ABSTRACT
Domestic and foreign literatures related to the persistence of SARS-CoV-2 and the re-positive cases infected with SARS-CoV-2 were reviewed, and the characteristics and infectivity of the re-positive cases were analyzed to provide scientific evidence for the improvement of case management and the development of measures to stop the spread of SARS-CoV-2. Existing studies have shown that re-positive rate of SARS-CoV-2 ranged from 2.4% to 19.8%, the median of interval between re-positive detection and discharge was 4-15 days. Following the second course of the disease, the anti-SARS-CoV-2 IgM, IgG and IgA positive rates of the cases were 11.11%-86.08%, 52.00%-100.00% and 61.54%-100.00% respectively, the total antibody and neutralizing antibody positive rates were 98.72% and 88.46%. The viral load of the re-positive cases was lower than that in the initial infection. At least 3 380 re-positive cases have been reported globally. SARS-CoV-2 strains were isolated from the samples of 3 re-positive cases (1 immunodeficiency case and 2 cases with abnormal pulmonary imaging). There were close contacts that were infected by an asymptomatic case taking immunosuppressive agents. In conclusion, the infectivity of re-positive cases infected with SARS-CoV-2 is generally very low. Rare re-positive cases infected with SARS-CoV-2 might cause further transmission. The management approach for the re-positive cases can be based on the assessment of the individual transmission risk according to the pathogen detection results.
Subject(s)
Humans , Antibodies, Neutralizing , Antibodies, Viral , COVID-19 , Immunoglobulin M , SARS-CoV-2ABSTRACT
Objective@#To study the application of measles specific IgM and IgG antibody detection in classification of primary vaccination failure (PVF) and secondary vaccination failure (SVF).@*Methods@#Measles surveillance information system was used to collect measles confirmed cases in Tianjin, 2013-2015, and their blood specimens were collected, totally 284 cases were enrolled. Measles IgM and IgG were detected with enzyme-linked immunosorbent assay (ELISA), and the relative avidity index (RAI) was used to express the result of measles avidity. Measles IgM, IgG and IgM/IgG was analyzed with receiver operating characteristic (ROC) curve, the area under the ROC curve (AUC) as evaluation indicators. In addition, compared with a measles outbreak (26 cases) of a middle school in Tianjin in 2016, for making further verification on the diagnostic value of vaccination failure with IgM, IgG and IgM/IgG.@*Results@#The age of cases ranged was 0-58 years old, the interval median (P25, P75) of serum collection after rash onset was 2 (1, 4) days. The positive rate of measles IgM and IgG in acute phase specimens were 76.06% (216 cases) and 88.38% (251 cases). According to the ROC curve analysis, the area under the ROC curve (AUC) of IgM, IgG and IgM/IgG were 0.753, 0.891 and 0.952, indicating that IgM/IgG was the best index to distinguish PVF and SVF. The best cut off value for IgM/IgG was 0.06, the sensibility and specificity were 88.75% and 86.63%. When IgM/IgG >1, 96.30% cases were low-avidity (RAI <40%), only 1 case was equivocal response (RAI: 40%-60%). 97.14% cases were high-avidity (RAI >60%) when IgM/IgG <0.01, only 3 cases were equivocal response (RAI 40%-60%). The threshold of IgM/IgG was used to verify the measles outbreak of a middle school in Tianjin, 2016. In the acute phase specimens, 100% (26 cases) of IgM/IgG were <0.06, 84.62% (22 cases) of IgM/IgG were <0.01.@*Conclusion@#The detection of measles IgM and IgG with ELISA, and IgM/IgG is a valuable diagnostic tool to distinguish PVF and SVF.
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Objective@#The genetic characteristics of the human adenovirus type 53 (HAdV-53) strains isolated from Taiyuan city of Shanxi Province were studied to obtain the baseline data of their molecular characteristics.@*Methods@#Conjunctival swabs (n=79) were collected from epidemic keratoconjunctivitis (EKC) patients in Shanxi eye Hospital in 2016, and five HAdV-53 strains were obtained after virus isolation and identification based on the three major capsid genes sequences including Penton base, Hexon and Fiber gene. And the corresponding sequences of global epidemic HAdV-53 strains and the strains with the same genetic origin as HAdV-53 were also downloaded from GenBank database, and then the three gene database were established, respectively. With the database, phylogenetic tree was constructed, and the genetic and molecular evolutionary characteristics were analyzed with bioinformatics software.@*Results@#Five HAdV-53 strains in Shanxi Province in 2016 showed high consistency with the HAdV-53 strains prevalent in other countries in 1996-2014 (>99.8%). All HAdV-53 strains were in the same evolutionary branch with their recombinant source genotypes (HAdV-37 and HAdV-8) in Penton base and Fiber gene, respectively, and maintained a high degree of consistency in gene sequences. In Hexon gene, HAdV-53 strains were more closed to its recombinant source genotype HAdV-22, the nucleotide and amino acid sequences between two types were highly homologous, while HAdV-53 and HAdV-22 belonged to different evolutionary branches, and the evolution rate of HAdV-53 based on Hexon gene was 3.51×10-5 substitution/site/year.@*Conclusion@#HAdV-53 has become an important new ocular infectious pathogen of Taiyuan. HAdV-53 strain are relatively conservative and stable based on Penton base, Hexon, and Fiber gene.
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Objective@#To better understand the evolution and epidemiology of human adenovirus-55 (HAdV-55) and provide a scientific basis for the prevention and control of the epidemic of HAdV-55 in China.@*Methods@#HAdV-55 isolates from 5 provinces in China included Beijing, Hebei, Shandong, Hunan and Yunnan were collected during 2011-2014. The hexon, fiber and penton base gene were sequenced, and compared with other strains of HAdV-55 sequences downloaded from GenBank for homology and evolution analysis.@*Results@#During the past decade, HAdV-55 was found in 15 provinces throughout China. Genetic and phylogenetic analysis showed that the HAdV-55 virus is highly conservative in evolution due to aggregation in a branch in the evolutionary tree. However, bayesian phylogenetic tree shows a certain time evolution trend. The evolution rate of hexon and fiber gene of HAdV-55 are 5.228×10-5 and 1.238×10-4 substitutions/site/year respectively, and the latest coevolutionary ancestor tMRCA of hexon gene can be traced back to 1963.@*Conclusions@#HAdV-55 has been widely spread and continued circulating in China. Establishing effective monitoring system and conducting vaccine related research is very important for its control and prevention.
ABSTRACT
We wished to understand the genetic characteristics of enteric cytopathic human orphan (ECHO) virus type 6 (ECHO6) circulating in China. First, the partial VP1 coding region of six strains of the ECH-O6 virus isolated from cases of hand, foot and mouth diseases during routine surveillance in Hunan Province (China) from 2009 to 2014 were sequenced. Those sequences were analyzed along with 138 sequences of ECHO viruses covering five provinces of China and countries outside China retrieved from the GenBank database. A phylogenetic tree based on partial VPI was constructed, and it indicated that Chinese strains of the ECHO virus could form two distinct evolutionary branches: branch 1 and branch 2. All isolates of the ECHO virus from Hunan Province belonged to the 2c subranch, which revealed that they may share a common evolutionary origin. ECHO strains in branch 2 may be the predominant strains in China due to their wide geographic distribution and long period of circulation. We used nucleotide differences of >30%o as the basis of cluster division. ECHO, viruses could be divided into four clusters (A-D). Cluster D could be divided further into ten subclusters on the basis of nucleotide differences of 15%-30%. All ECHO6 isolates from Hunan Province belonged to the D7 subcluster. These data showed that the ECHO6 strains that circulated in Hunan Province in 2009-2014 were closely related to each other, and probably shared a common evolutionary origin. In addition, at least four distinct lineages of ECHO viruses have circulated in China.