Autochthonous West Nile virus infection in Germany: Increasing numbers and a rare encephalitis case in a kidney transplant recipient

Spatiotemporally Explicit Epidemic Model for West Nile Virus Outbreak in Germany: An Inversely Calibrated Approach

Since the first autochthonous transmission of West Nile Virus was detected in Germany (WNV) in 2018, it has become endemic in several parts of the country and is continuing to spread due to the attainment of a suitable environment for vector occurrence and pathogen transmission. Increasing temperature associated with a changing climate has been identified as a potential driver of mosquito-borne disease in temperate regions. This scenario justifies the need for the development of a spatially and temporarily explicit model that describes the dynamics of WNV transmission in Germany. In this study, we developed a process-based mechanistic epidemic model driven by environmental and epidemiological data. Functional traits of mosquitoes and birds of interest were used to parameterize our compartmental model appropriately. Air temperature, precipitation, and relative humidity were the key climatic forcings used to replicate the fundamental niche responsible for supporting mosquito population and infection transmission risks in the study area. An inverse calibration method was used to optimize our parameter selection. Our model was able to generate spatially and temporally explicit basic reproductive number (R0) maps showing dynamics of the WNV occurrences across Germany, which was strongly associated with the deviation from daily means of climatic forcings, signaling the impact of a changing climate in vector-borne disease dynamics. Epidemiological data for human infections sourced from Robert Koch Institute and animal cases collected from the Animal Diseases Information System (TSIS) of the Friedrich-Loeffler-Institute were used to validate model-simulated transmission rates. From our results, it was evident that West Nile Virus is likely to spread towards the western parts of Germany with the rapid attainment of environmental suitability for vector mosquitoes and amplifying host birds, especially short-distance migratory birds. Locations with high risk of WNV outbreak (Baden-Württemberg, Bavaria, Berlin, Brandenburg, Hamburg, North Rhine-Westphalia, Rhineland-Palatinate, Saarland, Saxony-Anhalt and Saxony) were shown on R0 maps. This study presents a path for developing an early warning system for vector-borne diseases driven by climate change.

West Nile Virus Emergence in Germany 2019: Looking for Hidden Human West Nile Virus Infections

Background: Autochthonous human West Nile virus (WNV) infections were notified in the infectious disease surveillance system in Germany in 2018 for the first time and every year since then. Since clinically apparent infections are infrequent, we conducted two studies to investigate subclinical infections of this emerging disease in Germany in 2019 to detect infections not visible to surveillance based on symptomatic infections: limited-scope blood donor testing and a serosurvey among employees at two Berlin zoos with a history of demonstrated WNV infections in animals. Methods: For the zoo study, employees of the two zoos in Berlin were invited to participate in the study in late 2019. Blood samples were drawn and tested for the presence of antibodies (immunoglobulin M [IgM] and immunoglobulin G [IgG]) against WNV, and two other flaviviruses present in Germany: Usutu virus and Tick-borne encephalitis virus (TBEV). For the study in blood donors, four blood establishments with collection sites in regions with documented WNV-infected animals in 2018 and 2019 participated in the study. All donations in these regions were tested for WNV genome from July to November 2019. Results: In the enzyme-linked immunosorbent assay, none of the 70 tested zoo employees were WNV IgM-positive, 8 were WNV IgG-positive, additional 2 participants had equivocal results. All 10 were negative in the virus neutralization test (VNT) for WNV, but positive in the VNT for TBEV. None of the 4273 samples from blood donors tested in areas with WNV-infected animals was positive for WNV-RNA. Conclusion: Our results indicate that WNV circulation in Germany, though clearly documented in animals in 2019, apparently affected very few humans. Still areas with WNV-positive animals remain risk areas for human infection as well.

Genomic epidemiology of West Nile virus in Europe

West Nile virus is one of the most widespread mosquito-borne zoonotic viruses, with unique transmission dynamics in various parts of the world. Genomic surveillance has provided important insights in the global patterns of West Nile virus emergence and spread. In Europe, multiple West Nile virus lineages have been isolated, with lineage 1a and 2 being the main lineages responsible for human infections. In contrast to North America, where a single introduction of lineage 1a resulted in the virus establishing itself in a new continent, at least 13 introductions of lineages 1a and 2 have occurred into Europe, which is likely a vast underestimation of the true number of introductions. Historically, lineage 1a was the main lineage circulating in Europe, but since the emergence of lineage 2 in the early 2000s, the latter has become the predominant lineage. This shift in West Nile virus lineage prevalence has been broadly linked to the expansion of the virus into northerly temperate regions, where autochthonous cases in animals and humans have been reported in Germany and The Netherlands. Here, we discuss how genomic analysis has increased our understanding of the epidemiology of West Nile virus in Europe, and we present a global Nextstrain build consisting of publicly available West Nile virus genomes (https://nextstrain.org/community/grubaughlab/WNV-Global). Our results elucidate recent insights in West Nile virus lineage dynamics in Europe, and discuss how expanded programs can fill current genomic surveillance gaps.

Whole genome sequencing reveals insights into hepatitis E virus genome diversity, and virus compartmentalization in chronic hepatitis E

BACKGROUND

Hepatitis E virus (HEV) is a leading cause of acute hepatitis and can cause chronic infections in immunocompromised patients. Although HEV infections can be treated with ribavirin, antiviral efficacy is hampered by resistance mutations, normally detected by virus sequencing.

OBJECTIVES

High-throughput sequencing (HTS) allows for cost-effective complete viral genome sequencing. This enables the discovery and delineation of new subtypes, and revised the recognition of quasispecies and putative resistance mutations. However, HTS is challenged by factors including low viral load, sample degradation, high host background, and high viral diversity.

STUDY DESIGN

We apply complete genome sequencing strategies for HEV, including a targeted enrichment approach. These approaches were used to investigate sequence diversity in HEV RNA-positive animal and human samples and intra-host diversity in a chronically infected patient.

RESULTS

Here, we describe the identification of potential novel subtypes in a blood donation (genotype 3) and in an ancient livestock sample (genotype 7). In a chronically infected patient, we successfully investigated intra-host virus diversity, including the presence of ribavirin resistance mutations. Furthermore, we found convincing evidence for HEV compartmentalization, including the central nervous system, in this patient.

CONCLUSIONS

Targeted enrichment of viral sequences enables the generation of complete genome sequences from a variety of difficult sample materials. Moreover, it enables the generation of greater sequence coverage allowing more advanced analyses. This is key for a better understanding of virus diversity. Investigation of existing ribavirin resistance, in the context of minorities or compartmentalization, may be critical in treatment strategies of HEV patients.

Belgian Culex pipiens pipiens are competent vectors for West Nile virus while Culex modestus are competent vectors for Usutu virus

BACKGROUND

West Nile virus (WNV) and Usutu virus (USUV) are emerging arthropod-borne viruses (arboviruses) in Europe transmitted by Culex mosquitoes. In Belgium, it is currently unknown which Culex species are competent vectors for WNV or USUV and if these mosquitoes carry Wolbachia, an endosymbiotic bacterium that can block arbovirus transmission. The aims of our study were to measure the vector competence of Belgian Culex mosquitoes to WNV and USUV and determine if a naturally acquired Wolbachia infection can influence virus transmission.

METHODOLOGY/PRINCIPAL FINDINGS

Female Culex mosquitoes were captured from urban and peri-urban sites in Leuven, Belgium and offered an infectious bloodmeal containing WNV lineage 2, USUV European (EU) lineage 3, or USUV African (AF) lineage 3. Blood-fed females were incubated for 14 days at 25°C after which the body, head, and saliva were collected to measure infection, dissemination, and transmission rates as well as transmission efficiency. Mosquito species were identified by qRT-PCR or Sanger sequencing, the presence of infectious virus in mosquitoes was confirmed by plaque assays, and viral genome copies were quantified by qRT-PCR. Culex pipiens pipiens were able to transmit WNV (4.3% transmission efficiency, n = 2/47) but not USUV (EU lineage: n = 0/56; AF lineage: n = 0/37). In contrast, Culex modestus were able to transmit USUV (AF lineage: 20% transmission efficiency, n = 1/5) but not WNV (n = 0/6). We found that the presence or absence of Wolbachia was species-dependent and did not associate with virus transmission.

CONCLUSIONS/SIGNIFICANCE

This is the first report that Belgian Culex mosquitoes can transmit both WNV and USUV, forewarning the risk of human transmission. More research is needed to understand the potential influence of Wolbachia on arbovirus transmission in Culex modestus mosquitoes.

An advanced sequence clustering and designation workflow reveals the enzootic maintenance of a dominant West Nile virus subclade in Germany

West Nile virus (WNV) is the most widespread arthropod-borne (arbo) virus and the primary cause of arboviral encephalitis globally. Members of WNV species genetically diverged and are classified into different hierarchical groups below species rank. However, the demarcation criteria for allocating WNV sequences into these groups remain individual and inconsistent, and the use of names for different levels of the hierarchical levels is unstructured. In order to have an objective and comprehensible grouping of WNV sequences, we developed an advanced grouping workflow using the 'affinity propagation clustering' algorithm and newly included the 'agglomerative hierarchical clustering' algorithm for the allocation of WNV sequences into different groups below species rank. In addition, we propose to use a fixed set of terms for the hierarchical naming of WNV below species level and a clear decimal numbering system to label the determined groups. For validation, we applied the refined workflow to WNV sequences that have been previously grouped into various lineages, clades, and clusters in other studies. Although our workflow regrouped some WNV sequences, overall, it generally corresponds with previous groupings. We employed our novel approach to the sequences from the WNV circulation in Germany 2020, primarily from WNV-infected birds and horses. Besides two newly defined minor (sub)clusters comprising only three sequences each, Subcluster 2.5.3.4.3c was the predominant WNV sequence group detected in Germany from 2018 to 2020. This predominant subcluster was also associated with at least five human WNV infections in 2019-20. In summary, our analyses imply that the genetic diversity of the WNV population in Germany is shaped by enzootic maintenance of the dominant WNV subcluster accompanied by sporadic incursions of other rare clusters and subclusters. Moreover, we show that our refined approach for sequence grouping yields meaningful results. Although we primarily aimed at a more detailed WNV classification, the presented workflow can also be applied to the objective genotyping of other virus species.

Encephalitis in travellers: A prospective multicentre study

BACKGROUND

As the epidemiology of encephalitis varies from one country to another, international travel may be an important clue for the diagnostic workout of this puzzling disease.

METHODS

We performed an ancillary study using the ENCEIF prospective cohort conducted in 62 clinical sites in France from 2016 to 2019. All cases of encephalitis in adults that fulfilled a case definition derived from the International Encephalitis Consortium were included. Travellers were defined as patients who spent at least one night in a foreign country within the last six months.

RESULTS

Of the 494 encephalitis patients enrolled, 69 (14%) were travellers. As compared to non-travellers, they were younger (median age, 48 years [interquartile range, 36-69] vs. 66 [49-76], P < 0.001), less likely to be immunocompromised: 2/69 (3%) vs 56/425 (13%), P = 0.02, and reported more arthralgia: 7/69 (10%) vs. 11/425 (3%), P = 0.007. The risk of poor outcome at hospital discharge (Glasgow outcome scale ≤ 3), was similar for travellers and for non-travellers after adjustment (aOR 0.80 [0.36-1.80], P = 0.594). Arboviruses were the main causes of encephalitis in travellers: 15/69 (22%) vs. 20/425 (5%) in non-travellers, P < 0.001, and Herpes simplex virus (HSV) was the second (9/69, 13%). Of note, in 19% (13/69) of cases, the risk of encephalitis in travellers may have been decreased with a vaccine.

CONCLUSION

The two primary causes of encephalitis in travellers are arboviruses, and HSV. Empirical treatment of encephalitis in travellers must include aciclovir. Pre-travel advice and vaccination may decrease the risk of encephalitis in travellers.