Bayesian Estimation for the Coefficients of Variation of Birnbaum–Saunders Distributions

The Birnbaum–Saunders (BS) distribution, which is asymmetric with non-negative support, can be transformed to a normal distribution, which is symmetric. Therefore, the BS distribution is useful for describing data comprising values greater than zero. The coefficient of variation (CV), which is an important descriptive statistic for explaining variation within a dataset, has not previously been used for statistical inference on a BS distribution. The aim of this study is to present four methods for constructing confidence intervals for the CV, and the difference between the CVs of BS distributions. The proposed methods are based on the generalized confidence interval (GCI), a bootstrapped confidence interval (BCI), a Bayesian credible interval (BayCI), and the highest posterior density (HPD) interval. A Monte Carlo simulation study was conducted to evaluate their performances in terms of coverage probability and average length. The results indicate that the HPD interval was the best-performing method overall. PM 2.5 concentration data for Chiang Mai, Thailand, collected in March and April 2019, were used to illustrate the efficacies of the proposed methods, the results of which were in good agreement with the simulation study findings.

Norovirus GII.2[P16] strain in Shenzhen, China: a retrospective study

Background Norovirus (NoV) is the main cause of non-bacterial acute gastroenteritis (AGE) outbreaks worldwide. From September 2015 through August 2018, 203 NoV outbreaks involving 2500 cases were reported to the Shenzhen Center for Disease Control and Prevention. Methods Faecal specimens for 203 outbreaks were collected and epidemiological data were obtained through the AGE outbreak surveillance system in Shenzhen. Genotypes were determined by sequencing analysis. To gain a better understanding of the evolutionary characteristics of NoV in Shenzhen, molecular evolution and mutations were evaluated based on time-scale evolutionary phylogeny and amino acid mutations. Results A total of nine districts reported NoV outbreaks and the reported NoV outbreaks peaked from November to March. Among the 203 NoV outbreaks, 150 were sequenced successfully. Most of these outbreaks were associated with the NoV GII.2[P16] strain (45.3%, 92/203) and occurred in school settings (91.6%, 186/203). The evolutionary rates of the RdRp region and the VP1 sequence were 2.1 × 10–3 (95% HPD interval, 1.7 × 10–3–2.5 × 10–3) substitutions/site/year and 2.7 × 10–3 (95% HPD interval, 2.4 × 10–3–3.1 × 10–3) substitutions/site/year, respectively. The common ancestors of the GII.2[P16] strain from Shenzhen and GII.4 Sydney 2012[P16] diverged from 2011 to 2012. The common ancestors of the GII.2[P16] strain from Shenzhen and previous GII.2[P16] (2010–2012) diverged from 2003 to 2004. The results of amino acid mutations showed 6 amino acid substitutions (*77E, R750K, P845Q, H1310Y, K1546Q, T1549A) were found only in GII.4 Sydney 2012[P16] and the GII.2[P16] recombinant strain. Conclusions This study illustrates the molecular epidemiological patterns in Shenzhen, China, from September 2015 to August 2018 and provides evidence that the epidemic trend of GII.2[P16] recombinant strain had weakened and the non-structural proteins of the recombinant strain might have played a more significant role than VP1.

Integration Of Statistical Techniques For Improving Contact Tracing Efforts To Stop The Spread Of Covid-19 Cases In Nigeria

COVID-19 is battling with many countries in the world, including Nigeria, and it has affected various sectors. Contact tracing technique without Statisticians in the team as recommended by WHO is being used in Nigeria to curb the spread of COVID-19 virus, yet confirmed cases is on the increase daily. This study proposed the integration of Statistical techniques for improving contact tracing efforts to stop the spread of the virus. A fitted model using the R package, and Adaptive Cluster Sampling mechanism was embedded. Parameters of the model were estimated using Markov Chain Monte-Carlo (MCMC) Algorithm with Winbugs software. Trace plot and correlogram were used for MCMC diagnostics to examine the goodness of fit of the model. The fitted model was used to obtain a predictive distribution for predicting the estimated number of COVID-19 carriers in Nigeria. The model has a good fit since It converged to the representation of the target posterior within the 95% highest posterior density (HPD) interval, its chains mixed well, and autocorrelation is quite similar at each lag. Estimated number of COVID-19 carriers were well estimated and higher in each state than confirmed cases. The present contact tracing process is inefficient to track COVID-19 carriers, hence integrated contact tracing technique with the involvement of Statisticians was recommended. .

Phylodynamics of SARS-CoV-2 transmission in Spain

ObjectivesSARS-CoV-2 whole-genome analysis has identified three large clades spreading worldwide, designated G, V and S. This study aims to analyze the diffusion of SARS-CoV-2 in Spain/Europe.MethodsMaximum likelihood phylogenetic and Bayesian phylodynamic analyses have been performed to estimate the most probable temporal and geographic origin of different phylogenetic clusters and the diffusion pathways of SARS-CoV-2.ResultsPhylogenetic analyses of the first 28 SARS-CoV-2 whole genome sequences obtained from patients in Spain revealed that most of them are distributed in G and S clades (13 sequences in each) with the remaining two sequences branching in the V clade. Eleven of the Spanish viruses of the S clade and six of the G clade grouped in two different monophyletic clusters (S-Spain and G-Spain, respectively), with the S-Spain cluster also comprising 8 sequences from 6 other countries from Europe and the Americas. The most recent common ancestor (MRCA) of the SARS-CoV-2 pandemic was estimated in the city of Wuhan, China, around November 24, 2019, with a 95% highest posterior density (HPD) interval from October 30-December 17, 2019. The origin of S-Spain and G-Spain clusters were estimated in Spain around February 14 and 18, 2020, respectively, with a possible ancestry of S-Spain in Shanghai.ConclusionsMultiple SARS-CoV-2 introductions have been detected in Spain and at least two resulted in the emergence of locally transmitted clusters, with further dissemination of one of them to at least 6 other countries. These results highlight the extraordinary potential of SARS-CoV-2 for rapid and widespread geographic dissemination.

2453. Prolonged Local Epidemic of an XDR P. aeruginosa Subclade of High-Risk Clonal Complex 298

Background Antimicrobial resistance (AMR) poses an increasing challenge to the treatment of the nosocomial pathogen Pseudomonas aeruginosa, with the majority of highly resistant infections caused by relatively few high-risk clones. We investigated the role of clonal complex 298 (CC298: ST298 and ST446) in multidrug-resistant (MDR) and extensively drug-resistant (XDR) infections at Northwestern Memorial Hospital (NMH). Methods We determined the AMR of 40 whole-genome sequenced CC298 isolates, including 30 from patients at NMH in Chicago (2000–2017), 7 from hospital environments (e.g., sinks) in Chicago (2017–2018), and 3 from patients at Brigham and Women’s Hospital (BWH) in Boston (2015–2016). We used phylogenetics to assess the population structure of these isolates and 38 additional publicly available CC298 genomes. We interrogated the genomes of NMH CC298 isolates to uncover drivers of AMR. Results NMH CC298 isolates showed high rates of AMR, with 76.7% (23/30) MDR and 46.7% (14/30) XDR. Phylogenetic analysis revealed that 21/23 MDR (13/14 XDR) isolates from NMH formed a subclade of ST298, termed ST298*, as of yet not seen elsewhere. A time-scaled phylogeny of ST298* indicates a last common ancestor in 1980 (mean 1980.8, 95% HPD interval 1973.3–1987.4), with XDR ST298* isolates seen between 2001 and 2017. Many ST298* isolates, including all XDR isolates, harbored a large plasmid with an AMR class 1 integron. This plasmid is part of a family of large Pseudomonas genus plasmids. By comparing a plasmid-cured strain to its parent, we show that the plasmid imparts resistance to gentamicin and piperacillin–tazobactam. In the parental strain we detect T83I GyrA and S87L ParC substitutions known to cause fluoroquinolone resistance, showing that mutational resistance also contributes to the high AMR of ST298*. Publicly available genomes and previous reports indicate that CC298 has caused infections worldwide with multiple instances of significant AMR. Conclusion The repeated isolation of XDR ST298* P. aeruginosa at NMH over 16 years raises concern for the ability of this strain to persist in the healthcare environment. With this local epidemic and additional reports of MDR CC298 isolates around the world, we argue that CC298 should be considered a high-risk clone. Disclosures All authors: No reported disclosures.