Objective:To monitor the changes in specific IgM and IgG antibodies in patients diagnosed with COVID-19 after SARS-CoV-2 infection, and analyze their clinical significance.Methods:A total of 168 serum samples were collected from 56 COVID-19 patients with different disease courses who were positive for nucleic acid test at Henan Center for Disease Control and Prevention on January 8, 2020 and February 21, 2020. Serum samples from 25 healthy people excluded from COVID-19 were used as control group. IgM and IgG antibodies against SARS-CoV-2 were detected by chemiluminescence method.Results:IgM antibody increased sharply in 1-3 weeks after onset, and reached the peak value (21.78 AU/ml) in the 3rd week after onset. IgG antibody increased the most in 3-6 weeks after onset, and reached the peak value (81.58 AU/ml) in the 9th week after onset. The levels of IgM and IgG antibodies were closely correlated with age and disease course ( P<0.05). The antibody level of 30-60 years old group was the highest, the IgM antibody positive rate and antibody level of acute stage and previous infection were lower than that of recovery stage, and the IgG antibody positive rate and antibody level of acute stage were lower than that of recovery stage and previous infection. During the whole course of the disease, the levels of IgM and IgG antibodies increased gradually in the acute stage, reached the peak in the recovery stage, and decreased and maintained at a certain level in the past infection. Conclusions:Serum SARS-CoV-2 IgM and IgG antibody detection can be used as auxiliary diagnostic indicators for COVID-19, and its continuous observation is helpful for epidemiological investigation, serological diagnosis and disease course monitoring.

Objective:To analyze the evolutionary characteristics and variations of 2019 novel coronavirus (2019-nCoV) strains imported from abroad in Henan Province.Methods:A total of 16 imported cases of coronavirus disease 2019 (COVID-19) reported in Henan Province from May to December 2020 were enrolled. The throat swab specimens from the patients were collected and sent to the Henan Provincial Center for Disease Control and Prevention for whole genome sequencing. Taking SARS-CoV-2 Wuhan-Hu-1 published in Global Initiative on Sharing All Influenza Data (GISAID) as the reference sequence, the sequences were aligned and analyzed by MEGA X, and the phylogenetic tree was constructed by the maximum likelihood method.Results:Among 16 cases, 13 cases were imported from Russia, two cases were imported from Myanmar, and one case was imported from Ukraine. A total of 16 strains of 2019-nCoV genomes with the lengths of 29 804 bp to 29 882 bp were obtained. A total of 145 nucleotide mutations and 80 amino acid mutations were detected. Nucleotide variations of C241T, C3037T, C14408T, A23403G and the amino acid variation of D614G in spike protein were detected in all sequences. Meanwhile, insertion A at the site of 29704 was found in BetaCov/HEN02/Human/2020, BetaCov/HEN04/Human/2020 and BetaCov/HEN05/Human/2020. Deletion variation was not found. Phylogenetic analysis showed that there was no correlation between the 16 strains and currently epidemic variants of concern (VOC) .Conclusion:From May to December 2020, the detection of viral genome mutations in the imported cases of Henan Province shows randomness and diversity, while the strains are not VOC.

Objective:To analyze the specific immunoglobulin G (IgG) antibodies level in the population after the coronavirus disease 2019 (COVID-19) pandemic in Henan Province.Methods:A total of 5 178 peripheral venous blood samples were collected from 10 districts (counties) in Henan Province according to the national seroepidemiological survey program for COVID-19, and the method of cluster random sampling was adopted from March 6 to 15, 2023. Descriptive analysis was used for the basic data, history of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination, SARS-CoV-2 infection of the respondents. The specific IgG antibody of SARS-CoV-2 was detected using chemiluminescence method. Statistical analysis was performed by using rank sum test, Kruskal Wallis test, and Dunn′s test.Results:The overall positive rate of SARS-CoV-2-specific IgG antibody was 83.35%(4 316/5 178). There were statistically significant differences in the specific IgG antibodies against SARS-CoV-2 produced by people of different sexes, different ages, infected or not, vaccinated or not, and vaccinated with different doses of SARS-CoV-2 vaccine ( Z=3.60, H=195.32, Z=6.10, 18.08, H=382.70, respectively, all P<0.001). The specific IgG antibodies produced by unvaccinated+ uninfected group, unvaccinated+ infected group, vaccinated+ uninfected group, and vaccinated+ infected group were 3.54(0.98, 11.00), 60.65(2.33, 84.80), 133.00(59.80, 173.00), and 142.00(98.30, 176.00), respectively. And the difference was statistically significant( H=354.62, P<0.001). The specific IgG antibodies of uninfected people increased with the increase of inoculum times( H=287.00 and 98.48, both P<0.001). The specific IgG antibodies of people who were not infected with SARS-CoV-2 in the groups of whose interval from the last inoculation of SARS-CoV-2 vaccine to blood collection was less than three months, three to six months and more than six months were 171.86(156.04, 196.57), 71.71(17.08, 110.38) and 132.14(57.59, 172.25), respectively, and the difference was statistically significant ( H=19.93, P<0.001). Among them, the absolute difference between the less than three months group and the three to six months group was statistically significant ( Z=3.67, P<0.001), and the absolute difference between the less than three months group and the more than six months group was statistically significant ( Z=3.47, P<0.001). The specific IgG antibodies level in the less than three months group was the highest. Conclusions:There is a certain correlation between the number of SARS-CoV-2 vaccine doses and the specific IgG antibodies level in uninfected people. The specific IgG antibodies could maintain a high level for three months after immunization.

Objective:To analyze the dynamic changes and possible influencing factors of anti-2019 novel Coronavirus (2019-nCoV) neutralizing antibody in confirmed Coronavirus Disease 2019 (COVID-19) cases.Methods:Microneutralization was used to test the anti-2019-nCoV neutralizing antibody. Excel 2007 and SPSS 22.0 were used for data processing and analysis.Results:There were 420 serum samples collected from 155 confirmed COVID-19 cases. These serum samples contained acute phase serum, convalescent phase serum and serum from cases recovered for about six months. The sampling time was 0-221 days after the onset of COVID-19. The geometric mean titer (GMT) of anti-2019-nCoV neutralizing antibody was 1∶13 at 1 week, and 1∶31 at 2 week. The titers of anti-2019-nCoV neutralizing antibody of individual cases were still<1∶4 on the 15 th day. The GMT was all over 1: 52 (13×4) at 6-32 week. Taking 1: 64 as the cut-off point, the serum anti-2019-nCoV neutralizing antibody positive rates was 30.56% in acute phase serum samples (0-14 d, 0-2 w), 82.31% in convalescent phase serum samples (36-63 d, 6-9 w) and 86.52% in serum samples from cases recovered for about six months (183-210 d, 27-30 w). Statistical analysis showed that there was no significant difference in anti-2019-nCoV neutralizing antibody levels at the other weeks except 1-2 week ( χ2=9.270, P=0.931), there was no statistically differences in gender, age and occupation of the cases, and also between the normal and mild cases ( P>0.05). Conclusions:The serum anti-2019-nCoV neutralizing antibody level is only statistically correlated with the disease progression of COVID-19, and maintain the protective level from 3 to 30 week.

Objective:To analyze the genetic evolution and molecular characteristics of H7N9 avian influenza virus (AIV) isolated in a live poultry market.Methods:Samples such as poultry feces, sewage, and hair removal machine and chopping board swabs were collected. Real-time fluorescent quantitative PCR was used to detect influenza A virus and H7N9 AIV in the samples. The whole genome of H7N9 AIV was amplified with influenza A virus universal primers and sequenced. BLAST and MEGA X were used for sequence alignment, phylogenetic analysis and molecular characterization.Results:Seven poultry-related environment samples were collected in the live poultry market in Xuchang city in February 2023, and four were positive for H7N9 AIV. The whole genome sequences of three H7N9 AIV isolates were successfully obtained, and the isolates shared high nucleotide identity in different genes (98.37%-100.00%). BLAST analysis showed they were highly identical to H7N9 strains isolated from domestic poultry in China from 2020 to 2021. Genetic evolution analysis showed that the three isolates clustered in the same branch and were closer to the recent environmental isolates than to the recent strains isolated from human or avian. Through comparison with the sequences of the representative strains in different periods, it was found that the isolated strains in this study showed high avian pathogenicity with four amino acids KRAA inserted at the cleavage site; the hemagglutinin receptor-binding site was QSG, which was an avian binding receptor; there was a G186I mutation in hemagglutinin. Mammalian-adaptive mutation E627K was not detected in polymerase basic protein 2. Mutations (R292K and I38T) associated with drug resistance to neuraminidase inhibitor (oseltamivir) and polymerase acidic protein inhibitor (baloshavir) were not detected, suggesting that these isolates remained susceptible to these drugs. A S31N mutation was found in M2 protein, indicating they were resistant to alkamines.Conclusions:The three H7N9 AIV strains isolated in the live poultry market have high avian pathogenicity, but there are no significant increase in mutations related to the binding ability to human receptors, mammalian pathogenicity, viral transmissibility, or drug resistance as compared with previous representative strains causing human or avian infection.

Objective:To analyze the reinfection rates in people previously infected with SARS-CoV-2 in Zhengzhou and Yuzhou cities (first infected with Delta/B.1.617.2 variant), and Anyang city (first infected with Omicron/BA.1.1 variant) in January 2022 and the population characteristics, and compare the differences in antibody levels among different populations.Methods:Serum samples were collected from 371 previously infected, 134 reinfected and 19 uninfected people for IgG antibody detection. Among them, serum samples from 45 previously infected, 44 reinfected and 19 uninfected people were tested with different novel coronavirus variants (early original strain, BA.5.2 variant, XBB.1.5 variant) for neutralizing antibody detection.Results:The rate of reinfection was 32.82% (85/259) in Zhengzhou and Yuzhou cities, and 19.92% (49/246) in Anyang city. The IgG antibody level in reinfected people was higher than that in previously infected and uninfected people ( P<0.05). The IgG antibody level in uninfected group was higher in people vaccinated within three months than in those vaccinated six months ago ( P<0.05). The IgG antibody level in the group receiving four doses of vaccine was higher than that in the group receiving three doses of vaccine ( P<0.05). The results of true virus neutralization antibody detection showed that in the Zhengzhou and Yuzhou cases, the level of neutralization antibody against the early original strain was higher than those against the BA.5.2 variant and the XBB.1.5 variant ( P<0.05), and the level of neutralizing antibody against BA.5.2 variant was higher than that against XBB.1.5 variant ( P<0.05). In Anyang city cases, the level of neutralizing antibody against the early original strain was higher than those against BA.5.2 variant and XBB.1.5 variant ( P<0.05); in the reinfected population, the level of neutralizing antibody against the early original strain was higher than that against the XBB.1.5 variant ( P<0.05). In addition, the levels of all neutralizing antibodies in both previously infected and reinfected people were higher than those in uninfected people ( P<0.05). The level of neutralizing antibody in the infected population in Zhengzhou and Yuzhou cities was higher than that in the infected population in Anyang city and in uninfected population ( P<0.05). The levels of antibodies against BA.5.2 and anti-XBB.1.5 variants in infected people in Zhengzhou and Yuzhou cities were higher than those in uninfected people ( P<0.05). The level of neutralizing antibody against BA.5.2 variants in the previously infected population in Anyang city was higher than that in the uninfected population ( P<0.05), and the level of neutralizing antibody against XBB.1.5 variants in the infected population in Anyang city was higher than that in the uninfected population ( P<0.05). Conclusions:After infection with SARS-CoV-2, the neutralizing antibodies produced in the human body have a certain cross-protection effect on other variants, but the antibody level will gradually decrease over time. Protection from a previous early SARS-CoV-2 variants infection against the current main circulating Omicron variants (such as XBB variants) is low, and the immunity conferred by pervious infection or booster vaccination may not be able to provide sufficient protection against new variants.

Objective:To analyze the genome characteristics and variations in nucleotides and amino acids of SARS-CoV-2 causing an outbreak in Henan Province in November 2021 and perform the traceability analysis.Methods:In this study, throat swab specimens from cases in the acute phase were collected and tested for the nucleic acids of SARS-CoV-2 by real-time fluorescent RT-PCR. SARS-CoV-2 nucleic acid-positive samples were subjected to high-throughput genome sequencing and whole-genome alignment analysis.Results:The median Ct values of ORF1ab gene and N gene in 70 positive specimens was 26.41 (15.58 to 39.27) and 24.43 (12.04 to 39.74), respectively. Compared with the sequence of Wuhan-Hu(NC_045512) reference strain, 47 to 49 nucleotide mutations sharing 47 nucleotide mutation and 41 amino acid mutations were found in 63 strains of successfully sequenced SARS-CoV-2. Nine nucleotide mutations and 12 amino acid mutations were found in the spike protein. The index case shared 47 mutations with the Russian imported cases in Henan Province on October 14 and the local cases in Jiangxi Province in October. Moreover, their genomes were highly homologous and they all belonged to the Delta variant (AY.122 evolutionary branch).Conclusions:Continuous monitoring of imported COVID-19 cases and prolonging the period of quarantine were needed to reduce the risk of local outbreak and epidemic caused by imported COVID-19 cases. Analysis of the genomic characteristics of SARS-CoV-2 and the variations in nucleotides and amino acids was conducive to trace the origin of COVID-19 outbreak quickly and provide reference for precise control.