Insights into household transmission of SARS-CoV-2 from a population-based serological survey

Understanding the risk of infection from household- and community-exposures and the transmissibility of asymptomatic infections is critical to SARS-CoV-2 control. Limited previous evidence is based primarily on virologic testing, which disproportionately misses mild and asymptomatic infections. Serologic measures are more likely to capture all previously infected individuals. We apply household transmission models to data from a cross-sectional, household-based population serosurvey of 4,534 people ≥5 years from 2,267 households enrolled April-June 2020 in Geneva, Switzerland. We found that the risk of infection from exposure to a single infected household member aged ≥5 years (17.3%,13.7-21.7) was more than three-times that of extra-household exposures over the first pandemic wave (5.1%,4.5-5.8). Young children had a lower risk of infection from household members. Working-age adults had the highest extra-household infection risk. Seropositive asymptomatic household members had 69.4% lower odds (95%CrI,31.8-88.8%) of infecting another household member compared to those reporting symptoms, accounting for 14.5% (95%CrI, 7.2-22.7%) of all household infections

New shuttle vector for cloning in Bacillus stearothermophilus

Cloning vector plasmid pRP9 was constructed on the basis of the broad host-range plasmid pLM6. pRP9 was a small plasmid (2.9 kb), possessed a convenient polyrestriction site sequence and efficiently transformed Bacillus subtilis, Bacillus stearothermophilus and Escherichia coli. Furthermore, pRP9 presented a very high segregational stability in Bacillus hosts. Also, the structural stability in Bacillus strains, grown under selective pressure, of pRP9 carrying a 3-kb fragment, was high. No single-stranded and high-molecular weight pRP9 DNA was found in B. stearothermophilus. The host/vector systems described possessed all the properties required for efficient gene cloning