Low Seroprevalence of West Nile Virus in Blood Donors from Catalonia, Spain

Serosurvey of Blood Donors to Assess West Nile Virus Exposure, South-Central Spain

We analyzed West Nile Virus (WNV) exposure from 1,222 blood donors during 2017-2018 from an area of south-central Spain. Results revealed WNV seroprevalence of 0.08% (95% CI 0.004%-0.4%) in this population. Our findings underscore the need for continued surveillance and research to manage WNV infection in this region.

Report on the first two confirmed autochthonous cases of West Nile virus encephalitis in Catalonia, Spain

BACKGROUND

West Nile virus (WNV) is a mosquito-borne flavivirus that can cause Central Nervous System infection in humans. Previous autochthonous cases of WNV encephalitis have been described in Spain, but none in Catalonia.

MATERIALS AND METHODS

We report on the first two autochthonous cases of encephalitis in humans caused by the West Nile virus (WNV) diagnosed in Catalonia (northeastern region of Spain).

RESULTS

An old married couple presented with clinical and biological signs compatible with viral encephalitis. Acute and convalescent serum samples showed IgM and IgG positivity for WNV. In addition, IgM was also detected in cerebrospinal fluid in the male patient. The serological results were later confirmed by microneutralization assays.

CONCLUSIONS

WNV infection must be considered in patients presenting with meningoencephalitis with viral CSF characteristics when common pathogens are excluded.

Serosurvey for dengue virus infection among pregnant women in the West Nile virus enzootic community of El Paso Texas

All 4 dengue viruses (DENV) cause sporadic outbreaks of human disease in the Rio Grande Valley along the US-Mexico border. In addition, West Nile virus (WNV) is enzootic in most border communities, and is the only arbovirus known to cause human disease in the El Paso, Texas community. In an effort to determine if DENV were also endemic in the El Paso community, a serosurvey was conducted among mothers at the time of delivery of their babies in selected hospitals. Cord-blood plasma samples obtained from mothers were tested for DENV antibody by an enzyme-linked immuno-sorbent assay (ELISA), plaque reduction neutralization test (PRNT) and a multiplex microsphere immunoassay. All DENV antibody positive plasma samples were also tested for WNV antibody by the same assays to consider the possibility that DENV antibody positive samples reflected WNV cross reactive antibody. The results indicated that 0.74% (11/1,472) of the mothers had a previous DENV infection and that 3.3% (48/1,472) had a previous WNV infection. Of these mothers, 0.20% (3/1,472) had antibody to both DENV and WNV as evidence of infection by both viruses. The results indicated that 0.2% (3/1472) of the mothers were positive for antibody to only WNV envelope, thus suggesting an undetermined flavivirus infection. Although 6 of the 11 DENV antibody positive mothers did not have a history of travel to a DENV endemic country, the findings of this survey provided further evidence of local transmission of WNV and suggested the possibility of focal autochthonous transmission of DENV in the El Paso community.

Seropositivity of West Nile Virus Among Acute Febrile Patients in Southern Ethiopia

Background

West Nile virus (WNV) is one of the widely distributed arboviruses in the world, and it is a pathogen of both humans and animals. The evidence that supports the prevalence of the WNV infection in Ethiopia is very scarce. Hence, this study aimed to assess the seropositivity of WNV among patients with acute febrile illness.

Methods

This health institution-based descriptive cross-sectional study was conducted on 532 acute febrile patients from May to August 2016 in Arba Minch Zuria district selected public health facilities, Southern Ethiopia. A pre-structured questionnaire was used to collect socio-demographic and clinical related information of the participants through convenient sampling techniques. In addition, trained nurses who were working in the health centers were responsible for interviewing acute febrile patients. About 5 mL of venous blood was collected aseptically from each of the study participants for the screening of the WNV immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies using indirect immunofluorescence technique (IIFT) as per manufacturer’s protocol. Data analysis was done using statistical package for social sciences (SPSS) version 20 software and the results were presented by frequency and percentage using tables.

Results

A total number of 529 acute febrile patients (42.7% males and 57.3% females) were enrolled in the study with a response rate of 99.4%. The overall 7.4% of acute febrile patients were seropositive for WNV-specific IgG and the rate was higher in males (9.7%) when compared to females (5.6%). While the overall 4.5% were seropositive for WNV-specific IgM and the rate was 6.6% in males and 3.0% in females.

Conclusion

The finding of this study is an important alarm for clinicians/physicians to diagnose febrile patients in the divergent direction including with the diagnosis of flaviviruses. In addition, the finding will further contribute to understanding the epidemiology of WNV fever in Ethiopia and it will play a role in the delivery of public health measures to decrease the risk of WNV exposure in the areas.

Seroprevalence, risk factors and spatial distribution of West Nile virus in Jordan

Background

This is the first countrywide study of the seroprevalence, risk factors and spatial distribution of West Nile virus (WNV) in Jordan.

Methods

A cross-sectional sample of 801 participants was administered a comprehensive questionnaire survey and tested for WNV immunoglobulin G antibodies.

Results

The point seroprevalence rate for WNV infection was 8.61% (95% confidence interval 6.8 to 10.8). Multivariate regression analysis demonstrated that sex, age, climate, income and drinking water source were significantly associated with seropositivity (p≤0.05). Males had 1.73 greater odds of infection compared with females. Compared with 15 to 29-year-olds, adults 30-49 y old and adults ≥50 y old had 2.0 and 3.1 greater odds of infection, respectively. Individuals living in the Jordan Valley and Badia had 22.2 and 7.2 times greater odds of infection, respectively, compared with individuals living in the highlands. Households with an income of <US$750/month had 1.8 greater odds of infection compared with those with higher household incomes. Individuals using spring lakes as a drinking water source had 5.1 greater odds of infection than people who used water from any other source.

Conclusions

This study demonstrates that WNV is circulating in Jordan and should be considered as a differential diagnosis in medical cases presenting with nervous system symptoms, especially for older populations living in the Jordan Valley and Badia areas.

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.

Spatial distribution of West Nile virus in humans and mosquitoes in Israel, 2000-2014

OBJECTIVES

Israel has a long history of West Nile virus (WNV) morbidity, and the rate of detection of WNV in mosquitoes has been high since 2000. The aim of this study was to integrate several WNV datasets in order to gain an insight into the geographical distribution of WNV in Israel.

METHODS

Three choropleth maps were generated showing WNV human morbidity, WNV prevalence in mosquitoes, and the results of a nationwide serological survey, based on the division of Israel into 15 sub-districts.

RESULTS

The maps show a high endemicity of WNV in Israel. In respect to the morbidity map, the population residing in the central part of the country and in Arava Region is at higher risk of developing the disease than the population of the rest of Israel. Interestingly, high prevalence rates of both WNV serology and WNV-infected mosquitoes were detected in Arava Region, but lower prevalence rates were detected in most areas of the coastal region, suggesting that other factors might also be important in the development of symptomatic WNV infections.

CONCLUSIONS

These results underline the high prevalence of WNV in Israel and point to specific risk areas for WNV infections across the country.

The seroprevalence of West Nile Virus in Israel: A nationwide cross sectional study

West Nile Virus (WNV) is endemic in Israel, affecting yearly 40-160 individuals. Israel is located on a central migratory path between Africa and Eurasia and most West Nile Fever (WNF) cases reported in recent years were among residents of the coastal plain. The aim of the study was to evaluate the seroprevalence of WNV among the Israeli population and to assess correlates for WNV infection. A cross-sectional nationwide serologic survey was conducted using 3,145 serum samples collected by the national Israeli serum bank during 2011-2014, representing all age and population groups in Israel. Prevalence rates of WNV IgG antibodies were determined. Logistic regressions models were applied to assess the associations between demographic characteristics and WNV seropositivity. 350 samples were positive to WNV (11.1%; 95%CI: 10.0-12.3%). In the multivariable analysis, there was a significant association between seropositivity and the Arab population group vs. Jews and others (OR = 1.86, 95%CI: 1.37-2.52), the time lived in Israel [50-59 years vs. 0-9 years; OR = 10.80 (95%CI: 1.03-113.46) and ≥60 years vs. 0-9 years; OR = 14.00 (1.32-148.31)] residence area] Coastal Plain, Inland Plain (Shfela) and Great Rift Valley vs. Upper Galilee; OR = 2.24 (95%CI: 1.37-3.65), OR = 2.18 (95%CI: 1.18-4.03), OR = 1.90 (95%CI: 1.10-3.30), respectively [and rural vs. urban settlement (OR = 1.65, 95%CI: 1.26-2.16). People, who reside in the Coastal Plain, Inland Plain and Great Rift Valley, should be aware of the risk of contracting WNV and reduce exposure to mosquito bites, using insect repellents, and wearing protective clothing. The Ministry of Environmental Protection should be active in reducing the mosquito population by eliminating sources of standing water, a breeding ground for mosquitoes.