Unexpected differences in the population genetics of phasmavirids (Bunyavirales) from subarctic ponds

Crimean-Congo Hemorrhagic Fever, Spain, 2013-2021

Crimean-Congo hemorrhagic fever (CCHF) is a viral infectious disease for which distribution of the main vector, Hyalomma spp. ticks, is expanding. We analyzed all 10 cases of CCHF diagnosed in Spain during 2013-2021; case-patient median age was 56.5 years, and 7 were men. We identified CCHF virus genotypes III and V. Six case-patients acquired the infection in urban areas. Sixty percent of patients were infected in summer and 40% in spring. Two patients met criteria for hemophagocytic syndrome. Seven patients survived. The epidemiologic pattern of CCHF in Spain is based on occasional cases with an elevated mortality rate. Genotype III and, to a less extent also genotype V, CCHF circulates in humans in a common geographic area in Spain. Those data suggest that the expansion pathways are complex and may change over time. Physicians should remain alert to the possibility of new CCHF cases.

Crimean-Congo haemorrhagic fever (CCHF) virus-specific antibody detection in blood donors, Castile-León, Spain, summer 2017 and 2018

BackgroundCrimean-Congo haemorrhagic fever virus (CCHFV) is considered an emerging or even a probable re-emerging pathogen in southern Europe. Presence of this virus had been reported previously in Spain in 2010.AimWe aimed to evaluate the potential circulation of CCHFV in western Spain with a serosurvey in asymptomatic adults (blood donors).MethodsDuring 2017 and 2018, we conducted a CCHFV serosurvey in randomly selected asymptomatic blood donors from western Spain. Three assays using specific IgG antibodies against CCHFV were performed: the VectoCrimea ELISA test, an in-house ELISA and indirect immunofluorescence (EuroImmun) test with glycoprotein and nucleoprotein.ResultsA total of 516 blood donors participated in this cross-sectional study. The majority of the study participants were male (68.4%), and the mean age was 46.3 years. Most of the participants came from rural areas (86.8%) and 68.6% had contact with animals and 20.9% had animal husbandry practices. One in five participants (109/516, 21.1%) were engaged in at-risk professional activities such as agriculture and shepherding, slaughtering, hunting, veterinary and healthcare work (mainly nursing staff and laboratory technicians). A total of 15.3% of the participants were bitten by ticks in the days or months before the date of sampling. We detected anti-CCHFV IgG antibodies with two diagnostic assays in three of the 516 individuals and with one diagnostic assay in six of the 516 individuals.ConclusionSeroprevalence of CCHFV was between 0.58% and 1.16% in Castile-León, Spain. This is the first study in western Spain that showed circulation of CCHFV in healthy people.

Evolutionary persistence of insect bunyavirus infection despite host acquisition and expression of the viral nucleoprotein gene

How insects combat RNA virus infection is a subject of intensive research owing to its importance in insect health, virus evolution, and disease transmission. In recent years, a pair of potentially linked phenomena have come to light as a result of this work-first, the pervasive production of viral DNA from exogenous nonretroviral RNA in infected individuals, and second, the widespread distribution of nonretroviral integrated RNA virus sequences (NIRVs) in the genomes of diverse eukaryotes. The evolutionary consequences of NIRVs for viruses are unclear and the field would benefit from studies of natural virus infections co-occurring with recent integrations, an exceedingly rare circumstance in the literature. Here, we provide evidence that a novel insect-infecting phasmavirus (Order Bunyavirales) has been persisting in a phantom midge host, Chaoborus americanus, for millions of years. Interestingly, the infection persists despite the host's acquisition (during the Pliocene), fixation, and expression of the viral nucleoprotein gene. We show that virus prevalence and geographic distribution are high and broad, comparable to the host-specific infections reported in other phantom midges. Short-read mapping analyses identified a lower abundance of the nucleoprotein-encoding genome segment in this virus relative to related viruses. Finally, the novel virus has facilitated the first substitution rate estimation for insect-infecting phasmaviruses. Over a period of approximately 16 million years, we find rates of (0.6 - 1.6) × 10^-7 substitutions per site per year in protein coding genes, extraordinarily low for negative-sense RNA viruses, but consistent with the few estimates produced over comparable evolutionary timescales.

Bunyavirales ribonucleoproteins: the viral replication and transcription machinery

The Bunyavirales order is one of the largest groups of segmented negative-sense single-stranded RNA viruses, which includes many pathogenic strains that cause severe human diseases. The RNA segments of the bunyavirus genome are separately encapsidated by multiple copies of nucleoprotein (N), and both termini of each N-encapsidated genomic RNA segment bind to one copy of the viral L polymerase protein. The viral genomic RNA, N and L protein together form the ribonucleoprotein (RNP) complex that constitutes the molecular machinery for viral genome replication and transcription. Recently, breakthroughs have been achieved in understanding the architecture of bunyavirus RNPs with the determination of the atomic structures of the N and L proteins from various members of this order. In this review, we discuss the structures and functions of these bunyavirus RNP components, as well as viral genome replication and transcription mechanisms.