A major limitation for better understanding the role of the human gut virome in health and disease is the lack of validated methods that allow high throughput virome analysis. To overcome this, we evaluated the quantitative effect of homogenisation, centrifugation, filtration, chloroform treatment and random amplification on a mock-virome (containing nine highly diverse viruses) and a bacterial mock-community (containing four faecal bacterial species) using quantitative PCR and next-generation sequencing. This resulted in an optimised protocol that was able to recover all viruses present in the mock-virome and strongly alters the ratio of viral versus bacterial and 16S rRNA genetic material in favour of viruses (from 43.2% to 96.7% viral reads and from 47.6% to 0.19% bacterial reads). Furthermore, our study indicated that most of the currently used virome protocols, using small filter pores and/or stringent centrifugation conditions may have largely overlooked large viruses present in viromes. We propose NetoVIR (Novel enrichment technique of VIRomes), which allows for a fast, reproducible and high throughput sample preparation for viral metagenomics studies, introducing minimal bias. This procedure is optimised mainly for faecal samples, but with appropriate concentration steps can also be used for other sample types with lower initial viral loads.

Rotaviruses (RVs) are responsible for more than 600,000 child deaths each year. The worldwide introduction of two life oral vaccines RotaTeq and Rotarix is believed to reduce this number significantly. Before the licensing of both vaccines, two new genotypes, G9 and G12, emerged in the human population and were able to spread across the entire globe in a very short time span. To quantify the VP7 mutation rates of these G9 and G12 genotypes and to estimate their most recent common ancestors, we used a Bayesian Markov chain Monte Carlo framework. Based on 356 sequences for G9 and 140 sequences for G12, we estimated mutation rates (nt substitutions/site/year) of 1.87 × 10(-3) (1.45-2.27 × 10(-3)) for G9 and 1.66 × 10(-3) (1.13-2.32 × 10(-3)) for G12. For both the G9 and G12 strains, one particular (sub) lineage was able to disseminate and cause disease across the world. The most recent common ancestors of these particular lineages were dated back to 1989 (1986-1992) and 1995 (1992-1998) for the G9 and G12 genotypes, respectively. These estimates suggest that a single novel RV (e.g., a vaccine escape mutant) can spread worldwide in little more than a decade. These results re-emphasize the need for thorough and continued RV surveillance in order to detect such potential spreading events at an early stage.

The COVID-19 pandemic caused by the novel coronavirus SARS-CoV-2 has spread globally, with >52,000 cases in California as of May 4, 2020. Here we investigate the genomic epidemiology of SARS-CoV-2 in Northern California from late January to mid-March 2020, using samples from 36 patients spanning 9 counties and the Grand Princess cruise ship. Phylogenetic analyses revealed the cryptic introduction of at least 7 different SARS-CoV-2 lineages into California, including epidemic WA1 strains associated with Washington State, with lack of a predominant lineage and limited transmission between communities. Lineages associated with outbreak clusters in 2 counties were defined by a single base substitution in the viral genome. These findings support contact tracing, social distancing, and travel restrictions to contain SARS-CoV-2 spread in California and other states.