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.

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.

Global burden of disease attributable to high systolic blood pressure in older adults, 1990-2019: an analysis for the Global Burden of Disease Study 2019.

AIMS: High systolic blood pressure (HSBP), a significant public health challenge, has not been systematically studied in the elderly population in the context of global aging. Understanding the temporal trends of the disease burden associated with HSBP in the elderly population is essential to control and mitigate the harm caused by HSBP. METHODS AND RESULTS: We used the estimated data derived from the Global Burden of Disease Study to analyse the disease burden of HSBP among the elderly population by region, sex, and temporal changes from 1990 to 2019. We found that the number of deaths due to HSBP increased to 7.86 (95% UI: 6.89-8.82) million, with an increase of 54.1%, and the number of disability-adjusted life years (DALYs) increased to 146 (95% UI: 130-162) million, with an increase of 52.4%. Conversely, the death and DALY rates of HSBP decreased by -27.0 and -27.8%, respectively. At the national and regional levels, Australasia and other high socio-demographic index regions have made significant improvements in the burden of HSBP, while it remains high in other regions of the world. Additionally, the burden of HSBP in older men is greater than that in older women. CONCLUSION: Our findings indicate that the current prevention and control of HSBP in older adults is poor, with the total burden increasing significantly. There is an urgent need to implement feasible measures to resist HSBP and lessen the disparity of the global HSBP burden for older adults.