Continued circulation of mpox: an epidemiological and phylogenetic assessment, European Region, 2023 to 2024.

During the summer of 2023, the European Region experienced a limited resurgence of mpox cases following the substantial outbreak in 2022. This increase was characterised by asynchronous and bimodal increases, with countries experiencing peaks at different times. The demographic profile of cases during the resurgence was largely consistent with those reported previously. All available sequences from the European Region belonged to clade IIb. Sustained efforts are crucial to control and eventually eliminate mpox in the European Region.

Tularemia on the rise in Switzerland? A one health approach is needed!

In the last 10 years, an increase in tularemia cases has been observed in both humans and animals in Switzerland. In these, infection with Francisella tularensis, the causative agent of the zoonotic disease tularemia, can occur through arthropod vectors or contact to infected animals or exposure to contaminated environmental sources. Currently, we are only able to postulate potential aetiologies: (i) behavioral changes of humans with more exposure to endemic habitats of infected arthropod vectors; (ii) an increased rate of tularemia infected ticks; (iii) increasing number and geographical regions of tick biotopes; (iv) increasing and/or more diverse reservoir populations; (v) increasing presence of bacteria in the environment; (vi) raised awareness and increased testing among physicians; (vii) improved laboratory techniques including molecular testing. To approach these questions, a one-health strategy is necessary. A functioning collaboration between public health, human medicine, and diagnostic and veterinary units for the control of tularemia must be established. Furthermore, the public should be included within citizen-supported-science-projects.

Genome-wide support for incipient Tula hantavirus species within a single rodent host lineage.

Evolutionary divergence of viruses is most commonly driven by co-divergence with their hosts or through isolation of transmission after host shifts. It remains mostly unknown, however, whether divergent phylogenetic clades within named virus species represent functionally equivalent byproducts of high evolutionary rates or rather incipient virus species. Here, we test these alternatives with genomic data from two widespread phylogenetic clades in Tula orthohantavirus (TULV) within a single evolutionary lineage of their natural rodent host, the common vole Microtus arvalis. We examined voles from forty-two locations in the contact region between clades for TULV infection by reverse transcription (RT)-PCR. Sequencing yielded twenty-three TULV Central North and twenty-one TULV Central South genomes, which differed by 14.9-18.5 per cent at the nucleotide and 2.2-3.7 per cent at the amino acid (AA) level without evidence of recombination or reassortment between clades. Geographic cline analyses demonstrated an abrupt (<1 km wide) transition between the parapatric TULV clades in continuous landscape. This transition was located within the Central mitochondrial lineage of M. arvalis, and genomic single nucleotide polymorphisms showed gradual mixing of host populations across it. Genomic differentiation of hosts was much weaker across the TULV Central North to South transition than across the nearby hybrid zone between two evolutionary lineages in the host. We suggest that these parapatric TULV clades represent functionally distinct, incipient species, which are likely differently affected by genetic polymorphisms in the host. This highlights the potential of natural viral contact zones as systems for investigating the genetic and evolutionary factors enabling or restricting the transmission of RNA viruses.

Congenital syphilis in Switzerland: a retrospective cohort study, 2010 to 2019.

AIMS OF THE STUDY: We previously reported a re-emergence of syphilis from 2006 to 2009 with detection of congenital syphilis in Switzerland. This study aimed to reassess the incidence of children exposed to maternal syphilis during pregnancy and congenital syphilis in a following 10-year period in the canton of Zurich, the most populous canton in Switzerland with the highest incidences of syphilis. METHODS: Children were identified both by reviewing medical records at the four major neonatal and paediatric hospitals providing acute care in the canton of Zurich and by the serological database of the syphilis reference laboratory. Inclusion criteria for children were (a) date of birth in the period 2010-2019, (b) place of birth in the canton of Zurich, (c) evaluation for syphilis due to positive syphilis pregnancy screening and (d) age <1 year at diagnosis. Results were compared with epidemiological data provided by the Federal Office of Public Health (FOPH). RESULTS: We identified and evaluated 17 children after potential exposure to maternal syphilis. Residual antibodies of a past infection were found in 11 mothers. Six children were identified as having had real exposure to asymptomatic maternal syphilis. From an epidemiological perspective, the distribution of the cases followed a similar pattern as confirmed syphilis cases in women of childbearing age reported to the FOPH. No cases of congenital syphilis were observed. CONCLUSIONS: In contrast to the rise in syphilis infections, this study identified no cases of congenital syphilis in the canton of Zurich, Switzerland, in the period 2010-2019. Syphilis pregnancy screening may have prevented congenital syphilis by diagnosing and allowing adequate treatment of asymptomatic maternal syphilis.

Phylogeography of Francisella tularensis subspecies holarctica and epidemiology of tularemia in Switzerland.

Tularemia, an endemic disease that mainly affects wild animals and humans, is caused by Francisella tularensis subsp. holarctica (Fth) in Switzerland. The Swiss Fth population consist of multiple different subclades which are distributed throughout the country. The aim of this study is to characterize the genetic diversity of Fth in Switzerland and to describe the phylogeographic relationship of isolates by single nucleotide polymorphism (SNP) analysis. This analysis is combined with human surveillance data from reported cases over the last 10 years and in vitro and in silico antibiotic resistance tests to provide insight into the epidemiology of tularemia in Switzerland. We sequenced the whole genomes of 52 Fth strains of human or tick origin collected in Switzerland between 2009 and 2022 and analyzed together with all publicly available sequencing data of Swiss and European Fth. Next, we performed a preliminary classification with the established canonical single nucleotide polymorphism nomenclature. Furthermore, we tested 20 isolates from all main Swiss clades for antimicrobial susceptibility against a panel of antimicrobial agents. All 52 sequenced isolates from Switzerland belong to major clade B.6, specifically subclades B.45 and B.46, previously described in Western Europe. We were able to accurately reconstruct the population structure according to the global phylogenetic framework. No resistance to clinically recommended antibiotics could be identified in vitro or in silico in the western B.6 strains.

Genetic and biological characteristics of species A rotaviruses detected in common shrews suggest a distinct evolutionary trajectory.

Species A rotaviruses (RVAs) are important aetiological agents of severe diarrhoea in young children. They are also widely distributed in mammals and birds, and increasing evidence indicates the possibility of zoonotic transmission of RVA strains between animals and humans. Moreover, reassortment of the eleven segments of the RVA genome can result in rapid biological changes and may influence pathogenic properties. Here, the nearly complete genome of an RVA strain from a common shrew (Sorex araneus) was sequenced, which showed high nucleotide sequence similarity to additionally determined partial sequences from common shrew RVAs but only very low identity (below 68 per cent) to RVAs from other animal species and humans. New genotypes were assigned to most genome segments of the novel common shrew RVA strain KS14/269, resulting in the genome constellation G39-P[55]-I27-R26-C22-M22-A37-N26-T26-E30-H26. Phylogenetic analyses clustered the common shrew RVAs as ancestral branches of other mammalian and avian RVAs for most of the genome segments, which is in contrast to the phylogeny of the hosts. Nevertheless, conserved sequences typical for all RVAs were identified at the 5'- and 3'- non-coding segment termini. To explore whether the common shrew RVA can exchange genetic material with other mammalian RVAs by reassortment, a reverse genetics system based on the simian RVA strain SA11 was used. However, no viable reassortants could be rescued by exchanging the VP4-, VP6-, or VP7-encoding genome segment alone or in combinations. It can be concluded that highly divergent RVAs are present in common shrews, indicating an evolution of these viruses largely separated from other mammalian and avian RVAs. The zoonotic potential of the virus seems to be low but needs to be further analysed in future.

Host genetic factors associated with the range limit of a European hantavirus.

The natural host ranges of many viruses are restricted to very specific taxa. Little is known about the molecular barriers between species that lead to the establishment of this restriction or generally prevent virus emergence in new hosts. Here, we identify genomic polymorphisms in a natural rodent host associated with a strong genetic barrier to the transmission of European Tula orthohantavirus (TULV). We analysed the very abrupt spatial transition between two major phylogenetic clades in TULV across the comparatively much wider natural hybrid zone between evolutionary lineages of their reservoir host, the common vole (Microtus arvalis). Genomic scans of 79,225 single nucleotide polymorphisms (SNPs) in 323 TULV-infected host individuals detected 30 SNPs that were consistently associated with the TULV clades CEN.S or EST.S in two replicate sampling transects. Focusing the analysis on 199 voles with evidence of genomic admixture at the individual level (0.1-0.9) supported statistical significance for all 30 loci. Host genomic variation at these SNPs explained up to 37.6% of clade-specific TULV infections. Genes in the vicinity of associated SNPs include SAHH, ITCH and two members of the Syngr gene family, which are involved in functions related to immune response or membrane transport. This study demonstrates the relevance of natural hybrid zones as systems not only for studying processes of evolutionary divergence and speciation, but also for the detection of evolving genetic barriers for specialized parasites.

Convergent Loss of Chemoreceptors across Independent Origins of Slave-Making in Ants.

The evolution of an obligate parasitic lifestyle often leads to the reduction of morphological and physiological traits, which may be accompanied by loss of genes and functions. Slave-making ants are social parasites that exploit the work force of closely related ant species for social behaviors such as brood care and foraging. Recent divergence between these social parasites and their hosts enables comparative studies of gene family evolution. We sequenced the genomes of eight ant species, representing three independent origins of ant slavery. During the evolution of eusociality, chemoreceptor genes multiplied due to the importance of chemical communication in insect societies. We investigated the evolutionary fate of these chemoreceptors and found that slave-making ant genomes harbored only half as many gustatory receptors as their hosts', potentially mirroring the outsourcing of foraging tasks to host workers. In addition, parasites had fewer odorant receptors and their loss shows striking patterns of convergence across independent origins of parasitism, in particular in orthologs often implicated in sociality like the 9-exon odorant receptors. These convergent losses represent a rare case of convergent molecular evolution at the level of individual genes. Thus, evolution can operate in a way that is both repeatable and reversible when independent ant lineages lose important social traits during the transition to a parasitic lifestyle.

Spatial and Temporal Dynamics and Molecular Evolution of Tula orthohantavirus in German Vole Populations.

Tula orthohantavirus (TULV) is a rodent-borne hantavirus with broad geographical distribution in Europe. Its major reservoir is the common vole (Microtus arvalis), but TULV has also been detected in closely related vole species. Given the large distributional range and high amplitude population dynamics of common voles, this host-pathogen complex presents an ideal system to study the complex mechanisms of pathogen transmission in a wild rodent reservoir. We investigated the dynamics of TULV prevalence and the subsequent potential effects on the molecular evolution of TULV in common voles of the Central evolutionary lineage. Rodents were trapped for three years in four regions of Germany and samples were analyzed for the presence of TULV-reactive antibodies and TULV RNA with subsequent sequence determination. The results show that individual (sex) and population-level factors (abundance) of hosts were significant predictors of local TULV dynamics. At the large geographic scale, different phylogenetic TULV clades and an overall isolation-by-distance pattern in virus sequences were detected, while at the small scale (<4 km) this depended on the study area. In combination with an overall delayed density dependence, our results highlight that frequent, localized bottleneck events for the common vole and TULV do occur and can be offset by local recolonization dynamics.