A foodborne acute gastroenteritis outbreak caused by GII.P16-GII.2 norovirus in a boarding high school, Beijing, China: a case-control study.

OBJECTIVE: In December 2017, an acute gastroenteritis outbreak involving 61 students occurred in a boarding high school in Beijing, China. We conducted an outbreak investigation immediately in order to determine the cause of this outbreak and provide effective control measures. RESULTS: The laboratory inspection showed that this outbreak was caused by GII.P16-GII.2 norovirus. Risk factor analysis indicated that the lunch provided by Cafeteria 1 on Dec 12 might be the risk factor of the outbreak with an odds ratio (OR) of 3.800 (95% confidence interval [CI] 1.089-13.258). Additionally, a tray line server of Cafeteria 1 was found to have gastro-enteral symptoms recently. Based on the clinical symptoms and epidemiology investigation, the symptomatic server was considered to be the possible source of infection.

[Etiological detection of severe hand-food-mouth disease and related genetic characteristics of enterovirus type 71 infection in Beijing, 2010].

OBJECTIVE: To study the etiological detection on samples from severe hand-foot-mouth disease (HFMD) cases and the genetic characteristics of enterovirus type 71 (EV71) isolates from severe patients in Beijing, 2010. METHODS: Real-time RT-PCR was used to detect EV71 and Coxsackievirus A16 (CoxA16) and RD cells were used to separate virus strains from samples. Homogeneity of EV71 isolated strains were also analyzed. RESULTS: Four hundred and fourty-two severe cases were detected and 253 were positive, taking up 57.24% of the total (253/442). The overall positive detection rate on EV71 was 54.55% (138/253), with CoxA16 as 5.93% (15/253), and with other enterovirus group was 39.53% (100/253). The nucleotide homogeneity of VP1 within these 12 strains was 97.2% - 100.0%, and with Beijing strains in 2007 - 2010, Shandong strains in 2007 and Anhui Fuyang strains in 2008 and the Guangdong strains in 2008 as 94.0% - 99.9%. CONCLUSION: Severe HFMD cases were most oftenly caused by EV71 but less caused by CoxA16 or other enterovirus. The HFMD in 2010 in Beijing was mainly caused by EV71 subgenotype C4a with 4 transmission chains. Twelve isolated EV71 strains had high homogeneity with strains isolated from severe cases in Anhui Fuyang in 2007.

[Etiological surveillance and analysis of infectious diarrhea in Beijing in year 2010].

OBJECTIVE: To explore the pathogenic form, epidemic features and serotype distribution of the pathogenic bacteria causing infectious diarrhea in Beijing. METHODS: A total of 2118 samples of rectal swabs and stool specimens of diarrheal patients were collected from 6 surveillant intestinal tract clinics during the period between April and October, 2010. Enteric multiple pathogens including Vibrio cholerae, Vibrio parahaemolyticus, Salmonella, Shigella and diarrheagenic Escherichia coli were detected by the isolation culture, biochemical identification and serotyping methods. The population distribution, temporal distribution and serotype distribution of the above pathogenic bacteria were analyzed by descriptive statistical methods. RESULTS: 478 strains isolated from the total 2118 specimens were positive for pathogen detection, accounting to 22.6%. Among the 478 strains of pathogenic bacteria, Shigella accounting for 40.8% (195/478) was the most frequent pathogen, followed by Vibrio parahaemolyticus accouting for 23.8% (114/478), Salmonella accounting for 19.0% (91/478) and diarrheagenic Escherichia coli accounting for 4.8% (23/478). Enteric pathogenic bacteria spread mainly among adults aging between 20 and 39; and the distribution was different among different age groups, while the highest detected rate was in 30 - 39 age group, accounting for 27.2% (92/338). The detected rate of pathogenic bacteria showed evident seasonal variations, with a peak from July to October, whose detected rates were 23.5% (114/486), 32.8% (176/536), 36.1% (90/249) and 25.9% (29/112) respectively. The detected rates in other months were all under 16.0%. Shigella Sonnei was the dominant serotype, accounting for 83.1% (162/195). O3:K6 was the dominant serotype among Vibrio parahaemolyticus, accounting for 63.2% (72/114). Salmonella Enteritidis and Salmonella Typhimurium were dominant serotypes among Salmonella, accounting for 13.2% (12/91) and 12.1% (11/91) separately. Enterpathogenic Escherichia coli and enterotoxigenic Escherichia coli were the dominant serotypes among Diarrheagenic Escherichia coli, accounting for 69.6% (16/23) and 30.4% (7/23) respectively. CONCLUSION: The three main pathogenic bacteria causing infectious diarrhea in Beijing are Shigella, Vibrio parahaemolyticus, Salmonella; and there are obvious changes in the serotype distribution of Shigella and Samonella compared to previous years.

[Comparisons of epidemiological and clinical characteristics in children with hand-foot-mouth disease caused by Enterovirus 71 and Coxackievirus A16].

OBJECTIVE: To compare the differences of epidemiological and clinical characteristics in children with hand-foot-mouth disease (HFMD) caused by Coxsackievirus A16 (CA16) and Enterovirus 71 (EV71). METHODS: The samples of vesicle fluid and throat swabs of 108 children with HFMD were collected and detected for enterovirus by RT-PCR. The clinical data of children with EV71 and CA16 infection were retrospectively reviewed and compared. RESULTS: The total positive rate of enterovirus was 97.2% (105/108). Of the 105 cases, 56 cases were positive for EV71 (51.9%), 39 cases were positive for CA16 (36.1%), 2 cases were positive for other enterovirus (1.9%), and 8 cases were co-infected by EV71 and CA16 (7.4%). There were no significant differences in age and sex between EV71 and CV16 infected cases. The univariate analysis showed that the incidences of herpes of mouth, erythra of knees, and nose running in children infected by CA16 were higher than in those infected by EV71. The multivariate logistic regression analysis showed that the HFMD children who had erythra of knees had higher probability of CA16 infection. CONCLUSIONS: EV71 should be considered as the pathogen in children with HFMD who have no herpes of mouth, erythra of knees, and nose running.

[Epidemiological characteristics of infection for close contacts of pandemic (H1N1) 2009 in Beijing].

OBJECTIVE: To examine the epidemiological characteristics of infection for close contacts of pandemic (H1N1) 2009 and to provide scientific evidence for preparedness and response for the next pandemic. METHODS: A total of 613 index cases with clear information of close contacts and their 7099 close contacts, determined between May 16 and September 15, 2009, were included in this study. Based on data of epidemiological investigation, sampling and test of index cases and close contacts, the characteristics of infection for close contacts were described. RESULTS: 56.8% (348/613) of the index cases were male, and 43.2% (265/613) were female, and the median age was 20 years (range: 1 - 75 years). 49.6% (3518/7099) of the close contacts were male, and 49.5% (3514/7099) were female, but the sex information of 0.9% (67/7099) could not be recorded. The median age of the close contacts was 27 years (range: 0 - 99 years). 2.4% (167/7099) of close contacts were infected. The attack rates decreased with increasing age of close contacts (χ()2 = 27.87, P < 0.001), and were significantly different between various contact patterns of close contacts (χ()2 = 109.76, P < 0.001). 14.4% of the infected close contacts were asymptomatic. For close contacts with symptomatic infection, virus could be shed 4.5 days before illness onset, and the median generation time was 2.4 days. CONCLUSION: The attack rate of close contacts was very low; and the attack rates were different between various ages and contact patterns of close contacts. In this series 14% of cases with pandemic (H1N1) 2009 were asymptomatic. The symptomatic cases might have infectivity 1 day earlier before illness onset.

[Analysis on the etiological and molecular epidemiological characteristics of Vibrio parahaemolyticus in Beijing].

OBJECTIVE: To understand the etiological and molecular-epidemiological characteristics of Vibrio parahaemolyticus in Beijing. METHODS: Stool specimens from sporadic diarrheal patients were collected during April to December, 2010. Culture and serotyping were used to detect the Vibrio parahaemolyticus from the 2118 specimens. All the positive strains were tested for drug sensitivity by Kirby-Bauer method. Real-time PCR was used to detect the existence of three virulence genes tlh, tdh and trh. Molecular typing on Vibrio parahaemolyticus isolates was completed by pulsed field gel electrophoresis (PFGE). RESULTS: 114 out of the 2118 specimens were Vibrio parahaemolyticus positive, with the positive rate as 5.38%. 114 isolates belonged to 23 serotypes, with the dominant (63.16%) serotype as O3:K6. Strains isolated from clinical manifestation patients were resistant to antibiotics-ampicillin and gentamicin, while with high sensitivity to amoxicillin, ceftriaxone, chloromycetin, imipenem, nalidixic acid and tetracycline. Virulence gene detection was positive to tlh for all the strains, but most to tdh, while only one strain to trh. The positive rate of tdh among O3:K6 strains (98.61%) was higher than that in those non-O3:K6 strains (85.71%) (P = 0.0098). 114 isolates were discriminated into 54 different PFGE patterns, while 72 O3:K6 strains into 34 patterns without the clustering characteristic. CONCLUSION: Vibrio parahaemolyticus strains isolated from diarrheal patients in Beijing were dominated by O3:K6 strains, with stronger virulence. The positive rates of genes tlh and tdh were high. Vibrio parahaemolyticus strains showed high sensitivity to most antibiotics. The prevalent Vibrio parahaemolyticus strains in Beijing had various sources of clones.

[A survey on serological epidemiology of influenza A (H1N1) 2009 in Beijing].

OBJECTIVE: To investigate the immunological level against influenza A (H1N1) 2009 in Beijing and provide evidence to evaluate the developing trend of the disease. METHODS: Between Nov. 27, 2009 and Dec. 23, 2009, subjects were randomly selected from patients in hospitals (infectious and respiratory diseases related departments were excluded), volunteers in blood donation center and healthy subjects attending the physical examination center. Questionnaire survey was conducted and serum samples were collected to detect the hemagglutination-inhibition (HI) antibody against influenza A (H1N1) 2009 virus. RESULTS: 856 subjects participated in this survey, and 127 showed positive HI antibody to this pandemic virus. The proportions of sero-positivity among 0 - 5, 6 - 17, 18 - 55, ≥ 56 year olds were 14.5%, 19.4%, 17.4% and 8.0% respectively (P = 0.009). There was no significant difference in the sero-positivity between males and females (P = 0.693). The age-adjusted positive rate was 15.8% in the population of Beijing. By multivariate logistic regression analysis, factors as age, acute respiratory symptoms and the rate of pandemic (H1N1) 2009 vaccination were significantly associated with sero-positivity of HI antibody to the influenza A (H1N1) 2009 virus. CONCLUSION: Above 15% of the population in Beijing showed protective antibody against influenza A (H1N1) 2009 virus, indicating the development of immunological barrier to this disease had been formed, to some extent.