Objective Based on an investigation of an outbreak of COVID-19 in Nanchang, to understand the transmission process, analyze the infectivity of the cases in incubation period and asymptomatic carrier, and evaluate the transmission risks in different exposures. Methods Case investigation was based on the traditional epidemiological survey, combined with analysis based on big data about population movement trajectories. Transmission chain was identified to indicate transmission relationship. learn more Results A total of 27 cases were found in this cluster epidemic, including 25 confirmed cases, 1 suspected case (index case) and 1 asymptomatic carrier. A total of 347 close contacts were found. The secondary attack rate was 7.2% (25/347). The infection rates in close contacts of the first, second, third and fourth generation cases were 52.6% (10/19), 6.1% (13/213), 2.3% (2/88) and 0.0% (0/27), respectively. Asymptomatic carrier caused household transmission. The infection rates in close contacts after having meals, sharing rooms/beds, having work contacts, having neighbor contacts, having same time medical services or sharing wards and sharing vehicles with the patients were 10.6%(17/160), 10.0%(20/201), 5.3%(5/94), 0.0%(0/30), 0.0%(0/18) and 0.0%(0/17), respectively. Conclusions The infection source of this cluster epidemic was a suspected case from Wuhan. Analysis based on big data about population movement trajectories can help to search the cases and close contacts accurately. The proposed epidemic prevention and control measures based on this investigation were effective.Objective To analyze the epidemiological characteristics of the cases firstly reported as “asymptomatic infection of COVID-19” in Guangdong province. Methods The follow-up observation method was used to continuously track and observe the cases firstly reported as “asymptomatic patients with COVID-19” in Guangdong province from January 14 to March 31, 2020. The epidemiological data of the cases were collected to analyze their epidemiological characteristics, outcome and influencing factors. Results From January 14 to March 31, 2020, a total of 325 cases were firstly reported as “asymptomatic infections of COVID-19” in Guangdong province. The epidemic curve of asymptomatic infection cases was similar to that of confirmed cases, and it had two peaks. The first peak was from January 27 to February 5, and the second peak was from March 17 to March 26. Of the 325 cases, 184 (56.6%) were subsequently converted to confirmed cases. These cases were defined as incubation period asymptomatic infection cases. The age medtic infection cases to confirmed cases, to which more attention should be paid. Further serological investigations are needed to provide a basis for the development of COVID-19 prevention and control strategies.The COVID-19 pandemic is the defining global health crisis and the greatest challenge that we are currently facing. The key to the management of infectious diseases worldwide is to abide by international regulations and conduct international cooperation in pursuit of common interests and values. WHO is the specialized international organization, under the United Nations system, to manage and control the spread of diseases. This study Summecrizes the WHO’s response mechanisms for infectious diseases, response measures and the direction of efforts to combat COVID-19, with a view to provide advices for the control of COVID-19 pandemic.The central air conditioning ventilation system plays an important role in the air circulation of buildings such as centralized isolation medical observation points and general public buildings. In order to meet the requirements of COVID-19 epidemic prevention and control, Beijing Preventive Medicine Association organized Beijing CDC and other professional institutes to write up the group standard entitled “Technical specification for health risk investigation of central air conditioning ventilation system during the COVID-19 epidemic (T/BPMA 0006-2020)” . According to the particularity of central air conditioning ventilation system risk control during the outbreak of similar respiratory infectious diseases, based on current laws and regulations and the principle of scientific, practical, consistency and normative, 8 key points of risk investigations were summarized, which were the location of fresh air outlet, air conditioning mode, air return mode, air system, air distribution, fresh air volume, exhaust and air conditioner components. The contents, process, method, data analysis and conclusion of the investigation implementation were also defined and unified. It could standardize and guide institutions such as disease control and health supervision to carry out relevant risk managements, and provided solutions and technical supports for such major public health emergencies in city operations.Biosafety is an important guarantee of the new coronavirus laboratory test. The accident treatment of sample overflow and sprinkle is a necessary part of the emergency plan for testing activities. Beijing Preventive Medicine Association coordinated biosafety experts of COVID-19 laboratories from Beijing CDC, to write up “The standard for handling of accidents of corona virus disease 2019 sample (T/BPMA 0005-2020)” . The group standard was based on the guidelines of China and WHO, and combined with the practical experience of COVID-19 epidemic and the principle of “scientific, normative, applicable and feasible” . Through all kinds of risk Assessment, it included the spillover of samples caused by the packing of COVID-19 (highly pathogenic) samples, the overflow and sprinkle in the laboratory during the detection operation, and the spillage accident occurred during the transfer of samples in the same building. The standard could guide and standardize the handling methods of accidental overflow and sprinkle that may occur in the SARS-CoV-2 testing laboratories in the city.This work investigates polyvinylidene fluoride (PVDF) membrane modification to enhance its hydrophilicity and antibacterial properties. PVDF membranes were coated with nanoparticles of titanium dioxide (TiO2-NP) and silver (AgNP) at different concentrations and coating times and characterized for their porosity, morphology, chemical functional groups and composition changes. The results showed the successfully modified PVDF membranes containing TiO2-NP and AgNP on their surfaces. When the coating time was increased from 8 to 24 h, the compositions of Ti and Ag of the modified membranes were increased from 1.39 ± 0.13 to 4.29 ± 0.16 and from 1.03 ± 0.07 to 3.62 ± 0.08, respectively. The water contact angle of the membranes was decreased with increasing the coating time and TiO2-NP/AgNP ratio. The surface roughness and permeate fluxes of coated membranes were increased due to increased hydrophilicity. Antimicrobial and antifouling properties were investigated by the reduction of Escherichia coli cells and the inhibition of biofilm formation on the membrane surface, respectively.