Household transmission of SARS-CoV-2 during the Omicron wave in Shanghai, China: a case-ascertained study

BackgroundSince late 2021, the highly transmissible SARS-CoV-2 Omicron variant has driven a new surge of infections across the world. We used a case-ascertained study to determine the features of household transmission of SARS-CoV-2 Omicron variant in Shanghai, China. MethodsWe collected detailed information on 323 pediatric cases and their 951 household members in April 2022 during the Omicron outbreak. All household members received consecutively intensive RT-PCR testing for SARS-CoV-2 and routine symptom monitoring within 14 days after exposure to a confirmed case. We described the characteristics of study participants and estimated the transmission parameters. Both secondary infection attack rates (SARI) and secondary clinical attack rates (SARC) among adult household contacts were computed, through which the transmission heterogeneities in infectivity and susceptibility were characterized and the vaccine effectiveness were estimated. ResultsWe estimated the mean incubation period of SARS-CoV-2 Omicron variant to be 4.6 (median: 4.4, IQR: 3.1-6.0) days and the mean serial interval to be 3.9 (median:4.0, IQR: 1.4-6.5) days. The overall SARI and SARC among adult household contacts were 77.11% (95% confidence interval [CI]: 73.58%-80.63%) and 67.03% (63.09%-70.98%). We found higher household susceptibility in females, while infectivity was not significantly different in primary cases by age, sex, vaccination status and clinical severity. The estimated VEs of full vaccination was 14.8% (95% CI: 5.8%-22.9%) against Omicron infection and 21.5% (95% CI: 10.4%-31.2%) against symptomatic disease. The booster vaccination was 18.9% (95% CI: 9.0%-27.7%) and 24.3% (95% CI: 12.3%-34.7%) effective against infection and symptomatic disease, respectively. ConclusionsWe found high household transmission during the Omicron wave in Shanghai due to asymptomatic and pre-symptomatic transmission in the context of city-wide lockdown, indicating the importance of early detection and timely isolation of SARS-CoV-2 infections and quarantine of close contacts. Marginal effectiveness of inactivated vaccines against Omicron infection poses great challenge for prevention and control of the SARS-CoV-2 Omicron variant.

Epidemiological and clinical features of SARS-CoV-2 Infection in children during the outbreak of Omicron Variant in Shanghai, March 7-March 31, 2022

ObjectivesTo understand the epidemiological and clinical characteristics of pediatric SARS-CoV-2 infection during the early stage of Omicron variant outbreak in Shanghai. MethodsThis study included local COVID-19 cases <18 years in Shanghai referred to the exclusively designated hospital by the end of March 2022 since emergence of Omicron epidemic. Clinical data, epidemiological exposure and COVID-19 vaccination status were collected. Relative risks (RR) were calculated to assess the effect of vaccination on symptomatic infection and febrile disease. ResultsA total of 376 pediatric cases of COVID-19 (median age:6.0{+/-}4.2 years) were referred to the designated hospital during the period of March 7-31, including 257 (68.4%) symptomatic cases and 119 (31.6%) asymptomatic cases. Of the 307 (81.6%) children;3 years eligible for COVID-19 vaccination, 110 (40.4%) received 2-dose vaccines and 16 (4.0%) received 1-dose vaccine. The median interval between 2-dose vaccination and infection was 3.5 (IQR: 3, 4.5) months (16 days-7 months). Two-dose COVID-19 vaccination reduced the risks of symptomatic infection and febrile disease by 35% (RR 0.65, 95% CI:0.53-0.79) and 33% (RR 0.64, 95% CI: 0.51-0.81). Two hundred and sixteen (83.4%) symptomatic cases had fever (mean duration: 1.7{+/-}1.0.8 days), 104 (40.2%) had cough, 16.4% had transient leukopenia; 307 (81.6%) had an epidemiological exposure in household (69.1%), school (21.8%) and residential area (8.8%). ConclusionThe surge of pediatric COVID-19 cases and multiple transmission model reflect wide dissemination of Omicron variant in the community. Asymptomatic infection is common among Omicron-infected children. COVID-19 vaccination can offer protection against symptomatic infection and febrile disease.

Seroprevalence of serum measles antibody in children with tumor after chemotherapy / 中华传染病杂志

Objective:To investigate the serum measles antibody in children with tumor and to provide the clinical evidence for measles vaccination strategy for this special population.Methods:From January 2016 to December 2018, the blood samples of children who were diagnosed with hematological malignancy or solid tumors and received chemotherapy in the Department of Hematology or Oncology Surgery of Children′s Hospital of Fudan University were collected. Enzyme-linked immunosorbent assay was used to quantitatively detect the level of measles IgG antibody, and dynamically monitor the changes of measles antibody level during chemotherapy. Kruskal-Wallis test and chi-square test were used for statistical analysis.Results:A total of 441 children with tumors were enrolled, with the positive rate of measles antibody of 79.1%(349/441), and only 43.3%(191/441) of children had the protective level of IgG antibody. There was a statistically significant difference of the antibody protection rate in children aged<eight months old, eight months old to <two years old, two years old to <six years old, and ≥six years old ( χ2=15.647, P<0.01). There was no statistically significant difference of the protection rate of serum measles antibody between children aged two to <six years and≥six years (43.8%(95/217) vs 41.1%(58/141), P>0.05). The protection rate of serum measles antibody in children with hematological malignancy and solid tumor were 45.6%(78/171) and 41.9%(113/270), respectively, and there was no statistically significant ( P>0.05). There were 16.3%(16/98) of children who were observed to lose the pre-existing protective antibody during chemotherapy. There was no statistically significant difference of the protection rate of serum among children who had finished chemotherapy <six months, six months to <one year, one year to <two years, and ≥two years ( P>0.05). Conclusions:Serum measles antibody is below the protective level in more than 50% of children with malignancy after chemotherapy. Chemotherapy can compromise the protective antibody against measles. It is recommended for this special population to re-schedule measles vaccine after individualized evaluation to acquire the immuneprotection against measles.

A Case Series of Children With 2019 Novel Coronavirus Infection: Clinical and Epidemiological Features.

We first described the 2019 novel coronavirus infection in 10 children occurring in areas other than Wuhan. The coronavirus diseases in children are usually mild and epidemiological exposure is a key clue to recognize pediatric case. Prolonged virus shedding is observed in respiratory tract and feces at the convalescent stage.

A case-control study on diarrheagenic E .coli infection in children / 中华传染病杂志

Objective To understand the regional epidemiology and antibiotic resistance pattern of diarrheagenic E .coli infection in children ,and to clarify the pathogenic association between diarrheagenic E .coli infection and childhood diarrhea .Methods Totally 680 diarrheal children in the outpatient setting and 680 non-diarrheal control children were enrolled prospectively .The stool samples were collected and the potential enteric pathogens were detected .Minimal inhibitory concentration (MIC) method was used to determine the antimicrobial susceptibility for diarrheagenic E .coli isolates .Results The isolation rates of diarrheagenic E .coli in diarrhea group and control group were 15 .6％ and 13 .1％ ,respecitvely ,and diarrheagenic E .coli was the most commonly detected enteric bacteria .Multivariate logistic regression analysis adjusted for age suggested no clinical association between diarrhea and infection with enteropathogenic E .coli (EPEC) (aOR=1 .2 ,95％ CI:0 .8-1 .8) ,enteroadhesive E .coli (EAEC) (aOR=1 .1 ,95％ CI:0 .7 -1 .6) and enterotoxigenic E .coli (ETEC) (aOR= 1 .8 ,95％ CI:0 .5 -6 .2) . Among 199 diarrheagenic E .coli strains ,the rates of resistance to ampicillin ,tetracycline ,trimethoprim-sulfamethoxazole ,azithromycin ,and ceftriaxone were 63 .8％ ,55 .8％ ,48 .2％ ,34 .2％ and 26 .6％ , respectively ,while the rates of resistance to ciprofloxacin , amoxicillin-clavulanate and cefoxitin were 4 .5％ ,1 .5％ and 0 .5％ ,respectively .Conclusions Diarrheagenic E .coli is the most common enteric bacteria detected in the stool samples from children with and without diarrhea in this study . The pathogenic role of infections with EPEC ,EAEC and ETEC in childhood diarrhea is not determined .EHEC and EIEC are rarely detected and further studies are needed to clarify the pathogenic association between infection with EHEC ,EIEC and childhood diarrhea .

Surveillance of enteric pathogens in outpatient children with acute diarrhea / 中华传染病杂志

Objective To monitor the clinical epidemiology and etiology of acute diarrhea in children in the outpatient setting in Shanghai .Methods An active surveillance study in Children′s Hospital of Fudan University between August 2013 and July 2014 was conducted .Outpatient children with acute diarrhea were enrolled in this study and stool samples were collected .Pathogens including norovirus ,diarrheagenic Escherichia coli (DEC) , nontyphoidal Salmonella spp .(NTS),Campylobacter,Shigella,pathogenic vibrio and Yersinia enterocolitica were identified and typed .The χ2 test was used for statistical analysis .Results Of the 881 stool samples from enrolled children , the pathogens included into the target detection were identified in 246 (27 .92% ) cases . Norovirus ,DEC ,NTS ,Campylobacter and Shigella were detected in 98 (11 .12% ) cases ,74 (8 .40% ) cases , 61 (6 .92% ) cases ,34 (3 .86% ) cases and 2 (0 .23% ) cases ,respectively .Neither pathogenic vibrio nor Yersinia enterocolitica was identified .Children younger than 36 months old (3 .27% ,26/794) had a lower risk (χ2=7 .41 ,P=0 .006) of Campylobacter infection compared with older children (9 .20% ,8/87) .Vomiting (37 .76% ) and watery diarrhea (21 .34% ) were more commonly seen in children with norovirus infection;fever and mucous stool were commonly seen in diarrheal children with NTS infection (40 .98% and 21 .31% ,respectively) and Campylobacter infection (29 .41% and 26 .47% ,respectively) .Conclusion Enteric pathogens play a major role in childhood acute diarrhea in Shanghai .Continuous monitoring of enteric pathogens will be helpful for reasonable treatment and prevention of acute diarrhea in children .

Clinical and etiologic features of diarrheagenic Escherichia coli-associated diarrhea in children / 中华传染病杂志

Objective To investigate the pathotypes,epidemiological characteristics and antimicrobial resistance of diarrheagenic Escherichia coli (DEC) in children with acute bacterial diarrhea in Shanghai.Methods A total of 2 071 outpatient children with probable acute bacterial diarrhea referred to the enteric clinic of Children's Hospital of Fudan University during June 2012 to June 2014 were enrolled in our study.The stool samples were processed for routine microbiologic and biochemistry tests to identify enteric bacteria,including enteropathogenic Escherichia coli (EPEC),enterotoxigenic Escherichia coli (ETEC),enteroinvasive Escherichia coli (EIEC) and enterohemorrhagic Escherichia coli (EHEC).Kirby-Bauer method was used to identify the antibiotic sensitivity.Difference of means between groups was compared by chi-square test.Results Of 2 071 enrolled children,DEC were identified in 145 (7.0 ％)cases.148 strains were isolated with three of mix infection strains.All DEC isolates in this study included 106 (71.6％) EPEC,24 (16.2％) ETEC,16(10.8％) EIEC and 2(1.4％) EHEC.The median ages of diarrheal children with DEC infections were 14 months (range:3 months to 13 years) and 62.8％ of them were ＜2 years.Among 125 DEC isolates tested for antimicrobial susceptibility,the rates of resistance to ampicillin,trimethoprim-sulfamethoxazole,cefotaxime,cefepime,gentamicin,ceftazidime,amoxicillinclavulanate,ciprofloxacin,and ofloxacin in a descending order were 55.2％,35.2％,28.0％,27.2％,23.2％,8.8％,5.6％,4.0％ and 4.0％,respectively.Resistance rates of EIEC to cefotaxime,cefepime and ceftazidime were 50.0％,43.8％ and 25.0％,respectively,which were higher than those of EPEC,ETEC and EHEC.Conclusion DEC is the important enteric bacteria that causes bacterial diarrhea in children in this study.