ObjectiveTo establish an adjusted Serfling regression model to estimate the excess cases and the excess epidemic period of hand-foot-mouth disease (HFMD) in Beijing from 2011 to 2019, so as to provide data support and decision-making basis for HFMD prevention and control. MethodsThe weekly number of HFMD cases in Beijing from 2011 to 2019 was utilized for adjusted the Serfling regression model. Then the adjusted model was used to fit the baseline and epidemic threshold of HFMD in Beijing from 2011 to 2019, calculating the excess cases and determining the excess epidemic period. ResultsA total of 279 306 cases of HFMD were reported in Beijing from 2011 to 2019, with the climax of the disease occurring in summer and autumn. After adjusting the fitting R² of the Serfling regression model to 0.773, a total of 10 excess epidemic periods totaling 92 weeks were estimated, mainly occurring in summer. The highest number of excess cases during an excess epidemic period was found in 2014 (1 272 cases, 95%CI: 990‒1 554), accounting for 65.04% of the actual cases (95%CI: 50.62%‒79.46%). ConclusionThe adjusted Serfling regression model fits well and can be utilized for early warning of HFMD and estimating the disease burden caused by HFMD.

Objective To investigate the epidemiological characteristics of local visceral leishmaniasis in Beijing Municipality from 2021 to 2023, so as to provide insights into formulation of the visceral leishmaniasis control strategy. Methods Epidemiological data of visceral leishmaniasis cases reported in Beijing Municipality from 2021 to 2023 were collected from the National Health Informatization Disease Prevention and Control Information System, and the epidemiological characteristics of local visceral leishmaniasis cases were analyzed using a descriptive epidemiological method. In November 2021 and 2023, 50 to 100 permanent residents were voluntarily selected within a 100 meter radius of sites where patients lived or acquired Leishmania infections, and venous blood was sampled for anti-Leishmania antibody testing. Venous blood was sampled from dogs for anti-Leishmania antibody testing in natural villages where patients lived or acquired Leishmania infections, or in districts where Leishmania infected dogs were reported. In addition, sandflies were captured with CO₂ mosquito traps and fine mesh nets in natural villages where patients lived or acquired Leishmania infections from May to September, 2021 and 2023, for sandfly species identification. Results A total of 4 local visceral leishmaniasis cases were reported in Beijing Municipality from 2021 to 2023, with ages of 2 to 77 years, and acquiring Leishmania infections in Mentougou District (2 cases), Changping District (1 case), and Yanqing District (1 case). The anti-Leishmania antibody testing was all negative in 73 human blood samples and the sero-prevalence of anti-Leishmania antibody was 25.00% in 36 venous blood samples from domestic dogs in 2021, with a total of 4 520 Phlebotomus chinensis captured. The sero-prevalence of anti-Leishmania antibody was 0.51% in 198 human blood samples and 13.58% in 243 venous blood samples from domestic dogs in 2023, with 16.10%, 25.00%, 17.78% and 3.13% sero-prevalence in dogs sampled from Mentougou District, Changping District, Yanqing District and Haidian District, respectively (P = 0.011), while a total of 1 712 Ph. chinensis were captured, including 1 421 female sandflies (86.54%). Conclusions The prevalence of local visceral leishmaniasis was low in Beijing Municipality from 2021 to 2023; however, there is a risk of further spread in the epidemic foci. Intensified visceral leishmaniasis surveillance and control is recommended.

Objective:To disclose phylogenetic and antigenic characteristics of hemagglutinin (HA) gene of influenza B virus (Victoria) (BV) in the 2023-2024 influenza surveillance season in Beijing, and understand the matching with influenza vaccine component strain.Methods:Pharyngeal swab specimens from influenza like-illness (ILI) in the 2023-2024 influenza surveillance season were collected from surveillance network labs in Beijing and BV strains were isolated through MDCK or chicken embryo culture. After extracting nucleic acid, HA gene was amplified and sequenced. The nucleotide and amino acid sequence identity were conducted and the maximum likelihood method in Mega 5.0 software was used to construct the phylogenetic tree of HA gene. N-glycosylation sites of HA were performed online. Furthermore, three-dimensional structure of HA was available from SWISS-MODEL homologous modeling. Hemagglutination inhibition (HI) tests were performed to analyze antigenic characteristics of HA of BV strains.Results:Fifty-four BV strains were randomly selected to be analyzed further. Compared with the HA gene of this influenza season vaccine strain (B/Austria/1359417/2021), there are three amino acid mutations among all BV strains, two of which are located in two different antigenic determinants. Furthermore, the phylogenetic tree analysis revealed that only one subgroup of 1A.3a.2 was circulating simultaneously. All BV strains are located in Clade 1A.3a.2 subgroup, and in the same subgroup with that of the vaccine component BV strain in 2023-2024. All BV strains have the same glycosylation sites as that of the vaccine component BV strain in 2023-2024. Antigenic analysis showed that all BV strains were antigenically similar with its vaccine strain.Conclusions:In the 2023-2024 influenza surveillance season, the prevalent BV strains in the population in Beijing city are located in Clade 1A. 3a. 2 subgroup. The antigen matching between BV epidemic strains and vaccine BV components is relatively high during this surveillance season.

Objective:To investigate the pathogen spectrum and the epidemiological characteristics of hospitalized severe acute respiratory tract infection (SARI) cases in a sentinel hospital in Tongzhou District of Beijing from 2019 to 2022, and provide reference for scientific prevention and control of SARI.Methods:This study enrolled SARI patients in the Beijing Luhe Hospital from January 2019 to December 2022. Nasopharyngeal swabs or respiratory secretions of the patients were collected and analyzed by quantitative real-time PCR to detect the pathogens and their types. The epidemiological and clinical characteristics of the cases were analyzed.Results:In this study, 1 124 SARI cases were enrolled, of which 379 were positive for respiratory pathogens with a detection rate of 33.72%. Most of the SARI cases were positive for bacteria pathogens, and the detection rates of Mycoplasma pneumoniae, Streptococcus pneumoniae, and Stenotrophomonas maltophilia were high. Influenza A virus, parainfluenza virus, and respiratory syncytial virus were the main viral pathogens detected in the cases. There were significant differences in the number of cases and the detection rate of respiratory pathogens among different age groups (χ 2=555, P=0.000 1). The predominant pathogens in different years were different. Mycoplasma pneumoniae [27.27% (51/187)] and influenza A virus [17.65% (33/187), ] were the predominant pathogens in 2019; parainfluenza virus [16.67% (10/60)], Mycoplasma pneumoniae [11.67% (7/60)], and Haemophilus influenzae [11.67% (7/60)] were the predominant pathogens in 2020; Stenotrophomonas maltophilia [24.39% (20/82)] and respiratory syncytial virus [19.51% (16/82)] were the predominant pathogens in 2021; Stenotrophomonas maltophilia [20% (10/50)] and parainfluenza virus [12% (6/50)] were the predominant pathogens in 2022. Conclusions:Most of the SARI cases in Tongzhou district of Beijing from 2019 to 2022 are caused by bacteria. More attention should be paid to the prevalence of Stenotrophomonas maltophilia and Mycoplasma pneumoniae, as well as the prevalence of respiratory syncytial virus, parainfluenza virus, and influenza A virus. The predominant pathogens change every year from 2019 to 2022. Therefore, the prevention and control strategies should be made accordingly. This study provides basis data for the national respiratory multipathogen surveillance program.

Objective:To investigate the phylogenetic and antigenic characteristics of hemagglutinin (HA) gene of influenza B/Victoria lineage (BV) viruses in Beijing during the 2021-2022 influenza surveillance season, and to analyze whether the circulating BV viruses match the vaccine strain.Methods:Pharyngeal swab specimens from influenza like-illness (ILI) cases in the 2021-2022 influenza surveillance season were collected from surveillance network labs in Beijing and cultured in MDCK cells and chicken embryo to isolate BV viruses. Nucleic acids of the viruses were extracted, and the HA gene was amplified and sequenced. The nucleotide and amino acid sequence identity of the HA gene was analyzed using MEGA5.0 software. A phylogenetic tree of HA gene was constructed using the maximum likelihood method. The N-glycosylation sites in HA were predicted online. Three-dimensional structure of HA was constructed using SWISS-MODEL homologous modeling. Hemagglutination inhibition (HI) test was performed to analyze the antigenicity of BV viruses.Results:A total of 402 BV viruses were collected and 58 strains with full-length HA gene sequences were chosen for further analysis. Compared with the HA gene of this year′s vaccine strain (B/Washington/02/2019), there were 27 amino acid mutations, 11 of which were located in four different antigenic determinants. The phylogenetic analysis revealed that three subgroups of 1A.3, 1A.3a1, and 1A.3a2 co-circulated in Beijing with 54 strains (54/58, 93.10%) clustered to the Clade 1A.3a2, two strains (2/58, 3.45%) clustered to the Clade 1A.3a1, and two strains (2/58, 3.45%) in the same subgroup (Clade 1A.3) as the vaccine component BV strain in 2021-2022. Compared with the vaccine strain (B/Washington/02/2019), two BV strains had an additional N-glycosylation site at residue 197, while the other 56 strains showed no change in N-glycosylation sites. Antigenic analysis showed that 35 BV strains (35/58, 60.34%) were antigenically similar to the vaccine strain and 23 strains (23/58, 39.66%) were low-response strains.Conclusions:Three subgroups of BV viruses co-circulated in Beijing during the 2021-2022 influenza surveillance season. The predominant subgroup was Clade 1A.3a2 (93.10%), showing a certain genetic distance with the vaccine strain (B/Washington/02/2019). Nearly 40% (39.66%) of the viruses were low-response strains. This study indicated that continuous monitoring of the variations of influenza epidemic strains and timely providing laboratory basis for screening vaccine component strains were the basic technical guarantee for coping with influenza pandemic.

Objective:To understand the epidemic situation of Redondoviridae in Beijing and analyze its epidemiologic characteristics.Methods:Pharyngeal swab samples of healthy people and patients with acute respiratory infection in Beijing, including influenza like cases and severe acute respiratory infection (SARI) cases in hospitals were collected. Real time PCR was used to detect the nucleic acid of Redondoviridae. The positive samples were amplified and sequenced to analyze their species. The age and sex distribution of patients and species distribution of Redondoviridae were obtained through statistical analysis. Multiplex PCR was used to detect other common respiratory pathogens in the positive samples of Redondoviridae in influenza like cases and SARI cases, and the pathogenicity of Redondoviridae was analyzed.Results:The positive rates of Redondoviridae in healthy people and acute respiratory infection cases were 20.48% (189/923) and 11.23% (43/390), respectively, with a statistically significant difference ( P<0.05). The positive rate of male was higher than that of female in the healthy population, and the positive rate of the elderly group was higher than that of the adult group and the underage group, with a statistically significant difference ( P<0.05). The positive rate of male patients with acute respiratory tract infection was higher than that of female patients, but there was no significant difference. The proportion of Vientovirus in the positive samples of Redondoviridae was higher than that of Brisavirus, and the difference was statistically significant ( P<0.05). Among the throat swabs of respiratory tract infection cases, 43 were positive for Redondoviridae, of whom 24 were not detected for other pathogens. Conclusions:Redondoviridae widely exists in healthy people of all age groups in Beijing, and is also found in acute respiratory infection cases. The positive rate of Redondoviridae is different in different ages and genders. Both Vientovirus and Brisavirus were detected, and the proportion of Vientovirus was significantly higher than Brisavirus.

Objective:To analyze the genomic characteristics and variations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) derived from an outbreak in inbound flight in Aug, 2022 in Beijing, and provide reference data for disease prevention and control and risk assessment.Methods:Fifty respiratory tract specimens from all cases in this outbreak were collected. The digital PCR (ddPCR) was used to determine the viral loads of the specimens. The full genome of the viruses were sequenced by Next-generation sequencing. Then analuses were performed on the genetic identity, variations and phylogenesis.Results:The median of viral loads in all 50 samples were 5.57×10 4 copies/ml and 5.85×10 4 copies/ml, for ORF1ab gene and N gene, respectively. A total of 46 SARS-CoV-2 genomes were obtained, which all belonged to Omicron/BA.5. Two genome clusters were observed, involving 21 and 7 cases, with a nucleotide sequence identities of 99.993% and 99.997%, respectively. Conclusions:The studied outbreak was composed of two main clusters and other individual cases with Omicron/BA.5 virus overseas.

Objective:To characterize the epidemic of influenza in Beijing from 2022 to 2023 and the variation of gene and antigenicity of hemagglutinin (HA) of influenza A H3N2 virus, so as to provide scientific basis for influenza prevention and control in Beijing.Methods:Statistical analysis was carried out on the result of influenza pathogenic monitoring in Beijing from week 14, 2022 to week 20, 2023, and 79 strains of influenza A H3N2 virus were selected at different time and population sources, and their genetic variation and evolution characteristics were analyzed through HA gene amplification sequencing and antigenicity analysis.Results:From week 14, 2022 to week 20, 2023, 24 244 throat swabs of influenza like cases were collected in Beijing, and 4 987 influenza virus nucleic acid positive cases were detected, including 2 749 influenza A H3N2 positive cases, with a detection rate of 11.34%. Among the 79 strains, 50 strains (63.29%) showed low response, 94.44% of the strains from August to November 2022 had low response, and 54.10% of the strains from February to March 2023 had low response, with a statistically significant difference ( χ2=8.079, P=0.004). Compared with the vaccine strain A/Darwin/9/2021, the HA gene sequence of 79 strains of influenza A H3N2 showed nucleotide similarity of 97.47% to 98.47% and amino acid similarity of 97.05% to 98.17%. Genetic evolution analysis showed that the 18 strains isolated from August to November 2022 were all distributed in the 3C.2a1b.2a.1a.1 branch, while the 61 strains isolated from February to March 2023 all belonged to the 3C.2a1b.2a.3a.1 branch. Compared with the vaccine strain, there were multiple site mutations distributed at multiple antigenic determinants and receptor binding sites in A, B, C, D, and E. All strains had potential glycosylation sites of 8NST, 22NGT, 38NAT, 45NSS, 63NCT, 126NWT, 133NGT, 246NST, 285NGS, 483NET, while one strain missed 165NVT glycosylation sites; 55 strains between February and March 2023 missed 122NES glycosylation sites. Conclusions:The HA gene locus of influenza A H3N2 virus detected in Beijing from week 14, 2022 to week 20, 2023 showed multiple mutations, continuous monitoring of this subtype variation is crucial.

Objective:To understand the gene characteristics of Sapovirus from diarrhea cases in diarrhoeal disease clinics in Beijing.Methods:In 2019, stool samples were collected from diarrhea cases in diarrhoeal disease clinics in Beijing. The samples were used for the detection of nucleic acid of Sapovirus with real-time RT-PCR. Different RT-PCR methods were used for the partial gene segment amplification in the capsid protein VP1 region and the polymerase RdRp region, and sequencing was conducted for amplified positive products. The sequences were aligned with software BioEdit 7.0.9.0 and analyzed with software Mega 6.06.Results:The overall detection rate of Sapovirus was 2.89% (44/1 522), the detection rate in children under 5 years old was 3.34% (18/539) and 2.64% (26/983) in children aged ≥5 years. The capsid protein VP1 region was sequenced in 23 strains belonging to 8 genotypes (GⅠ.2 had 6 strains, GⅠ.1 and GⅡ.3 had 5 strains, respectively, GⅠ.3 and GⅡ.5 had 2 strains, respectively, GⅠ.5, GⅡ.1 and GⅣ.1 had 1 strain, respectively). A total of 16 strains were detected in the cases aged ≥5 years, and the proportion of GⅠ.2 was highest (37.50%, 6/16), and 7 strains were detected in the cases under 5 years old, the proportions of GⅠ.1 and GⅡ.3 were highest (both 42.86%, 3/7); The internal similarity of each genotype was 95.5%-100.0%, and the similarity with the 51 reference strains of human or sewage sources in different years and different countries was 92.2%-100.0%. The polymerase RdRp region was sequenced in 25 strains belonging to 8 genotypes (GⅡ.P3 had 9 strains, GⅠ.P3 had 4 strains, GⅠ.P1, GⅠ.P2 and GⅡ.P1 had 3 strains, respectively, GⅠ.P5, GⅡ.P5 and GⅣ.P1 had 1 strain, respectively). Fifteen strains were detected in the cases aged ≥5 years, and GⅡ.P3 had the highest proportion (40.00%, 6/15). Ten strains were detected in the cases under 5 years old, and the proportions of GⅠ. P1, GⅡ.P1 and GⅡ.P3 were highest (all 30.00%, 3/10); The internal similarity of each genotype was 94.0%-100.0%, and the similarity with the 39 reference strains of human or sewage sources in different years and different countries was 90.2%-99.1%.Conclusions:Sapovirus is one of the pathogens among diarrhea cases in Beijing. The main genome is GⅠ and GⅡ, and the genotypes are diverse and dispersed. The main genotypes of diarrhea cases in people aged ≥5 years and less than 5 years are different.

Objective:To clarify the M protein ( emm gene) types and drug susceptibility characteristic variations of Group A Streptococcus (GAS) in children in Beijing. Methods:The GAS strains isolated from throat swab samples of children diagnosed with scarlet fever and pharyngeal infection in scarlet fever etiology surveillance sentinel hospitals in 16 districts of Beijing in 2018, 2019 and 2021 were analyzed retrospectively.PCR amplification and sequencing were used for emm genotyping, and the minimum inhibitory concentrations (MIC) of 10 antibiotics were determined by the broth microdilution method.The data were analyzed using χ2 test and Fisher′ s exact method between groups. Results:A total of 557 GAS strains were collected, and 11 emm genotypes ( emm1, emm3, emm4, emm6, emm11, emm12, emm22, emm75, emm89, emm128, and emm212) were detected.Of 557 strains, 238 trains were of emm1 type (42.73%), 271 strains were of emm12 type (48.65%) and 48 strains were of other emm types (8.62%). The detection rates of emm1, emm12 and other emm type genes in 2018, 2019, and 2021 were [37.50% (105/280 strains), 57.14% (160/280 strains), 5.36% (15/280 strains)], [49.05% (129/263 strains), 39.54% (104/263 strains), 11.41% (30/263 strains)], and [28.57% (4/14 strains), 50.00% (7/14 strains), 21.43% (3/14 strains)], respectively.In children infected with emm12 in 2018 and 2019, there were more children under 6 years old than children over 6 years old (62.50% vs.46.88%, 46.36% vs.30.36%) (χ 2=7.182, 6.973; all P<0.05). Drug susceptibility testing results suggested that 225 randomly selected GAS strains were all 100.00% sensitive to 7 antibiotics including Penicillin, Levofloxacin, Meropenem, Linezolid, Cefotaxime, Cefepime and Vancomycin.The rates of resistance to Erythromycin, Tetracycline and Clindamycin were [88.57% (93/105 strains), 87.62% (92/105 strains), 86.67% (91/105 strains)], and [94.34% (100/106 strains), 94.34% (100/106 strains), 87.74% (93/106 strains)] in 2018 and 2019, respectively.The test strains were 100.00% (14/14 strains) resistant to the above 3 antibiotics in 2021.MIC 50 and MIC 90 values of Penicillin in 2018, 2019, and 2021 were (0.03 mg/L, 0.03 mg/L), (0.03 mg/L, 0.06 mg/L), and (0.06 mg/L, 0.06 mg/L), respectively.Among 225 GAS strains, 207 strains had drug resistance and were resistant to more than one drug.Specifically, 94.69% (196/207 strains) were resistant to Erythromycin, Tetracycline and Clindamycin.About 4.35% (9/207 strains) were resistant to both Erythromycin and Clindamycin.A total of 0.97% (2/207 strains) were resistant to Erythromycin and Tetracycline. Conclusions:The emm genotypes of GAS in children in Beijing are diverse in 2018, 2019 and 2021.The dominant genotypes are emm12 and emm1, and emm12 is the main epidemiological type.GAS strains maintain highly resistant to Erythromycin, Clindamycin and Tetracycline, and sensitive to Penicillin and other antibiotics.However, MIC 50 and MIC 90 of Penicillin shows an ascending trend.