Molecular epidemiology in the HIV and SARS-CoV-2 pandemics

Identifying SNP threshold from P2 sequences for investigating norovirus transmission

Noroviruses are a group of non-enveloped single-stranded positive-sense RNA virus belonging to Caliciviridae family. They can be transmitted by the fecal-oral route from contaminated food and water and cause mainly acute gastroenteritis. Outbreaks of norovirus infections could be difficult to detect and investigate. In this study, we developed a simple threshold detection approach based on variations of the P2 domain of the capsid protein. We obtained sequences from the norovirus hypervariable P2 region using Sanger sequencing, including 582 pairs of epidemiologically-related strains from 35 norovirus outbreaks and 6402 pairs of epidemiologically-unrelated strains during the four epidemic seasons. Genetic distances were calculated and a threshold was performed by adopting ROC (Receiver Operating Characteristic) curve which identified transmission clusters in all tested outbreaks with 80 % sensitivity. In average, nucleotide diversity between outbreaks was 67.5 times greater than the diversity within outbreaks. Simple and accurate thresholds for detecting norovirus transmissions of three genotypes obtained here streamlines molecular investigation of norovirus outbreaks, thus enabling rapid and efficient responses for the control of norovirus.

Direct whole-genome sequencing of HIV-1 for clinical drug-resistance analysis and public health surveillance

BACKGROUND

Human Immunodeficiency virus type 1 (HIV-1) remains a significant global health threat partly due to its ability to develop resistance to anti-retroviral therapies. HIV-1 genotype and drug resistance analysis of the polymerase (pol) sequence is a mainstay of its clinical and public health management. However, as new treatments and resistances evolve, analysis methods must change accordingly. In this study, we outline the development and implementation of a direct whole-genome sequencing approach (dWGS) using probe-capture target-enrichment for HIV-1 genotype and drug resistance analysis.

METHODS

We implemented dWGS and performed parallel pol Sanger sequencing for clinical samples, followed by comparative genotype and drug-resistance analysis. These HIV-1 WGS sequences were also utilised for a novel partitioned phylogenetic analysis.

RESULTS

Optimised nucleic acid extraction and DNAse I treatment significantly increased HIV-1 whole-genome coverage and depth, and improved recovery of high-quality genomes from low viral load clinical samples, enabling routine sequencing of viral loads as low as 1000 copies/mL. Overall, dWGS was robust, accurate and more sensitive for detecting low-frequency variants at drug-resistance sites compared to Sanger sequencing. Analysis of multiple sequence regions improved phylogenetic reconstruction for recombinant HIV-1 sequences compared to analysis of pol sequence alone.

CONCLUSIONS

These findings demonstrate dWGS enhances HIV-1 drug-resistance analysis by quantitative variant detection and improves reconstruction of HIV-1 phylogenies compared to traditional pol sequencing. This work supports that HIV-1 dWGS is a viable option to replace Sanger sequencing for clinical and public health applications.

Using molecular methods to delineate norovirus outbreaks: a systematic review

Noroviruses are among the major causative agents of human acute gastroenteritis, and the nature of norovirus outbreaks can differ considerably. The number of single-nucleotide polymorphisms (SNPs) between strains is used to assess their relationships. There is currently no universally accepted cutoff value for clustering strains that define an outbreak or linking the individuals involved. This study was conducted to estimate the threshold value of genomic variations among related strains within norovirus outbreaks. We carried out a literature search in the PubMed and Web of Science databases. SNP rates were defined as the number of SNPs/sequence length (bp) × 100%. The Mann-Whitney U-test was used in comparisons of the distribution of SNP rates for different sequence regions, genogroups (GI and GII), transmission routes, and sequencing methods. A total of 25 articles reporting on 108 norovirus outbreaks were included. In 99.1% of the outbreaks, the SNP rates were below 0.50%, and in 89.8%, the SNP rates were under 0.20%. Outbreak strains showed higher SNP rates when the P2 domain was used for sequence analysis (Z = -2.652, p = 0.008) and when an NGS method was used (Z = -3.686, p < 0.001). Outbreaks caused by different norovirus genotypes showed no significant difference in SNP rates. Compared with person-to-person outbreaks, SNP rates were lower in common-source outbreaks, but no significant difference was found when differences in sequencing methods were taken into consideraton. SNP rates under 0.20% and 0.50% could be considered as the rigorous and relaxed threshold, respectively, of strain similarity within a norovirus outbreak. More data are needed to evaluate differences within and between various norovirus outbreaks.

Mapping Biological Risks Related to Necropsy Activities: Old Concerns and Novel Issues for the Safety of Health Professionals

Nowadays only a few studies on biological and environmental risk among healthcare workers are available in literature. The present study aims to assess the health operator’s risk of contact with microorganisms during necropsy activities, to evaluate the efficiency of current protections, to identify possible new sources of contact, and to point out possible preventive measures. In addition, considering the current pandemic scenario, the risk of transmission of SARS-CoV-2 infection in the dissection room is assessed. The objectives were pursued through two distinct monitoring campaigns carried out in different periods through sampling performed both on the corpses and at the environmental level.

A Comprehensive Molecular Epidemiological Analysis of SARS-CoV-2 Infection in Cyprus from April 2020 to January 2021: Evidence of a Highly Polyphyletic and Evolving Epidemic

The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) resulted in an extraordinary global public health crisis. In early 2020, Cyprus, among other European countries, was affected by the SARS-CoV-2 epidemic and adopted lockdown measures in March 2020 to limit the initial outbreak on the island. In this study, we performed a comprehensive retrospective molecular epidemiological analysis (genetic, phylogenetic, phylodynamic and phylogeographic analyses) of SARS-CoV-2 isolates in Cyprus from April 2020 to January 2021, covering the first ten months of the SARS-CoV-2 infection epidemic on the island. The primary aim of this study was to assess the transmissibility of SARS-CoV-2 lineages in Cyprus. Whole SARS-CoV-2 genomic sequences were generated from 596 clinical samples (nasopharyngeal swabs) obtained from community-based diagnostic testing centers and hospitalized patients. The phylogenetic analyses revealed a total of 34 different lineages in Cyprus, with B.1.258, B.1.1.29, B.1.177, B.1.2, B.1 and B.1.1.7 (designated a Variant of Concern 202012/01, VOC) being the most prevalent lineages on the island during the study period. Phylodynamic analysis showed a highly dynamic epidemic of SARS-CoV-2 infection, with three consecutive surges characterized by specific lineages (B.1.1.29 from April to June 2020; B.1.258 from September 2020 to January 2021; and B.1.1.7 from December 2020 to January 2021). Genetic analysis of whole SARS-CoV-2 genomic sequences of the aforementioned lineages revealed the presence of mutations within the S protein (L18F, ΔH69/V70, S898F, ΔY144, S162G, A222V, N439K, N501Y, A570D, D614G, P681H, S982A and D1118H) that confer higher transmissibility and/or antibody escape (immune evasion) upon the virus. Phylogeographic analysis indicated that the majority of imports and exports were to and from the United Kingdom (UK), although many other regions/countries were identified (southeastern Asia, southern Europe, eastern Europe, Germany, Italy, Brazil, Chile, the USA, Denmark, the Czech Republic, Slovenia, Finland, Switzerland and Pakistan). Taken together, these findings demonstrate that the SARS-CoV-2 infection epidemic in Cyprus is being maintained by a continuous influx of lineages from many countries, resulting in the establishment of an ever-evolving and polyphyletic virus on the island.