus infection on society, vaccines and effective therapies are required. However, this can only be achieved by increasing our knowledge regarding fundamental aspects of the molecular biology of flaviviruses and a better understanding of the interactions between the virus, the host and the vector. Flaviviruses are small, enveloped viruses containing a positive single-stranded RNA genome of approximately 11 kb with a 5__-cap structure and a non-polyadenylated 3__ end. The flavivirus 3__ untranslated region (UTR) is known to be important for replication and translation of the viral genome. The 3__ UTR contains well conserved RNA sequences and is predicted to fold into a highly complex structure involving several stem-loops and RNA pseudoknots. Some of these motifs and structures have been studied in detail and attributed a biological function, although only a small fraction of the predicted structures has been confirmed by probing. The aim of this thesis was to characterize and determine the biological function of RNA elements present in the flavivirus 3__ UTR. Show less
