Background: Superspreading events are important drivers of the SARS-CoV-2 pandemic. By analyzing two outbreaks associated with choir rehearsals in March 2020, we demonstrate the risk of indoor, long-range (LR) transmission and singing, to help prevent similar outbreaks. 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. WGS confirmed strain identity in both choirs and the primary case of choir 1 (transmitting presymptomatically). Particle emission rate when singing was 7 times higher compared to talking. In choir 1, the median concentration of primary cases’ emitted particles was 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 (median: 89% vs. 18%, 95%CI: 80-95% vs. 6-36%). Observed AR in choir 1 (89%) was significantly higher than in choir 2 (24%). According to a risk model, first transmission in choir 1 occurred likely after 7 minutes of singing. The number of inhaled particles emitted by an infectious case, sufficient to infect 50% of exposed, was calculated to 1039-2883 particles (95%CI).Conclusions: Even in large rooms, singing of an infectious person may lead to secondary infections through LR exposure within minutes. Given the potential for presymptomatic infectiousness, greatest caution is required wherever aerosols can accumulate.

In regions lacking genomic data, analysis of sequences from the early stages of an outbreak can provide important insights into the diversity of pathogens present. Following the detection of the first imported case of COVID-19 in the Northern sector of Ghana on 13^th March 2020, we have now molecularly characterized and phylogenetically analysed sequences including three (3) complete genomes of the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) isolated from nine (9) patients observed in Ghana. Eight (8) of these patients reported with a recent history of foreign travel and one (1) with no history of foreign travel. We performed high throughput sequencing for 9 samples following the determination of high concentration of viral RNA. In addition, we estimated the potential impact that long distance transportation of samples to testing centres may have on sequencing outcomes. Here, two samples that were closest in terms of viral RNA concentration but transported from sites which are over 400km apart were assessed. All sequences were compared to previous sequences from Ghana and representative sequences from regions where our patients had previously travelled. Complete genomes were obtained for three (3) sequences and with another near complete genome with a coverage of 95.6%. Sequences with coverage in excess of 80% were found to belong to three lineages namely A, B.1 and B.2. Our sequences clustered in two different clades with the majority falling within a clade composed of sequences from sub-Saharan Africa. Less RNA fragmentation was seen in sample KATH23 which was collected 9km compared with sample TTH6 which was collected and transported over a distance of 400km to the testing site. The clustering of several sequences from sub-Saharan Africa suggests regional circulation of the viruses in the subregion. Importantly, there may be the need to decentralize testing sites and build more capacity across Africa to boost the sequencing output of the subregion.