Exploration of transmission chain and prevention of the recurrence of coronavirus disease 2019 in Heilongjiang Province due to inhospital transmission

The coronavirus disease 2019(COVID-19)epidemic is a major public health emergency characterized by fast spread,a wide range of infections,and enormous control difficulty.Since the end of December 2019,Wuhan has become the first core infection area of China's COVID-19 outbreak.Since March 2020,the domestic worst-hit areas have moved to the Heilongjiang Province due to the increased number of imported COVID-19 cases.Herein,we reported the major COVID-19 outbreak,which caused a rebound of the epidemic in Harbin,China.After the rebound,different levels of causes for the recurrence of COVID-19,including citylevel,hospital-level,and medical staff-level cause,were investigated.Meanwhile,corresponding countermeasures to prevent the recurrence of the epidemic were also carried out on the city level,hospital level,and medical staff level,which eventually showed the effect of infection control function in a pandemic.In this study,we described the complete transmission chain,analyzed the causes of the outbreak,and proposed corresponding countermeasures from our practical clinical experience,which can be used as a valuable reference for COVID-19 control.

Reconstructing early transmission networks of SARS-CoV-2 using a genomic mutation model

The coronavirus disease 2019(COVID-19)pandemic has greatly damaged human society,but the origins and early transmission patterns of the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)pathogen remain unclear.Here,we reconstructed the transmission networks of SARS-CoV-2 during the first three and six months since its first report based on ancestor-offspring relationships using BANAL-52-referenced mutations.We explored the position(i.e.,root,middle,or tip)of early detected samples in the evolutionary tree of SARS-CoV-2.In total,6799 transmission chains and 1766 transmission networks were reconstructed,with chain lengths ranging from 1-9 nodes.The root node samples of the 1766 transmission networks were from 58 countries or regions and showed no common ancestor,indicating the occurrence of many independent or parallel transmissions of SARS-CoV-2 when first detected(i.e.,all samples were located at the tip position of the evolutionary tree).No root node sample was found in any sample(n=31,all from the Chinese mainland)collected in the first 15 days from 24 December 2019.Results using six-month data or RaTG13-referenced mutation data were similar.The reconstruction method was verified using a simulation approach.Our results suggest that SARS-CoV-2 may have already been spreading independently worldwide before the outbreak of COVID-19 in Wuhan,China.Thus,a comprehensive global survey of human and animal samples is essential to explore the origins of SARS-CoV-2 and its natural reservoirs and hosts.

Study on force chain evolution of rice straw with different length during vibrational compression

This paper explores the mechanism of force chain evolution and voidage change under vibrational and non-vibrational compression conditions of rice straw of different lengths.Simulations were used to explore the force chain evolution and voidage variation mechanism under different conditions.The re-sults show that under non-vibrational compression,the strong force chain passes from top to bottom in vertical direction and from center to periphery in tangential direction.Under vibrational compression,the force chain passes from top and bottom to center in vertical direction and the force chain evolves from outer ring to interior and exterior in tangential direction.The number of strong chains,voidage and standard deviation of the mean pressure under vibratory compression are lower than the values under non-vibratory compression.Vibration promotes stress transfer and enhancement,velocity enhancement and density enhancement.This study analyzes the mechanical properties of different lengths straw during vibrational and non-vibrational compression from a detailed viewpoint.

Infectivity of Severe Acute Respiratory Syndrome during Its Incubation Period

Objective To evaluate the infectivity of severe acute respiratory syndrome （SARS） during its incubation period by investigating chains of transmission and individuals isolated for medical observation with a view to providing scientific evidence for updating protocols of medical isolation. Methods Individuals related with the two SARS chains of transmission in Beijing in 2003 and a group of individuals isolated for medical observation in Haidian district of Beijing during the SARS outbreak were selected as subjects of study. Contactors with SARS patients and those with symptom development following the contacts were investigated via questionnaire. Serum samples were collected from super transmitters and tested for SARS-CoV antibody by neutralization test and enzyme linked immunosorbent assay （ELISA）. Results A total of 1 112 contactors were investigated in three surveys. Of them, 669 had a history of close contact with symptomatic SARS patients, 101 developed symptoms with a rate of 15.1%, 363 had a history of close contact with patients in their incubation period, none of whom developed symptoms （0%）. Serum samples were collected fi＇om 32 highly-exposed individuals, of whom 13 developing SARS symptoms atter contact had serum samples positive for SARS-CoV antibody. Samples collected from the asymptomatic contactors were all negative for SARS-CoV antibody. Conclusion SARS cases are infectious only during their symptomatic period and are non-infectious during the incubation period. Isolation for medical observation should be placed for individuals who are in close contact with symptomatic SARS patients. The results of our study are of decisive significance for the Ministry of Health to the definition of SARS close contactor.

Antibiotic resistome mostly relates to bacterial taxonomy along a suburban transmission chain

Antibiotic resistance genes comprising antibiotic resistome are of great concern due to their increase in the environment.Recent evidence of shared resistomes between soils and animal husbandry has imposed potential risks to human health.However,the correlation between a given community’s resistome and bacterial taxonomic composition is controversial.Here,a transmission chain of resistomes from swine manure to compost and compost-amended soil were analyzed in five suburban areas of Beijing,China,with unamended agricultural soils as control soils.Antibiotic resistomes and bacterial taxonomic compositions were distinct between(I)manure and compost;and(II)compost-amended and control soils.In manure,compost,and compost-amended soils,theβ-diversity of the resistome and bacterial taxonomic composition was significantly correlated,while no correlation was detected in control soils.Bacterial taxonomic composition explained 36.0%of total variations of the resistome composition,much higher than environmental factors.Together,those results demonstrated that antibiotic resistome was closely related to bacterial taxonomic composition along the suburban transmission chain.

Comparison of clinical course of patients with severe acute respiratory syndrome among the multiple generations of nosocomial transmission

Background Severe acute respiratory syndrome (SARS) is characterized by both an atypical pneumonia and efficient nosocomial transmissin. However,it remains unknown whether the infectivity and the virulence of the pathogen will change throughout the successive transmission. This study was conducted to compare the clinical features and management regimens of patients with SARS among the multiple generations from nosocomial transmission initiated by a super-spreader. Methods The clinical data of 84 epidemiologically-linked SARS patients from a hospital outbreak were retrospectively studied. All patients,in whom a clear-cut transmission generation could be noted,had a direct or indirect exposure to the index patient and the epidemic successively propagated through the multiple generations of cases within a short period of time. Results There were 66 women and 18 men with mean age of (29.2 ± 10.3) years in this cluster;and 96.4% of whom were health care workers. Detailed contact tracing identified 35 (41.7%) first-generation cases,34 (40.5%) second-generation cases,and 15 (17.8%) third-generation cases. No statistical differences among the multiple generations of transmission were found in terms of age,gender,incubation period and length of hospital stay. With the advanced transmission generations,the initial temperature lowered,the number of cases with dry cough decreased. There were no statistical differences in the peak temperature and duration of fever,other accompanying symptoms,leucopenia;however,the time from initial pulmonary infiltrates to radiographic recovery shortened ( P <0.05). No differences were found in maximum number of lung fields involved,duration from the onset of fever to the occurrence of pulmonary infiltrates and time from the initial pulmonary infiltrate to its peak among the multiple transmission generations ( P >0.05). No statistical differences were found in modes of oxygen therapy and sorts of antibiotics prescribed among the various transmission generations ( P >0.05);however, as with the advanced transmission generations,the number of cases prescribed with methylprednisolone,human γ-globulin,interferon-α,antiviral drugs (oral ribavirin or oseltamivir) increased ( P <0.05) and time from admission to starting these medication shortened ( P <0.05). Conclusions There is no evidence that SARS infection will evolve or transmit within a fashion that permits it to become less powerful throughout the successive transmission within a short time.