RESUMEN
The mpox virus (MPXV) is mutating at an exceptional rate for a DNA virus and its global spread is concerning, making genomic surveillance a necessity. With MpoxRadar, we provide an interactive dashboard to track virus variants on mutation level worldwide. MpoxRadar allows users to select among different genomes as reference for comparison. The occurrence of mutation profiles based on the selected reference is indicated on an interactive world map that shows the respective geographic sampling site in customizable time ranges to easily follow the frequency or trend of defined mutations. Furthermore, the user can filter for specific mutations, genes, countries, genome types, and sequencing protocols and download the filtered data directly from MpoxRadar. On the server, we automatically download all MPXV genomes and metadata from the National Center for Biotechnology Information (NCBI) on a daily basis, align them to the different reference genomes, generate mutation profiles, which are stored and linked to the available metainformation in a database. This makes MpoxRadar a practical tool for the genomic survaillance of MPXV, supporting users with limited computational resources. MpoxRadar is open-source and freely accessible at https://MpoxRadar.net.
Asunto(s)
Genoma Viral , Genómica , Monkeypox virus , Programas Informáticos , Bases de Datos Factuales , Monkeypox virus/genéticaRESUMEN
In July 2023, clade IIb-associated mpox reemerged in Germany at low levels, mainly affecting men who have sex with men. We report a representative case and phylogeny of available genome sequences. Our findings underscore the need for standardized surveillance and indication-based vaccination to limit transmission and help prevent endemicity.
Asunto(s)
Filogenia , Alemania/epidemiología , Humanos , Masculino , Enfermedades Transmisibles Emergentes/epidemiología , Persona de Mediana Edad , Homosexualidad Masculina , Adulto , FemeninoRESUMEN
PURPOSE: COViK, a prospective hospital-based multicenter case-control study in Germany, aims to assess the effectiveness of COVID-19 vaccines against severe disease. Here, we report vaccine effectiveness (VE) against COVID-19-caused hospitalization and intensive care treatment during the Omicron wave. METHODS: We analyzed data from 276 cases with COVID-19 and 494 control patients recruited in 13 hospitals from 1 December 2021 to 5 September 2022. We calculated crude and confounder-adjusted VE estimates. RESULTS: 21% of cases (57/276) were not vaccinated, compared to 5% of controls (26/494; p < 0.001). Confounder-adjusted VE against COVID-19-caused hospitalization was 55.4% (95% CI: 12-78%), 81.5% (95% CI: 68-90%) and 95.6% (95%CI: 88-99%) after two, three and four vaccine doses, respectively. VE against hospitalization due to COVID-19 remained stable up to one year after three vaccine doses. CONCLUSION: Three vaccine doses remained highly effective in preventing severe disease and this protection was sustained; a fourth dose further increased protection.
Asunto(s)
COVID-19 , Humanos , COVID-19/epidemiología , COVID-19/prevención & control , Vacunas contra la COVID-19 , Estudios de Casos y Controles , Estudios Prospectivos , Eficacia de las Vacunas , Alemania/epidemiologíaRESUMEN
Poxviruses are known to evolve slower than RNA viruses with only 1-2 mutations/genome/year. Rather than single mutations, rearrangements such as gene gain and loss, which have been discussed as a possible driver for host adaption, were described in poxviruses. In 2022 and 2023 the world is being challenged by the largest global outbreak so far of Mpox virus, and the virus seems to have established itself in the human community for an extended period of time. Here, we report five Mpox virus genomes from Germany with extensive gene duplication and loss, leading to the expansion of the ITR regions from 6400 to up to 24,600 bp. We describe duplications of up to 18,200 bp to the opposed genome end, and deletions at the site of insertion of up to 16,900 bp. Deletions and duplications of genes with functions of supposed immune modulation, virulence and host adaption as B19R, B21R, B22R and D10L are described. In summary, we highlight the need for monitoring rearrangements of the Mpox virus genome rather than for monitoring single mutations only.
Asunto(s)
Mpox , Poxviridae , Humanos , Duplicación de Gen , Mpox/genética , Genoma Viral/genética , Poxviridae/genética , MutaciónRESUMEN
BACKGROUND: Comprehensive pathogen genomic surveillance represents a powerful tool to complement and advance precision vaccinology. The emergence of the Alpha variant in December 2020 and the resulting efforts to track the spread of this and other severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern led to an expansion of genomic sequencing activities in Germany. METHODS: At Robert Koch Institute (RKI), the German National Institute of Public Health, we established the Integrated Molecular Surveillance for SARS-CoV-2 (IMS-SC2) network to perform SARS-CoV-2 genomic surveillance at the national scale, SARS-CoV-2-positive samples from laboratories distributed across Germany regularly undergo whole-genome sequencing at RKI. RESULTS: We report analyses of 3623 SARS-CoV-2 genomes collected between December 2020 and December 2021, of which 3282 were randomly sampled. All variants of concern were identified in the sequenced sample set, at ratios equivalent to those in the 100-fold larger German GISAID sequence dataset from the same time period. Phylogenetic analysis confirmed variant assignments. Multiple mutations of concern emerged during the observation period. To model vaccine effectiveness in vitro, we employed authentic-virus neutralization assays, confirming that both the Beta and Zeta variants are capable of immune evasion. The IMS-SC2 sequence dataset facilitated an estimate of the SARS-CoV-2 incidence based on genetic evolution rates. Together with modeled vaccine efficacies, Delta-specific incidence estimation indicated that the German vaccination campaign contributed substantially to a deceleration of the nascent German Delta wave. CONCLUSIONS: SARS-CoV-2 molecular and genomic surveillance may inform public health policies including vaccination strategies and enable a proactive approach to controlling coronavirus disease 2019 spread as the virus evolves.
Asunto(s)
COVID-19 , SARS-CoV-2 , COVID-19/epidemiología , COVID-19/prevención & control , Genoma Viral , Genómica , Humanos , Filogenia , SARS-CoV-2/genética , VacunologíaRESUMEN
Before the international spread of monkeypox in May 2022, PCR kits for the detection of orthopoxviruses, and specifically monkeypox virus, were rarely available. Here we describe the evaluation of 11 recently developed commercially available PCR kits for the detection of monkeypox virus DNA. All tested kits are currently intended for research use only and clinical performance still needs to be assessed in more detail, but all were suitable for diagnostics of monkeypox virus, with variations in specificity rather than sensitivity.
Asunto(s)
Mpox , Humanos , Mpox/diagnóstico , Mpox/epidemiología , Monkeypox virus/genética , Berlin , ADN Viral/genética , ADN Viral/análisis , Reacción en Cadena de la PolimerasaRESUMEN
BACKGROUND: The reliable detection of SARS-CoV-2 has become one of the most important contributions to COVID-19 crisis management. With the publication of the first sequences of SARS-CoV-2, several diagnostic PCR assays have been developed and published. In addition to in-house assays the market was flooded with numerous commercially available ready-to-use PCR kits, with both approaches showing alarming shortages in reagent supply. AIM: Here we present a resource-efficient in-house protocol for the PCR detection of SARS-CoV-2 RNA in patient specimens (RKI/ZBS1 SARS-CoV-2 protocol). METHODS: Two duplex one-step real-time RT-PCR assays are run simultaneously and provide information on two different SARS-CoV-2 genomic regions. Each one is duplexed with a control that either indicates potential PCR inhibition or proves the successful extraction of nucleic acid from the clinical specimen. RESULTS: Limit of RNA detection for both SARS-CoV-2 assays is below 10 genomes per reaction. The protocol enables testing specimens in duplicate across the two different SARS-CoV-2 PCR assays, saving reagents by increasing testing capacity. The protocol can be run on various PCR cyclers with several PCR master mix kits. CONCLUSION: The presented RKI/ZBS1 SARS-CoV-2 protocol represents a cost-effective alternative in times of shortages when commercially available ready-to-use kits may not be available or affordable.
Asunto(s)
Prueba de Ácido Nucleico para COVID-19/métodos , COVID-19/diagnóstico , ARN Viral/análisis , Reacción en Cadena en Tiempo Real de la Polimerasa/métodos , SARS-CoV-2/genética , Proteínas de la Envoltura de Coronavirus/genética , Secuenciación de Nucleótidos de Alto Rendimiento/métodos , Humanos , Límite de Detección , Poliproteínas/genética , ARN Viral/genética , SARS-CoV-2/aislamiento & purificación , Sensibilidad y Especificidad , Proteínas Virales/genéticaRESUMEN
Point of care detection of SARS-CoV-2 is one pillar in a containment strategy and important to break infection chains. Here we report the sensitive, specific and robust detection of SARS-CoV-2 and respective variants of concern by the ID NOW COVID-19 device.
Asunto(s)
Prueba de COVID-19/métodos , COVID-19/diagnóstico , Técnicas de Diagnóstico Molecular/métodos , Sistemas de Atención de Punto , SARS-CoV-2/genética , COVID-19/virología , Técnicas de Laboratorio Clínico/métodos , Humanos , Reproducibilidad de los Resultados , SARS-CoV-2/fisiología , Sensibilidad y EspecificidadRESUMEN
Quality management and independent assessment of high-throughput sequencing-based virus diagnostics have not yet been established as a mandatory approach for ensuring comparable results. The sensitivity and specificity of viral high-throughput sequence data analysis are highly affected by bioinformatics processing using publicly available and custom tools and databases and thus differ widely between individuals and institutions. Here we present the results of the COMPARE [Collaborative Management Platform for Detection and Analyses of (Re-)emerging and Foodborne Outbreaks in Europe] in silico virus proficiency test. An artificial, simulated in silico data set of Illumina HiSeq sequences was provided to 13 different European institutes for bioinformatics analysis to identify viral pathogens in high-throughput sequence data. Comparison of the participants' analyses shows that the use of different tools, programs, and databases for bioinformatics analyses can impact the correct identification of viral sequences from a simple data set. The identification of slightly mutated and highly divergent virus genomes has been shown to be most challenging. Furthermore, the interpretation of the results, together with a fictitious case report, by the participants showed that in addition to the bioinformatics analysis, the virological evaluation of the results can be important in clinical settings. External quality assessment and proficiency testing should become an important part of validating high-throughput sequencing-based virus diagnostics and could improve the harmonization, comparability, and reproducibility of results. There is a need for the establishment of international proficiency testing, like that established for conventional laboratory tests such as PCR, for bioinformatics pipelines and the interpretation of such results.
Asunto(s)
Biología Computacional/métodos , Simulación por Computador , Secuenciación de Nucleótidos de Alto Rendimiento/normas , Ensayos de Aptitud de Laboratorios/estadística & datos numéricos , Análisis de Secuencia de ADN/normas , Virus/genética , Análisis de Datos , Europa (Continente) , Genoma Viral , Secuenciación de Nucleótidos de Alto Rendimiento/métodos , Humanos , Colaboración Intersectorial , Ensayos de Aptitud de Laboratorios/organización & administración , Reproducibilidad de los Resultados , Análisis de Secuencia de ADN/estadística & datos numéricos , Virus/patogenicidadRESUMEN
Next-generation sequencing technologies have significantly facilitated the discovery of novel viruses, and metagenomic surveillance of arthropods has enabled exploration of the diversity of novel or known viral agents. We have identified a novel rhabdovirus that is genetically related to the recently described Merida virus via next-generation sequencing in a mosquito pool from Thrace. The complete viral genome contains 11,798 nucleotides with 83% genome-wide nucleotide sequence similarity to Merida virus. Five major putative open reading frames that follow the canonical rhabdovirus genome organization were identified. A total of 1380 mosquitoes comprising 13 species, collected from Thrace and the Mediterranean and Aegean regions of Anatolia were screened for the novel virus using primers based on the N and L genes of the prototype genome. Eight positive pools (6.2%) exclusively comprised Culex pipiens sensu lato specimens originating from all study regions. Infections were observed in pools with female as well as male or mixed-sex individuals. The overall and Cx. pipiens-specific minimal infection rates were calculated to be 5.7 and 14.8, respectively. Sequencing of the PCR products revealed marked diversity within a portion of the N gene, with up to 4% divergence and distinct amino acid substitutions that were unrelated to the collection site. Phylogenetic analysis of the complete and partial viral polymerase (L gene) amino acid sequences placed the novel virus and Merida virus in a distinct group, indicating that these strains are closely related. The strain is tentatively named "Merida-like virus Turkey". Studies are underway to isolate and further explore the host range and distribution of this new strain.
Asunto(s)
Culicidae/virología , Rhabdoviridae/genética , Rhabdoviridae/aislamiento & purificación , Animales , Femenino , Genoma Viral , Masculino , Filogenia , Turquía/epidemiologíaRESUMEN
Surveillance and monitoring of viral pathogens circulating in humans and wildlife, together with the identification of emerging infectious diseases (EIDs), are critical for the prediction of future disease outbreaks and epidemics at an early stage. It is advisable to sample a broad range of vertebrates and invertebrates at different temporospatial levels on a regular basis to detect possible candidate viruses at their natural source. However, virus surveillance systems can be expensive, costly in terms of finances and resources and inadequate for sampling sufficient numbers of different host species over space and time. Recent publications have presented the concept of a new virus surveillance system, coining the terms "flying biological syringes", "xenosurveillance" and "vector-enabled metagenomics". According to these novel and promising surveillance approaches, viral metagenomics on engorged mosquitoes might reflect the viral diversity of numerous mammals, birds and humans, combined in the mosquitoes' blood meal during feeding on the host. In this review article, we summarize the literature on vector-enabled metagenomics (VEM) techniques and its application in disease surveillance in humans. Furthermore, we highlight the combination of VEM and "invertebrate-derived DNA" (iDNA) analysis to identify the host DNA within the mosquito midgut.
Asunto(s)
Enfermedades Transmisibles Emergentes/epidemiología , Monitoreo Epidemiológico , Genoma Viral , Metagenómica/métodos , Virosis/epidemiología , Virus/genética , Animales , Vectores Artrópodos/virología , Aves/virología , Ceratopogonidae/virología , Enfermedades Transmisibles Emergentes/transmisión , Culicidae/virología , Dípteros/virología , Phthiraptera/virología , Roedores/virología , Siphonaptera/virología , Garrapatas/virología , Virosis/transmisión , Virus/clasificación , Virus/aislamiento & purificaciónRESUMEN
Sixty percent of emerging viruses have a zoonotic origin, making transmission from animals a major threat to public health. Prompt identification and analysis of these pathogens are indispensable to taking action toward prevention and protection of the affected population. We quantifiably compared classical and modern approaches of virus purification and enrichment in theory and experiments. Eventually, we established an unbiased protocol for detection of known and novel emerging viruses from organ tissues (tissue-based universal virus detection for viral metagenomics [TUViD-VM]). The final TUViD-VM protocol was extensively validated by using real-time PCR and next-generation sequencing. We could increase the amount of detectable virus nucleic acids and improved the detection of viruses <75,000-fold compared with other tested approaches. This TUViD-VM protocol can be used in metagenomic and virome studies to increase the likelihood of detecting viruses from any biological source.
Asunto(s)
Secuenciación de Nucleótidos de Alto Rendimiento , Técnicas de Diagnóstico Molecular , Virosis/diagnóstico , Animales , Callithrix , Embrión de Pollo , ADN Viral/genética , ADN Viral/aislamiento & purificación , Genes Virales , Humanos , Metagenoma , Reacción en Cadena en Tiempo Real de la Polimerasa , Relación Señal-Ruido , ZoonosisRESUMEN
Modified vaccinia virus Ankara (MVA) has been widely tested in clinical trials as recombinant vector vaccine against infectious diseases and cancers in humans and animals. However, one biosafety concern about the use of MVA vectored vaccine is the potential for MVA to recombine with naturally occurring orthopoxviruses in cells and hosts in which it multiplies poorly and, therefore, producing viruses with mosaic genomes with altered genetic and phenotypic properties. We previously conducted co-infection and superinfection experiments with MVA vectored influenza vaccine (MVA-HANP) and a feline Cowpox virus (CPXV-No-F1) in Vero cells (that were semi-permissive to MVA infection) and showed that recombination occurred in both co-infected and superinfected cells. In this study, we selected the putative recombinant viruses and performed genomic characterization of these viruses. Some putative recombinant viruses displayed plaque morphology distinct of that of the parental viruses. Our analysis demonstrated that they had mosaic genomes of different lengths. The recombinant viruses, with a genome more similar to MVA-HANP (>50%), rescued deleted and/or fragmented genes in MVA and gained new host ranges genes. Our analysis also revealed that some MVA-HANP contained a partially deleted transgene expression cassette and one recombinant virus contained part of the transgene expression cassette similar to that incomplete MVA-HANP. The recombination in co-infected and superinfected Vero cells resulted in recombinant viruses with unpredictable biological and genetic properties as well as recovery of delete/fragmented genes in MVA and transfer of the transgene into replication competent CPXV. These results are relevant to hazard characterization and risk assessment of MVA vectored biologicals.
Asunto(s)
Coinfección , Vacunas contra la Influenza , Sobreinfección , Chlorocebus aethiops , Animales , Gatos , Humanos , Vacunas contra la Influenza/genética , Virus de la Viruela Vacuna/genética , Células Vero , Virus Vaccinia , Vacunas Sintéticas/genética , Secuenciación Completa del GenomaRESUMEN
We present an amplicon-based assay for MinION Nanopore sequencing of mpox virus (MPXV) genomes from clinical specimens, obtaining high-quality results with an average genome coverage of 99% for Ct values of up to 25, and a genome coverage of 97.1% for Ct values from 25 to 30 which are challenging to sequence. This assay is easy to implement in PCR-based workflows and provides accurate genomic data within a short time.
Asunto(s)
Secuenciación de Nanoporos , Nanoporos , Monkeypox virus , Genómica , Secuenciación de Nucleótidos de Alto Rendimiento/métodosRESUMEN
IMPORTANCE: Modern smallpox vaccines, such as those used against mpox, are made from vaccinia viruses, but it is still unknown whether cowpox, horsepox, or vaccinia viruses were used in the early 20th century or earlier. The mystery began to be solved when the genomes of six historical smallpox vaccines used in the United States from 1850 to 1902 were determined. Our work analyzed in detail the genomes of these six historical vaccines, revealing a complex genomic structure. Historical vaccines are highly similar to horsepox in the core of their genomes, but some are closer to the structure of vaccinia virus at the ends of the genome. One of the vaccines is a recombinant virus with parts of variola virus recombined into its genome. Our data add valuable information for understanding the evolutionary path of current smallpox vaccines and the genetic makeup of the potentially extinct group of horsepox viruses.
Asunto(s)
Orthopoxvirus , Vacuna contra Viruela , Viruela , Virus de la Viruela , Humanos , Virus de la Viruela/genética , Viruela/prevención & control , Duplicación de Gen , Vacuna contra Viruela/genética , Virus Vaccinia/genética , Orthopoxvirus/genética , Recombinación GenéticaRESUMEN
We included 852 patients in a prospectively recruiting multicenter matched case-control study in Germany to assess vaccine effectiveness (VE) in preventing COVID-19-associated hospitalization during the Delta-variant dominance. The two-dose VE was 89 % (95 % CI 84-93 %) overall, 79 % in patients with more than two comorbidities and 77 % in adults aged 60-75 years. A third dose increased the VE to more than 93 % in all patient-subgroups.
Asunto(s)
COVID-19 , Vacunas , Adulto , Humanos , Estudios de Casos y Controles , COVID-19/prevención & control , Hospitalización , Hospitales , Alemania/epidemiologíaRESUMEN
Cowpox virus (CPXV; genus Orthopoxvirus; family Poxviridae) is the causative agent of cowpox, a self-limiting zoonotic infection. CPXV is endemic in Eurasia, and human CPXV infections are associated with exposure to infected animals. In the Fennoscandian region, five CPXVs isolated from cats and humans were collected and used in this study. We report the complete sequence of their genomes, which ranged in size from 220-222 kbp, containing between 215 and 219 open reading frames. The phylogenetic analysis of 87 orthopoxvirus strains, including the Fennoscandian CPXV isolates, confirmed the division of CPXV strains into at least five distinct major clusters (CPXV-like 1, CPXV-like 2, VACV-like, VARV-like and ECTV-Abatino-like) and can be further divided into eighteen sub-species based on the genetic and patristic distances. Bayesian time-scaled evolutionary history of CPXV was reconstructed employing concatenated 62 non-recombinant conserved genes of 55 CPXV. The CPXV evolution rate was calculated to be 1.65 × 10-5 substitution/site/year. Our findings confirmed that CPXV is not a single species but a polyphyletic assemblage of several species and thus, a reclassification is warranted.
Asunto(s)
Viruela Vacuna , Orthopoxvirus , Animales , Humanos , Virus de la Viruela Vacuna , Filogenia , Teorema de Bayes , Viruela Vacuna/veterinaria , Orthopoxvirus/genética , GenómicaRESUMEN
Orthopoxviruses (OPXVs) not only infect their natural hosts, but some OPXVs can also cause disease in humans. Previously, we partially characterized an OPXV isolated from an 18-year-old male living in Northern Norway. Restriction enzyme analysis and partial genome sequencing characterized this virus as an atypical cowpox virus (CPXV), which we named CPXV-No-H2. In this study, we determined the complete genome sequence of CPXV-No-H2 using Illumina and Nanopore sequencing. Our results showed that the whole CPXV-No-H2 genome is 220,276 base pairs (bp) in length, with inverted terminal repeat regions of approximately 7 kbp, containing 217 predicted genes. Seventeen predicted CPXV-No-H2 proteins were most similar to OPXV proteins from the Old World, including Ectromelia virus (ECTV) and Vaccinia virus, and North America, Alaskapox virus (AKPV). CPXV-No-H2 has a mosaic genome with genes most similar to other OPXV genes, and seven potential recombination events were identified. The phylogenetic analysis showed that CPXV-No-H2 formed a separate clade with the German CPXV isolates CPXV_GerMygEK938_17 and CPXV_Ger2010_MKY, sharing 96.4 and 96.3% nucleotide identity, respectively, and this clade clustered closely with the ECTV-OPXV Abatino clade. CPXV-No-H2 is a mosaic virus that may have arisen out of several recombination events between OPXVs, and its phylogenetic clustering suggests that ECTV-Abatino-like cowpox viruses form a distinct, new clade of cowpox viruses.
RESUMEN
Since December 2019 the world has been facing the outbreak of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Identification of infected patients and discrimination from other respiratory infections have so far been accomplished by using highly specific real-time PCRs. Here we present a rapid multiplex approach (RespiCoV), combining highly multiplexed PCRs and MinION sequencing suitable for the simultaneous screening for 41 viral and five bacterial agents related to respiratory tract infections, including the human coronaviruses NL63, HKU1, OC43, 229E, Middle East respiratory syndrome coronavirus, SARS-CoV, and SARS-CoV-2. RespiCoV was applied to 150 patient samples with suspected SARS-CoV-2 infection and compared with specific real-time PCR. Additionally, several respiratory tract pathogens were identified in samples tested positive or negative for SARS-CoV-2. Finally, RespiCoV was experimentally compared to the commercial RespiFinder 2SMART multiplex screening assay (PathoFinder, The Netherlands).
Asunto(s)
Bacterias/genética , COVID-19/diagnóstico , Secuenciación de Nucleótidos de Alto Rendimiento/métodos , Virus ARN/genética , Infecciones del Sistema Respiratorio/diagnóstico , SARS-CoV-2/genética , Bacterias/aislamiento & purificación , COVID-19/virología , Coronavirus/genética , Coronavirus/aislamiento & purificación , ADN Bacteriano/química , ADN Bacteriano/metabolismo , Herpesvirus Humano 1/genética , Herpesvirus Humano 1/aislamiento & purificación , Humanos , Reacción en Cadena de la Polimerasa Multiplex , Nanoporos , Orthomyxoviridae/genética , Orthomyxoviridae/aislamiento & purificación , Virus ARN/aislamiento & purificación , ARN Viral/química , ARN Viral/metabolismo , Infecciones del Sistema Respiratorio/microbiología , Infecciones del Sistema Respiratorio/virología , SARS-CoV-2/aislamiento & purificaciónRESUMEN
BACKGROUND: Superspreading events are important drivers of the SARS-CoV-2 pandemic and long-range (LR) transmission is believed to play a major role. We investigated two choir outbreaks with different attack rates (AR) to analyze the contribution of LR transmission and highlight important measures for prevention. METHODS: We conducted two retrospective cohort studies and obtained demographic, clinical, laboratory and contact data, performed SARS-CoV-2 serology, whole genome sequencing (WGS), calculated LR transmission probabilities, measured particle emissions of selected choir members, and calculated particle air concentrations and inhalation doses. RESULTS: We included 65 (84%) and 42 (100%) members of choirs 1 and 2, respectively, of whom 58 (89%) and 10 (24%) became cases. WGS confirmed strain identity in both choirs. Both primary cases transmitted presymptomatically. Particle emission rate when singing was 7 times higher compared to talking. In choir 1, the median concentration of primary cases' emitted particles in the room was estimated to be 8 times higher, exposure at least 30 minutes longer and room volume smaller than in choir 2, resulting in markedly different estimated probabilities for LR transmission (mode: 90% vs. 16%, 95% CI: 80-95% vs. 6-36%). According to a risk model, the first transmission in choir 1 occurred likely after 8 minutes of singing. CONCLUSIONS: The attack rate of the two choirs differed significantly reflecting the differences in LR transmission risks. The pooled proportion of cases due to LR transmission was substantial (81%; 55/68 cases) and was facilitated by likely highly infectious primary cases, high particle emission rates, and indoor rehearsing for an extended time. Even in large rooms, singing of an infectious person may lead to secondary infections through LR exposure within minutes. In the context of indoor gatherings without mask-wearing and waning or insufficient immunity, these results highlight the ongoing importance of non-pharmaceutical interventions wherever aerosols can accumulate.