Zoonotic risk assessment among farmed mammals.

Farmed mammals may act as hosts for zoonotic viruses that can cause disease outbreaks in humans. This SnapShot shows which farmed mammals, and to what extent, are of particular risk of harboring and spreading viruses from viral families that are commonly associated with zoonotic disease. It also discusses genome surveillance methods and biosafety measures. To view this SnapShot, open or download the PDF.

Concurrent Infection With Multiple Human Papillomavirus Types Among Unvaccinated and Vaccinated 17-Year-Old Norwegian Girls.

BACKGROUND: Whether type-specific human papillomavirus (HPV) infection influences the risk of acquiring infections with other HPV types is unclear. We studied concurrent HPV infections in 17-year-old girls from 2 birth cohorts; the first vaccine-eligible cohort in Norway and a prevaccination cohort. METHODS: Urine samples were collected and tested for 37 HPV genotypes. This study was restricted to unvaccinated girls from the prevaccination cohort (n = 5245) and vaccinated girls from the vaccine-eligible cohort (n = 4904). Risk of HPV infection was modelled using mixed-effect logistic regression. Expected frequencies of concurrent infection with each pairwise combination of the vaccine types and high-risk types (6/11/16/18/31/33/35/39/45/51/52/56/58/59) were compared to observed frequencies. RESULTS: Infection with multiple HPV types was more common among unvaccinated girls than vaccinated girls (9.2% vs 3.7%). HPV33 and HPV51 was the only HPV pair that was detected together more often than expected among both unvaccinated (P = .002) and vaccinated girls (P < .001). No HPV pairs were observed significantly less often than expected. CONCLUSIONS: HPV33 and HPV51 tended to be involved in coinfection among both unvaccinated and vaccinated girls. The introduction of HPV vaccination does not seem to have had an effect on the tendency of specific HPV types to cluster together.

Circumpolar diversification of the Ixodes uriae tick virome.

Ticks (order: Ixodida) are a highly diverse and ecologically important group of ectoparasitic blood-feeding organisms. One such species, the seabird tick (Ixodes uriae), is widely distributed around the circumpolar regions of the northern and southern hemispheres. It has been suggested that Ix. uriae spread from the southern to the northern circumpolar region millions of years ago and has remained isolated in these regions ever since. Such a profound biographic subdivision provides a unique opportunity to determine whether viruses associated with ticks exhibit the same evolutionary patterns as their hosts. To test this, we collected Ix. uriae specimens near a Gentoo penguin (Pygoscelis papua) colony at Neko harbour, Antarctica, and from migratory birds-the Razorbill (Alca torda) and the Common murre (Uria aalge)-on Bonden island, northern Sweden. Through meta-transcriptomic next-generation sequencing we identified 16 RNA viruses, seven of which were novel. Notably, we detected the same species, Ronne virus, and two closely related species, Bonden virus and Piguzov virus, in both hemispheres indicating that there have been at least two cross-circumpolar dispersal events. Similarly, we identified viruses discovered previously in other locations several decades ago, including Gadgets Gully virus, Taggert virus and Okhotskiy virus. By identifying the same or closely related viruses in geographically disjunct sampling locations we provide evidence for virus dispersal within and between the circumpolar regions. In marked contrast, our phylogenetic analysis revealed no movement of the Ix. uriae tick hosts between the same locations. Combined, these data suggest that migratory birds are responsible for the movement of viruses at both local and global scales.

Field surveys in Croatia and North Macedonia reveal two novel phleboviruses circulating in sandflies.

Sandfly-borne phleboviruses are distributed widely throughout the Mediterranean Basin, presenting a threat to public health in areas where they circulate. However, the true diversity and distribution of pathogenic and apathogenic sandfly-borne phleboviruses remains a key issue to be studied. In the Balkans, most published data rely on serology-based studies although virus isolation has occasionally been reported. Here, we report the discovery of two novel sandfly-borne phleboviruses, provisionally named Zaba virus (ZABAV) and Bregalaka virus (BREV), which were isolated in Croatia and North Macedonia, respectively. This constitutes the first isolation of phleboviruses in both countries. Genetic analysis based on complete coding sequences indicated that ZABAV and BREV are distinct from each other and belong to the genus Phlebovirus, family Phenuiviridae. Phylogenetic and amino acid modelling of viral polymerase shows that ZABAV and BREV are new members of the Salehabad phlebovirus species and the Adana phlebovirus species, respectively. Moreover, sequence-based vector identification suggests that ZABAV is mainly transmitted by Phlebotomus neglectus and BREV is mainly transmitted by Phlebotomus perfiliewi. BREV neutralizing antibodies were detected in 3.3% of human sera with rates up to 16.7% in certain districts, demonstrating that BREV frequently infects humans in North Macedonia. In vitro viral growth kinetics experiments demonstrated viral replication of both viruses in mammalian and mosquito cells. In vivo experimental studies in mice suggest that ZABAV and BREV exhibit characteristics making them possible human pathogens.

The impact of public health interventions in the Nordic countries during the first year of SARS-CoV-2 transmission and evolution.

BackgroundMany countries have attempted to mitigate and control COVID-19 through non-pharmaceutical interventions, particularly with the aim of reducing population movement and contact. However, it remains unclear how the different control strategies impacted the local phylodynamics of the causative SARS-CoV-2 virus.AimWe aimed to assess the duration of chains of virus transmission within individual countries and the extent to which countries exported viruses to their geographical neighbours.MethodsWe analysed complete SARS-CoV-2 genomes to infer the relative frequencies of virus importation and exportation, as well as virus transmission dynamics, in countries of northern Europe. We examined virus evolution and phylodynamics in Denmark, Finland, Iceland, Norway and Sweden during the first year of the COVID-19 pandemic.ResultsThe Nordic countries differed markedly in the invasiveness of control strategies, which we found reflected in transmission chain dynamics. For example, Sweden, which compared with the other Nordic countries relied more on recommendation-based rather than legislation-based mitigation interventions, had transmission chains that were more numerous and tended to have more cases. This trend increased over the first 8 months of 2020. Together with Denmark, Sweden was a net exporter of SARS-CoV-2. Norway and Finland implemented legislation-based interventions; their transmission chain dynamics were in stark contrast to their neighbouring country Sweden.ConclusionSweden constituted an epidemiological and evolutionary refugium that enabled the virus to maintain active transmission and spread to other geographical locations. Our analysis reveals the utility of genomic surveillance where monitoring of active transmission chains is a key metric.

Introduction and Dispersal of Sindbis Virus from Central Africa to Europe.

Bird-hosted viruses have the potential to be transported over large areas of the world and to be transmitted in distant geographical regions. Sindbis virus (SINV) is a mosquito-borne alphavirus that is locally amplified in a bird-mosquito enzootic cycle and distributed all over the Old World and Australia/Oceania. Sindbis virus genotype I (SINV-I) is the cause of disease outbreaks in humans in South Africa as well as in northern Europe. To trace the evolutionary history and potential strain-disease association of SINV-I, we sequenced 36 complete genomes isolated from field material in Europe, as well as in Africa and the Middle East, collected over 58 years. These were analyzed together with 30 additional published whole SINV-I genomes using Bayesian analysis. Our results suggested that SINV-I was introduced only once to northern Europe from central Africa, in the 1920s. After its first introduction to Sweden, it spread east and southward on two separate occasions in the 1960s and 1970s. Another introduction from central Africa to southern/central Europe seems to have occurred, and where these two introductions meet, one recombination event was detected in central Europe. In addition, another recombinant strain was found in central Africa, where the most divergent SINV-I strains also originated.IMPORTANCE This study shows that only a single introduction of SINV into a new geographical area is required for spread and establishment, provided that the requisite vector(s) and reservoir(s) of epizootological and epidemiological importance are present. Furthermore, we present the first report of recombination between two strains of SINV in nature. Our study increases the knowledge on new introductions and dispersal of arboviruses in general and of SINV in particular.

Molecular epidemiology of hepatitis B virus infection in Norway.

BACKGROUND: Hepatitis B virus (HBV) infection remains a serious global health challenge. The widespread distribution of HBV is highlighted by multiple HBV genotypes associated with different geographical origin and transmission patterns, as well as, clinical outcomes. Investigating population HBV genotype composition and origin is therefore highly warranted. METHODS: In this molecular epidemiological study we analysed 1157 HBV S-gene sequences collected from patients in Norway, primarily in the period 2004-2011, and linked them to epidemiological data from the Norwegian surveillance system for communicable diseases. RESULTS: Of the patients with reported country of infection (n = 909), 10% (n = 93) were infected in Norway, but the majority (n = 816; 90%) stated that they became infected outside of Norway. Of the patients infected outside of Norway, most became infected in Southeast and East Asia (n = 465; 51%) and Central, West, and North Africa (n = 254; 28%). The distribution of HBV genotypes in Norway is dominated by genotype D (32%) followed by genotype A (22%), B and C (18 and 18%, respectively), and E (7%). Genotype B, C and E were phylogenetically categorized by a majority of sequences originating from distinct geographical regions, either Asia or Africa, whereas genotype A and D originated from multiple geographic regions. However, within genotype A and D, our molecular epidemiology analysis indicated a geographical clustering of sequences depending on their geographical origin. CONCLUSIONS: The majority of HBV patients in Norway became infected outside of Norway and were represented by most common genotypes. Patients stated to have been infected in Norway were found primarily within genotype A and D, and were phylogenetically characterized by both small local clusters and interspersed sequences that clustered with non-Norwegian sequences, indicating that a proportion of the patients assumed to have been infected in Norway likely became infected outside of Norway although assumed the contrary.

Armed conflict and population displacement as drivers of the evolution and dispersal of Mycobacterium tuberculosis.

The "Beijing" Mycobacterium tuberculosis (Mtb) lineage 2 (L2) is spreading globally and has been associated with accelerated disease progression and increased antibiotic resistance. Here we performed a phylodynamic reconstruction of one of the L2 sublineages, the central Asian clade (CAC), which has recently spread to western Europe. We find that recent historical events have contributed to the evolution and dispersal of the CAC. Our timing estimates indicate that the clade was likely introduced to Afghanistan during the 1979-1989 Soviet-Afghan war and spread further after population displacement in the wake of the American invasion in 2001. We also find that drug resistance mutations accumulated on a massive scale in Mtb isolates from former Soviet republics after the fall of the Soviet Union, a pattern that was not observed in CAC isolates from Afghanistan. Our results underscore the detrimental effects of political instability and population displacement on tuberculosis control and demonstrate the power of phylodynamic methods in exploring bacterial evolution in space and time.

The nucleotide composition of microbial genomes indicates differential patterns of selection on core and accessory genomes.

BACKGROUND: The core genome consists of genes shared by the vast majority of a species and is therefore assumed to have been subjected to substantially stronger purifying selection than the more mobile elements of the genome, also known as the accessory genome. Here we examine intragenic base composition differences in core genomes and corresponding accessory genomes in 36 species, represented by the genomes of 731 bacterial strains, to assess the impact of selective forces on base composition in microbes. We also explore, in turn, how these results compare with findings for whole genome intragenic regions. RESULTS: We found that GC content in coding regions is significantly higher in core genomes than accessory genomes and whole genomes. Likewise, GC content variation within coding regions was significantly lower in core genomes than in accessory genomes and whole genomes. Relative entropy in coding regions, measured as the difference between observed and expected trinucleotide frequencies estimated from mononucleotide frequencies, was significantly higher in the core genomes than in accessory and whole genomes. Relative entropy was positively associated with coding region GC content within the accessory genomes, but not within the corresponding coding regions of core or whole genomes. CONCLUSION: The higher intragenic GC content and relative entropy, as well as the lower GC content variation, observed in the core genomes is most likely associated with selective constraints. It is unclear whether the positive association between GC content and relative entropy in the more mobile accessory genomes constitutes signatures of selection or selective neutral processes.

Deep sequencing analysis of tick-borne encephalitis virus from questing ticks at natural foci reveals similarities between quasispecies pools of the virus.

Every year, tick-borne encephalitis virus (TBEV) causes severe central nervous system infection in 10 000 to 15 000 people in Europe and Asia. TBEV is maintained in the environment by an enzootic cycle that requires a tick vector and a vertebrate host, and the adaptation of TBEV to vertebrate and invertebrate environments is essential for TBEV persistence in nature. This adaptation is facilitated by the error-prone nature of the virus's RNA-dependent RNA polymerase, which generates genetically distinct virus variants called quasispecies. TBEV shows a focal geographical distribution pattern where each focus represents a TBEV hotspot. Here, we sequenced and characterized two TBEV genomes, JP-296 and JP-554, from questing Ixodes ricinus ticks at a TBEV focus in central Sweden. Phylogenetic analysis showed geographical clustering among the newly sequenced strains and three previously sequenced Scandinavian strains, Toro-2003, Saringe-2009 and Mandal-2009, which originated from the same ancestor. Among these five Scandinavian TBEV strains, only Mandal-2009 showed a large deletion within the 3' non-coding region (NCR), similar to the highly virulent TBEV strain Hypr. Deep sequencing of JP-296, JP-554 and Mandal-2009 revealed significantly high quasispecies diversity for JP-296 and JP-554, with intact 3'NCRs, compared to the low diversity in Mandal-2009, with a truncated 3'NCR. Single-nucleotide polymorphism analysis showed that 40 % of the single-nucleotide polymorphisms were common between quasispecies populations of JP-296 and JP-554, indicating a putative mechanism for how TBEV persists and is maintained within its natural foci.

Hepatitis C reinfection after sustained virological response.

BACKGROUND & AIMS: On-going risk behaviour can lead to hepatitis C virus (HCV) reinfection following successful treatment. We aimed to assess the incidence of persistent HCV reinfection in a population of people who inject drugs (PWID) who had achieved sustained virological response (SVR) seven years earlier. METHODS: In 2004-2006 we conducted a multicentre treatment trial comprising HCV genotype 2 or 3 patients in Sweden, Norway and Denmark (NORTH-C). Six months of abstinence from injecting drug use (IDU) was required before treatment. All Norwegian patients who had obtained SVR (n=161) were eligible for participation in this long-term follow-up study assessing virological and behavioural characteristics. RESULTS: Follow-up data were available in 138 of 161 (86%) individuals. Persistent reinfection was identified in 10 of 94 (11%) individuals with a history of IDU prior to treatment (incidence rate 1.7/100 person-years (PY); 95% CI 0.8-3.1) and in 10 of 37 (27%) individuals who had relapsed to IDU after treatment (incidence rate 4.9/100 PY; 95% CI 2.3-8.9). Although relapse to IDU perfectly predicted reinfection, no baseline factor was associated with reinfection. Relapse to IDU was associated with age <30 years (vs. ⩾40 years) at treatment (adjusted odds ratio [aOR] 7.03; 95% CI 1.78-27.8) and low education level (aOR 3.64; 95% CI 1.44-9.18). CONCLUSIONS: Over time, persistent HCV reinfection was common among individuals who had relapsed to IDU after treatment. Reinfection should be systematically addressed and prevented when providing HCV care for PWID.

Dating the origin of the genus Flavivirus in the light of Beringian biogeography.

The genus Flavivirus includes some of the most important human viral pathogens, and its members are found in all parts of the populated world. The temporal origin of diversification of the genus has long been debated due to the inherent problems with dating deep RNA virus evolution. A generally accepted hypothesis suggests that Flavivirus emerged within the last 10 000 years. However, it has been argued that the tick-borne Powassan flavivirus was introduced into North America some time between the opening and closing of the Beringian land bridge that connected Asia and North America 15 000-11 000 years ago, indicating an even older origin for Flavivirus. To determine the temporal origin of Flavivirus, we performed Bayesian relaxed molecular clock dating on a dataset with high coverage of the presently available Flavivirus diversity by combining tip date calibrations and internal node calibration, based on the Powassan virus and Beringian land bridge biogeographical event. Our analysis suggested that Flavivirus originated ~85 000 (64 000-110 000) or 120 000 (87 000-159 000) years ago, depending on the circumscription of the genus. This is significantly older than estimated previously. In light of our results, we propose that it is likely that modern humans came in contact with several members of the genus Flavivirus much earlier than suggested previously, and that it is possible that the spread of several flaviviruses coincided with, and was facilitated by, the migration and population expansion of modern humans out of Africa.

Study on the temporal and spatial distribution of Culex mosquitoes in Hanoi, Vietnam.

Arboviruses transmitted by mosquitoes, including Japanese encephalitis virus (JEV), present a substantial global health threat. JEV is transmitted by mosquitoes in the genus Culex, which are common in both urban and rural areas in Vietnam. In 2020, we conducted a 1-year survey of Culex mosquito abundance in urban, suburban, and peri-urban areas of Hanoi using CDC-light traps. Mosquitoes were identified to species and sorted into pools based on species, sex, and trap location. The mosquito pools were also investigated by RT-qPCR for detection of JEV. In total, 4829 mosquitoes were collected over a total of 455 trap-nights, across 13 months. Collected mosquitoes included Culex, Aedes, Anopheles, and Mansonia species. Culex mosquitoes, primarily Cx. quinquefasciatus, predominated, especially in peri-urban areas. Most Culex mosquitoes were caught in the early months of the year. The distribution and abundance of mosquitoes exhibited variations across urban, suburban, and peri-urban sites, emphasizing the influence of environmental factors such as degree of urbanization, temperature and humidity on Culex abundance. No JEV was detected in the mosquito pools. This study establishes baseline knowledge of Culex abundance and temporal variation, which is crucial for understanding the potential for JEV transmission in Hanoi.

Substantial viral and bacterial diversity at the bat-tick interface.

Ticks harbour a high diversity of viruses, bacteria and protozoa. The soft tick Carios vespertilionis (Argasidae) is a common ectoparasite of bats in the Palearctic region and is suspected to be vector and reservoir of viruses and other microbial species in bat populations, some of which may act as zoonotic agents for human disease. The Soprano pipistrelle (Pipistrellus pygmaeus, Vespertilionidae) is widely distributed in Europe, where it can be found inside or close to human habitation. We used meta-transcriptomic sequencing to determine the RNA virome and common microbiota in blood-fed C. vespertilionis ticks collected from a Soprano pipistrelle bat roosting site in south-central Sweden. Our analyses identified 16 viruses from 11 virus families, of which 15 viruses were novel. For the first time in Sweden we identified Issuk-Kul virus, a zoonotic arthropod-borne virus previously associated with outbreaks of acute febrile illness in humans. Probable bat-associated and tick-borne viruses were classified within the families Nairoviridae, Caliciviridae and Hepeviridae, while other invertebrate-associated viruses included members of the Dicistroviridae, Iflaviridae, Nodaviridae, Partitiviridae, Permutotetraviridae, Polycipiviridae and Solemoviridae. Similarly, we found abundant bacteria in C. vespertilionis, including genera with known tick-borne bacteria, such as Coxiella spp. and Rickettsia spp. These findings demonstrate the remarkable diversity of RNA viruses and bacteria present in C. vespertilionis and highlight the importance of bat-associated ectoparasite surveillance as an effective and non-invasive means to track viruses and bacteria circulating in bats and ticks.

Meta-transcriptomics reveals potential virus transfer between Aedes communis mosquitoes and their parasitic water mites.

Arthropods harbor a largely undocumented diversity of RNA viruses. Some arthropods, like mosquitoes, can transmit viruses to vertebrates but are themselves parasitized by other arthropod species, such as mites. Very little is known about the viruses of these ectoparasites and how they move through the host-parasite relationship. To address this, we determined the virome of both mosquitoes and the mites that feed on them. The mosquito Aedes communis is an abundant and widely distributed species in Sweden, in northern Europe. These dipterans are commonly parasitized by water mite larvae (Trombidiformes: Mideopsidae) that are hypothesized to impose negative selection pressures on the mosquito by reducing fitness. In turn, viruses are dual-host agents in the mosquito-mite interaction. We determined the RNA virus diversity of mite-free and mite-detached mosquitoes, as well as their parasitic mites, using meta-transcriptomic sequencing. Our results revealed an extensive RNA virus diversity in both mites and mosquitoes, including thirty-seven putative novel RNA viruses that cover a wide taxonomic range. Notably, a high proportion of viruses (20/37) were shared between mites and mosquitoes, while a limited number of viruses were present in a single host. Comparisons of virus composition and abundance suggest potential virus transfer between mosquitoes and mites during their symbiotic interaction. These findings shed light on virome diversity and ecology in the context of arthropod host-parasite-virus relationships.

Age and sex effects on DNA methylation sites linked to genes implicated in severe COVID-19 and SARS-CoV-2 host cell entry.

Male sex and advanced age are associated with severe symptoms of COVID-19. Sex and age also exhibit substantial associations with genome-wide DNA methylation (DNAm) differences in humans. Using a random sample of Illumina EPIC-based genome-wide methylomes from peripheral whole blood of 1,976 parents, participating in The Norwegian Mother, Father and Child Cohort Study (MoBa), we explored whether DNAm in genes linked to SARS-CoV-2 host cell entry and to severe COVID-19 were associated with sex and age. This was carried out by testing 1,572 DNAm sites (CpGs) located near 45 genes for associations with age and sex. We found that DNAm in 281 and 231 of 1,572 CpGs were associated (pFDR<0.01) with sex and aging, respectively. CpGs linked to SARS-CoV-2 host cell entry genes were all associated with age and sex, except for the ACE2 receptor gene (located on the X-chromosome), which was only associated with sex (pFDR<0.01). Furthermore, we examined whether 1,487 autosomal CpGs associated with host-cell entry and severe COVID-19 were more or less associated with sex and age than what would be expected from the same number of randomly sampled genome-wide CpGs. We found that the CpGs associated with host-cell entry and severe COVID-19 were not more or less associated with sex (R2 = 0.77, p = 0.09) than the CpGs sampled from random genomic regions; age was actually found to be significantly less so (R2 = 0.36, p = 0.04). Hence, while we found wide-spread associations between sex and age at CpGs linked to genes implicated with SARS-CoV-2 host cell entry and severe COVID-19, the effect from the sum of these CpGs was not stronger than that from randomly sampled CpGs; for age it was significantly less so. These findings could suggest that advanced age and male sex may not be unsurmountable barriers for the SARS-CoV-2 virus to evolve increased infectiousness.

Widespread interspecific phylogenetic tree incongruence between mosquito-borne and insect-specific flaviviruses at hotspots originally identified in Zika virus.

Intraspecies (homologous) phylogenetic incongruence, or 'tree conflict' between different loci within the same genome of mosquito-borne flaviviruses (MBFV), was first identified in dengue virus (DENV) and subsequently in Japanese encephalitis virus (JEV), St Louis encephalitis virus, and Zika virus (ZIKV). Recently, the first evidence of phylogenetic incongruence between interspecific members of the MBFV was reported in ZIKV and its close relative, Spondweni virus. Uniquely, these hybrid proteomes were derived from four incongruent trees involving an Aedes-associated DENV node (1 tree) and three different Culex-associated flavivirus nodes (3 trees). This analysis has now been extended across a wider spectrum of viruses within the MBFV lineage targeting the breakpoints between phylogenetic incongruent loci originally identified in ZIKV. Interspecies phylogenetic incongruence at these breakpoints was identified in 10 of 50 viruses within the MBFV lineage, representing emergent Aedes and Culex-associated viruses including JEV, West Nile virus, yellow fever virus, and insect-specific viruses. Thus, interspecies phylogenetic incongruence is widespread amongst the flaviviruses and is robustly associated with the specific breakpoints that coincide with the interspecific phylogenetic incongruence previously identified, inferring they are 'hotspots'. The incongruence amongst the emergent MBFV group was restricted to viruses within their respective associated epidemiological boundaries. This MBFV group was RY-coded at the third codon position ('wobble codon') to remove transition saturation. The resulting 'wobble codon' trees presented a single topology for the entire genome that lacked any robust evidence of phylogenetic incongruence between loci. Phylogenetic interspecific incongruence was therefore observed for exactly the same loci between amino acid and the RY-coded 'wobble codon' alignments and this incongruence represented either a major part, or the entire genomes. Maximum likelihood codon analysis revealed positive selection for the incongruent lineages. Positive selection could result in the same locus producing two opposing trees. These analyses for the clinically important MBFV suggest that robust interspecific phylogenetic incongruence resulted from amino acid selection. Convergent or parallel evolutions are evolutionary processes that would explain the observation, whilst interspecific recombination is unlikely.

Discovery of a Novel Coronavirus in Swedish Bank Voles (Myodes glareolus).

The unprecedented pandemic COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with bats as original reservoirs, has once again highlighted the importance of exploring the interface of wildlife diseases and human health. In this study, we identified a novel Betacoronavirus from bank voles (Myodes glareolus) in Grimsö, Sweden, and this virus is designated as Grimso virus. Repeated detection over three years and an overall prevalence of 3.4% suggest that the virus commonly occurs in bank voles. Furthermore, phylogenetic analyses indicate that the Grimso virus belongs to a highly divergent Embecovirus lineage predominantly associated with bank voles. Given that bank voles are one of the most common rodent species in Sweden and Europe, our findings indicate that Grimso virus might be circulating widely in bank voles and further point out the importance of sentinel surveillance of coronaviruses in wild small mammalian animals, especially in wild rodents.

Assessment of Coronavirus Disease 2019 Intervention Strategies in the Nordic Countries Using Genomic Epidemiology.

We explored how the duration, size, and number of virus transmission clusters, defined as country-specific monophyletic groups in a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) phylogenetic tree, differed among the Nordic countries of Norway, Sweden, Denmark, Finland, and Iceland. Our results suggest that although geographical connectivity, population density, and openness influence the spread and the size of SARS-CoV-2 transmission clusters, the different country-specific intervention strategies had the largest impact. We also found a significant positive association between the size and duration of transmission clusters in the Nordic countries, suggesting that the rapid deployment of contact tracing is a key response measure in reducing virus transmission.

Co-Occurrence of Francisella, Spotted Fever Group Rickettsia, and Midichloria in Avian-Associated Hyalomma rufipes.

The migratory behavior of wild birds contributes to the geographical spread of ticks and their microorganisms. In this study, we aimed to investigate the dispersal and co-occurrence of Francisella and spotted fever group Rickettsia (SFGR) in ticks infesting birds migrating northward in the African-Western Palaearctic region (AWPR). Birds were trapped with mist nests across the Mediterranean basin during the 2014 and 2015 spring migration. In total, 575 ticks were collected from 244 birds. We screened the ticks for the species Francisella tularensis, the genus Francisella, and SFGR by microfluidic real-time PCR. Confirmatory analyses and metagenomic sequencing were performed on tick samples that putatively tested positive for F. tularensis during initial screenings. Hyalomma rufipes was the most common tick species and had a high prevalence of Francisella, including co-occurrence of Francisella and SFGR. Metagenomic analysis of total DNA extracted from two H. rufipes confirmed the presence of Francisella, Rickettsia, and Midichloria. Average nucleotide identity and phylogenetic inference indicated the highest identity of the metagenome-assembled genomes to a Francisella-like endosymbiont (FLE), Rickettsia aeschlimannii, and Midichloria mitochondrii. The results of this study suggest that (i) FLE- and SFGR-containing ticks are dispersed by northbound migratory birds in the AWPR, (ii) H. rufipes likely is not involved in transmission of F. tularensis in the AWPR, and (iii) a dual endosymbiosis of FLEs and Midichloria may support some of the nutritional requirements of H. rufipes.