High Endemicity and Distinct Phylogenetic Characteristics of Sindbis Virus in Israel

Vector Competence of Northern European Culex pipiens Biotype pipiens and Culex torrentium to West Nile Virus and Sindbis Virus

The West Nile Virus (WNV) and Sindbis virus (SINV) are avian-hosted mosquito-borne zoonotic viruses that co-circulate in some geographical areas and share vector species such as Culex pipiens and Culex torrentium. These are widespread in Europe, including northern parts and Finland, where SINV is endemic, but WNV is currently not. As WNV is spreading northwards in Europe, we wanted to assess the experimental vector competence of Finnish Culex pipiens and Culex torrentium mosquitoes to WNV and SINV in different temperature profiles. Both mosquito species were found susceptible to both viruses and got infected via infectious blood meal at a mean temperature of 18 °C. WNV-positive saliva was detected at a mean temperature of 24 °C, whereas SINV-positive saliva was detected already at a mean temperature of 18 °C. Cx. torrentium was found to be a more efficient vector for WNV and SINV over Cx. pipiens. Overall, the results were in line with the previous studies performed with more southern vector populations. The current climate does not seem optimal for WNV circulation in Finland, but temporary summertime transmission could occur in the future if all other essential factors are in place. More field data would be needed for monitoring and understanding the northward spreading of WNV in Europe.

Arthritogenic alphaviruses: epidemiological and clinical perspective on emerging arboviruses

Mosquito-borne viruses, or arboviruses, have been part of the infectious disease landscape for centuries, and are often, but not exclusively, endemic to equatorial and subtropical regions of the world. The past two decades saw the re-emergence of arthritogenic alphaviruses, a genus of arboviruses that includes several members that cause severe arthritic disease. Recent outbreaks further highlight the substantial public health burden caused by these viruses. Arthritogenic alphaviruses are often reported in the context of focused outbreaks in specific regions (eg, Caribbean, southeast Asia, and Indian Ocean) and cause debilitating acute disease that can extend to chronic manifestations for years after infection. These viruses are classified among several antigenic complexes, span a range of hosts and mosquito vectors, and can be distributed along specific geographical locations. In this Review, we highlight key features of alphaviruses that are known to cause arthritic disease in humans and outline the present findings pertaining to classification, immunogenicity, pathogenesis, and experimental approaches aimed at limiting disease manifestations. Although the most prominent alphavirus outbreaks in the past 15 years featured chikungunya virus, and a large body of work has been dedicated to understanding chikungunya disease mechanisms, this Review will instead focus on other arthritogenic alphaviruses that have been identified globally and provide a comprehensive appraisal of present and future research directions.

Epidemic Alphaviruses: Ecology, Emergence and Outbreaks

Over the past century, the emergence/reemergence of arthropod-borne zoonotic agents has been a growing public health concern. In particular, agents from the genus Alphavirus pose a significant risk to both animal and human health. Human alphaviral disease presents with either arthritogenic or encephalitic manifestations and is associated with significant morbidity and/or mortality. Unfortunately, there are presently no vaccines or antiviral measures approved for human use. The present review examines the ecology, epidemiology, disease, past outbreaks, and potential to cause contemporary outbreaks for several alphavirus pathogens.

Presence of Antibodies against Sindbis Virus in the Israeli Population: A Nationwide Cross-Sectional Study

Sindbis virus (SINV) is a mosquito-borne alphavirus circulating globally. SINV outbreaks have been mainly reported in North-European countries. In Israel, SINV was detected in 6.3% of mosquito pools; however, SINV infection in humans has rarely been diagnosed. A serologic survey to detect SINV IgG antibodies was conducted to evaluate the seroprevalence of SINV in the Israeli population. In total, 3145 serum samples collected in 2011-2014, representing all age and population groups in Israel, were assessed using an indirect ELISA assay, and a neutralization assay was performed on all ELISA-positive samples. The prevalence rates of SINV IgG antibodies were calculated. Logistic regressions models were applied to assess the association between demographic characteristics and SINV seropositivity. Overall, 113 (3.6%) and 59 (1.9%) samples were positive for ELISA and neutralization SINV IgG, respectively. Multivariable analysis demonstrated that SINV seropositivity was significantly associated with older age and residence outside metropolitan areas. These results demonstrate that, despite no outbreaks or clinical presentation, SINV infects the human population in Israel. Seropositivity is countrywide, more frequent in people of older age, and less diffuse in Israel's metropolitan areas. Seroprevalence studies from other countries will add to our understanding of the global burden of SINV and the risk for potential SINV outbreaks.